QC 813

U6

SB b34 257

W.B.Na.235.

U. S. DEPARTMENT OF AGRICULTURE,

WEATHER BUREAU.

CHARLES F. MARVIN, CfflBF.

PSYCHROMETRIC TABLES

FOR OBTAINING THE

VAPOR PRESSURE, RELATIVE HUMIDITY, AND TEMPERATURE OF THE DEW-POINT.

PROM READINGS OF THE WET AND DRY BULB THERMOMETERS.

BY O. F. MAHVIN.

WASHINGTON:

GOVERNMENT PRINTING OFFICE. 1915.

W. B. N 3, 235.

U. S. DEPARTMENT OF AGRICULTURE,

WEATHER BUREAU. CHARLES F. MARVIN, CHIEF.

PSYCHROMETRIC TABLES

FOR OBTAINING THE

VAPOR PRESSURE, RELATIVE HUMIDITY, AND TEMPERATURE OF THE DEW-POINT.

FROM READINGS OF THE WET AND DRY BULB THERMOMETERS.

BY O. F. MARVIN.

WASHINGTON:

GOVERNMENT PRINTING OFFICE. 1915.

U. S. DEPARTMENT OF AGRICULTURE,

WEATHER BUREAU, WASHINGTON, l). C., October 5, 1915.

These tables were first published in 1900 and were reprinted in 1910 with the addition of a brief appendix. The edition of 1910 was reprinted in 1912 and is now again reprinted without any alterations,

CHARLES F. MARVIN,

Chief of Bureau* (3)

794865

PSYCHROMETRIC TABLES

MEASUREMENT OF ATMOSPHERIC MOISTURE. — The quantity of moisture mixed with, the air under different conditions of tempera- ture and degree of saturation may be measured in several dis- tinctly different ways. Many of these, however, are not practicable methods for daily observations, or are not sufficiently accurate. Probably the most convenient of all methods and the one most generally employed is to observe the temperature of evaporation — that is, the difference between the temperatures indicated by wet and dry-bulb thermometers. The most reliable instrument for this purpose is the sling, or whirled psychrometer. In special cases rotary fans, or other means, may be employed to move the air rapidly over the thermometer bulbs. In any case satisfactory results can-not be obtained from observations in relatively stag- nant air. A strong ventilation is absolutely necessary to accuracy.

SLING PSYCHROMETER. — This instrument consists of a pair of thermometers, provided with a handle as shown in fig. 1, which permits the thermometers to be whirled rapidly, the bulbs being thereby strongly affected by the temperature of and moisture in the air. The bulb of the lower of the two thermometers is covered with thin muslin, which is wet at the time an observation is made.

THE WET-BULB. — It is important that the muslin covering for the wet-bulb be kept in good condition. The evaporation of the water from the muslin always leaves in its meshes a small quantity of solid material, which sooner or later somewhat stiffens the mus- lin so that it does not readily take up water. This will be the case if the muslin does not readily become wet after being dipped in water. On this account it is desirable to use as pure water as possible, and also to renew the muslin from time to time. New muslin should always be washed to remove sizing, etc., before being used. A small rectangular piece wide enough to go about one and one-third times around the bulb, and long enough to cover the bulb and that part of the stem below the metal back, is cut out, thoroughly wetted in clean water, and neatly fitted around the thermometer. It is tied first around the bulb at the top, using a moderately strong thread. A loop of thread to form a knot is next placed around the bottom of the "bulb, just where it begins to round off. As this knot is drawn tighter and tighter the thread sjlips off the rounded end of the bulb and neatly stretches the mus- lin covering with it, at the same time securing the latter at the bottom.

(5)

6

To MAK^ AN OBSERVATION. — The so-called wet-bulb is thoroughly saturated with water by dipping it into a small cup or wide-mouthed bottle. The thermometers are then whirled rapidly for fifteen or twenty seconds; stopped and quickly read, the wet-bulb first. This reading is kept in mind, the psychrome- ter immediately whirled again and a second reading taken. This is repeated three or four times, or more, if necessary, until at least two successive readings of the wet-bulb are found to agree very closely, thereby showing that it has reached its lowest tem- perature. A minute or more is generally required to secure the correct temperature.

When the air temperature is near the freezing point it very often happens that the temperature of the wet-bulb will fall several degrees below freez- ing point, but the water will still remain in the liquid state. No error results from this, provided the minimum temperature is reached. If, however, as frequently happens, the water suddenly freezes, a large amount of heat is liberated, and the tem- perature of the wet-bulb immediately becomes 32°. In such cases it is necessary to continue the whirl- ing until the ice-covered bulb has reached a mini- mum temperature.

WHIRLING AND STOPPING THE PSYCHROMETER. — It is impossible to effectually describe these move- ments. The arm is held with the forearm about horizontal, and the hand well in front. A peculiar swing starts the thermometers whirling, and after- ward the motion is kept up by only a slight but very regular action of the wrist, in harmony with the whirling thermometers. The rate should be a natural one, so as to be easily and regularly main- tained. If too fast, or irregular, the thermometers may be jerked about in a violent and dangerous manner.

The stopping of the psychrometer, even at the very highest rates, can be perfectly accomplished in a single revolution, when one has learned the knack. This is only acquired by practice, and con- sists of a quick swing of the forearm by which the hand also describes a circular path, and, as it were, follows after the thermometers in a peculiar man- ner that wholly overcomes their circular motion

FlG. 1.— StINO PSY- CH ROM ETEK.

without the slightest shock or jerk. The thermometers may, with- out very great danger, be allowed simply to stop themselves ; the final motion in such a case will generally be quite jerky, but, unless the instrument is allowed to fall on the arm, or strikes some object, no injury should result.

EXPOSURE. — While the psychrometer will give quite accurate indications, even in the bright sunshine, yet observations so made are not without some error, and, where greater accuracy is desired, the psychrometer should be whirled in the shade of a building or tree, or, as may sometimes be necessary, under an umbrella. In all cases there should be perfectly free circulation of the air, and the observer should face the wind, whirling the psychrometer in front of his body. It is a good plan, while whirling, to step back and forth a few steps to further prevent the presence of the observer's body from giving rise to erroneous observations.

DEW-POINT APPARATUS. — The apparatus shown in .fig. 2 is a modified form of Regnault's apparatus, and serves to determine directly the temperature of the dew-point. It consists essentially of a thin polished silver tube, a, cemented upon the lower end of a longer glass tube, as shown. The stopper closing the upper end of this tube is fitted with two lateral tubes of hard rubber, b and c, and carries a delicate thermometer, the bulb of which is placed near the center of the silver tube. The tube b extends to the bot- tom of the silver tube; c projects but a short distance through the cork. A rubber aspirating apparatus, as shown, is connected with the tube fr, and a long tube joined to c serves to carry off the fumes generated in the apparatus. The glass tube is held in a clamp faced with cork, which largely intercepts the transfer of heat.

Observations are made by filling the silver cup with sulphuric ether, or similar volatile liquid, which is caused to evaporate and cool the silver cup in the desired manner by manipulating the aspiration bulb. At the proper point of cooling, a deposit of dew is seen to form on the polished silver surface. The object is to ascertain accurately the temperature at which the dew will just deposit. For this purpose it is necessary that the temperature be lowered very slowly at the critical point, also that there be plenty of liquid in the cup and that it be agitated sufficiently to have a uniform temperature throughout. Finally, the surface of the silver must be perfectly clean and in a favorable light, so that the faintest deposition of dew is at once visible. The temperature shown by the thermometer at this moment may be regarded as the temperature of the dew-point.

In order that the presence of the observer shall not affect the moisture contents of the air in the vicinity of the cup during an observation, it is necessary that in breathing he exhale through a

suitable tube which will conduct the moist air from his lungs to a sufficient distance. It is further advisable that a very gentle motion be given to the air near the cup by use of an ordinary fan. For the greatest accuracy, the cup should be allowed to warm up and the deposition of dew formed several times in succession, a reading of the temperature being made at each deposition.

FIG. 2. DEW-POINT APPABATUS.

FAULTY CONCEPTIONS.— A false notion that the air has a cer- tain capacity for moisture is widely prevalent, and is perpetuated by all such expressions as ' ' The air is partly saturated with moist- ure," ;' Weight of aqueous vapor in a cubic foot of saturated air" etc.

It should always be clearly observed that the presence of the moisture in any given space is independent of the presence or

absence of air in the same space except that the air retards the diffusion of the vapor particles. It is more correct to say, in the above cases, that the space is partly saturated with moisture, or that the moisture is in a partly saturated condition or is super- heated. By all means use the phrase ' ' Weight of a cubic foot of saturated aqueous vapor," not "Weight of aqueous vapor in a cubic foot of saturated air."

THE PSYCHROMETRIC FORMULA. — The values of relative humid- ity, and the temperature of dew-points given in the accompanying tables, have been computed by means of the following formula, deduced by Professor Ferrel,*

(

in which t and t' are the temperatures of the dry and wet bulb thermometers, P is the barometric pressure of the air in inches, all corrections having been applied, and e' is the maximum or sat- uration pressure of aqueous vapor at the temperature t' of the wet bulb.

The solution of the equation gives e, the pressure of the aqueous vapor corresponding to the observed temperatures t and t'.

The constants of the formula were deduced from a large series of experiments made by the writer in Colorado Springs, Colo., and at different elevations on Pike's Peak. These experiments were supplemented by similar observations made in Washington by Prof. H. A. Hazen and the writer, and include a considerable number of experiments at temperatures below the freezing point by Professor Hazen.

In the experiments referred to, the sling, or whirled psychrome- ter, was employed to ascertain the difference, t — t\ between the wet and dry bulb temperatures, and simultaneous determinations were also made of the temperature of the dew-point by means of modified forms of the Regnault and the Alluard dew-point appara- tus. The modified Regnault apparatus is described in a preceding paragraph and shown in fig. 2.

The formula and tables are, therefore, strictly applicable only to wet and dry bulb temperatures as determined by means of the sling, or whirled psychrometer, or some equivalent form of appa- ratus, in which the wet bulb especially is subjected to a strong current of air, the velocity of which is not less than 15 feet per second.

MAXIMUM PRESSURE OF AQUEOUS VAPOR. — The amount of saturated aqueous vapor that can exist in any given space depends entirely upon the temperature. It appears that the vapor may be

*Annual report of the Chief Signal Officer, 1886; Appendix 24, pp. 233-259.

10

supersaturated under certain peculiar conditions, but this is a special and an unstable state of nature which need not be consid- ered in the present connection. When the vapor is saturated, it will exert a certain pressure which varies with the temperature and which so-called "maximum pressure " has been measured with greater or less precision over a long range of temperature from about 60° below zero F. to far above the boiling point of water.

The hygrometric tables used by the Weather Bureau since 1886 have been based on the formula given above but used in a slightly modified form. The vapor pressures employed were derived from Broch's reduction of Regnault's observations.* All the values given by these tables at temperatures below the freezing point are noticeably higher than Regnault's observations. In view of this systematic discordance, and the further circumstance that Reg- nault's experiments did not include observations at the extremely low temperatures frequently recorded at Weather Bureau stations, the writer, in 1891, made a new determination of the maximum pressure of aqueous vapor at low temperatures.!

In the course of these experiments it was found an easy matter to reduce the temperature of the water employed many degrees below 32° F., without freezing it, and in these cases the vapor pressure was higher than the pressure from ice at the same temper- ature. Independent experiments in Sweden, by Julius Juhlin, at about this time, led to the same results.

A comparison of the vapor pressures derived from the several sources mentioned, show that Broch's computed values at low tem- peratures do not agree at all well with Regnault's experiments, from which they are derived, whereas the experimental results of Regnault, Juhlin, and the writer agree very closely.

At temperatures below 32° F., therefore, it has been considered necessary to reject Broch's values, and the vapor pressures over ice, as deduced from the writer's experiments, have been used in the calculation of the following tables. These values are given in the several columns headed "Vapor pressure, e." At tempera- tures above 32° F., the values taken from Broch's tables are em- ployed, and likewise recorded in the appropriate columns headed "Vapor pressure, e." At 32° F., the value for the vapor pressure found by the writer from the mean of a large number of experi- ments, was identical with that of Broch ; hence there is no break in the continuity of the two tables at the point of junction.

The atmospheric pressure at the great majority of Weather Bu- reau stations ranges from 28 to 31 inches, and to obviate the neces- sity of any correction for pressure or interpolations two tables

* Travaux et Memoires du Bureau International des Poids et Mesures, Tome I. \ Annual report of the Chief Signal Officer, 1891 ; Appendix No. 10, pp. 351-383.

11

for pressures of 29 inches and 30 inches, respectively, have been computed. Considerable portions of these two tables are simply- duplicate impressions from the same electrotypes, but this duplica- tion not only secures accuracy but greatly facilitates reduction of observation at numerous stations. Three additional tables at 27, 25, and 23 inches, respectively, have been added for the reduction of observations at correspondingly elevated stations.

VAPOR PRESSURES AT HIGH TEMPERATURES. — Table XI is added at the end of the series in response to numerous requests for tables giving relative humidities at high temperatures, and gives the vapor pressure, in inches of mercury, for each degree of temperature from 100° to 445° F. The values in this table, up to and including 212°, have been taken from Broch's tables. Above 212° the values are reproduced in English units from Regnault's original tables.* Broch's values have all been reduced to standard temperature and nianometric units at sea level and latitude 45°; Regnault's values are for the latitude and elevation of his labora- tory in Paris, viz, 48° 50' 14" north latitude, and 60 meters (197 feet) above the level of the sea. There is thus a slight discord- ance between the different parts of the table, but the effect is very small.

The psychrometric formula given above can not be used for tem- peratures higher than 130° to 140° F., for the reason that the con- stants of the equation have been deduced from experiments only at ordinary temperatures, and the use of the formula for the reductions of observations at high temperatures would give only coarsely approximate results.

Probably the most available method of determining humidities at high temperatures is by use of the dew-point apparatus described on page 7, which is susceptible of a great variety of forms, and gives directly the temperature of the dew-point. Table XI then gives the corresponding vapor pressure. The relative humidity is obtained by dividing this pressure by the pressure given in Table XI corresponding to the air temperature. For example, suppose it is found the temperature of the dew-point of the air in a drying oven is 115°, and that the temperature of the air is 205°. From Table XI the vapor pressure at 115° is 2.975 inches, and at 205° is 25.99 inches, hence the relative humidity is 2.975 -4- 25.99 = 11 per cent.

THE WEIGHT OF AQUEOUS VAPOR (ABSOLUTE HUMIDITY).— The weight of a cubic foot of aqueous vapor at different temper- atures and percentages of saturation is sometimes called the abso- lute humidity.

* Memoires de L'Academie des Sciences de L'lnstitute de France, Tome XXI, 1847.

12

Saturated aqueous vapor is but little more than half as heavy as the same volume of dry air under like conditions of temperature and pressure. In all ordinary computations it is assumed that the expansion and contraction of partially saturated aqueous vapor is in accordance with the same laws as apply to air and ordinary gases, which do not easily condense to the liquid state.

The adopted density of saturated aqueous vapor is not deter- mined directly from experiment, but is deduced theoretically from the observed fact that two volumes of hydrogen and one of oxy- gen, combine to produce two volumes of water vapor.

The weights of unit volumes of hydrogen, oxygen, and dry air are accurately known, from which the specific gravity of aqueous vapor is found to be 0.6221.

If English units of temperature, pressure, and weight are used, we find the weight of a cubic foot of saturated aqueous vapor in grains is :

F' L1-7449~l + 0.002037 (*- 32)'

This formula gives the weights found in the column headed " 100 " in Table XII.

USE OF TABLES EXPLAINED.

In reducing psychrometic observations, regard should be had to the atmospheric pressure at the time, and results deduced from the tables based on a pressure nearest that observed. Interpola- tion for intermediate pressures need not be made, arid when the pressure is not observed, an approximate value, known to be appropriate to the particular elevation of the point of observation, may be employed.

The psychrometric observations made at Weather Bureau sta- tions will be reduced by means of the tables based on an air pres- sure which is numerically nearest the average or normal station pressure, and detached copies of appropriate tables for the several stations will be furnished for the convenience of observers in their daily work.

The temperatures t and t' of the wet and dry bulb thermometers will be read, and the difference t — t' computed to the nearest tenth of a degree. It is desired that the dew-point especially be taken out to the nearest whole degree, and the tables have been expanded with a view to obviating difficult interpolations. In some cases, however, double interpolations must be considered, but the proper result can often be obtained by simple inspection. When the air is very dry, however, a careful calculation is necessary.

13

An examination of the dew-point tables especially will show that diagonal lines exist, inclining downward and to the right, along which the tabulated values of the dew-points are constant or change very little. As a result of this circumstance, when the observed values of air temperature and t — t' fall even roughly midway between the values given in the arguments of the table, double interpolation will, in general, not be required, as the cor- rect result will be obtained by dropping both intermediate frac- tions, even where they exceed half the interval — that is, take out the dew-point corresponding to the arguments next lower than the air temperature and t — t' observed.

When one of the observed quantities is quite near a tabulated value, the latter will be used, and the interpolation, if any is required, based on the other quantity only.

When the air is very dry the successive values in the table differ so much that carefully calculated interpolations will often be required.

The following examples of the use of the tables illustrate how the foregoing principles are applied :

EXAMPLE No. 1.— AIR PRESSURE, 29.7 INCHES.

Air temperature, £=75.0°.

Depression of the wet bulb, (£-0 = 9.5°.

In this case the table for 30 inches air pressure should be used, and we find on page 18, opposite 75° in column 9.5° : Dew point= 60°.

On this same page, opposite 60° under the column e, we find : Vapor pressure, e=0.$17.

Finally, on page 58, opposit 75° in column 9.5°, we find: Relative humidity =60 per cent.

EXAMPLE No. 2.— AIR PRESSURE, 25.8 INCHES.

Air temperature, £=67.8°.

Depression of the wet bulb, (t—f) = 3. 2°.

In this case the table for 25 inches on page 43 must be used, and the tabulated values which must be considered are :

	3.0°.	3.5'.
67° _	63	62
68°	64	63

14

A double interpolation seems to be required in a case of this kind, but it will be observed that if we drop both the intermediate frac- tions and take the dew-point corresponding to air temperature, 67°, and £—£'=3°, we get dew-point 63°, which is the correct result to the nearest degree. We thus have for the complete reduction of this observation :

Dew-point=63°.

Vapor pressure =0.575.

Relative humidity— 85 per cent.

EXAMPLE No. 3.

The following example of the use of Table XII indicates how interpolation for intermediate percentages of saturation may be effected :

What is the weight of vapor in a cubic foot corresponding to a temperature of 70° and a relative humidity of 83 per cent?

At 70° and 80 per cent the weight is.. 6.384 grains.

The additional weight for 3 per cent is TV the weight for 30 per cent, viz _. .2394 grains.

Hence, the weight at 70° and 83 per cent is. . _ 6. 623 grains.

[For additional notes, see Appendix, page 85.]

16

TABLE I. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 30.0 inches.

Air temp. t	Vapor press. e	Depression of wet-bulb thermometer (t — <').
.2	.4	.6	.8	1.0 1.2	1.4	1.6	1.8	2.0 2.2	2.4	2.6	2.8	3.0
—40 —39 00	.0039 41 A A	—50 A(\					J		J		(«-O
— Go -37	44 46	— '4y -48									.1	.2	.3	.4	.5
—36	48	—46
—35	.0051	-45					-60	.0010	-50	.0021	-60
—34	54	—43	—59				-59	11	-49	22	-58
-33	57	-42	-56				—58	12	-48	24	—56
—32	61	—40	—53				-57	13	-47	26	-55
-31	65	-38	-50				-56	13	-46	27	-53
—30	.0069	-36	—47				-55	.0015	-45	.0029	-51
—29	74	—35	—45				-54	16	-44	31	—50	-60
-28 -27 -26	78 83 89	-33 -32 -30	-42 -40 -38	-58 -54 -50			-53 -52 -51	17 18 .0019	-43 -42 -41	33 35 37	-49 -48 -46	-58 -56 -54
—25 -24	.0094 .0100	-29 —28	—36 —34	-46 —43	—60		—40 -39	. 0039 41	—45 -44	—52 -50
-23	106	-27	-32	-40	-54		-38	44	--43	-49	-59
—22	112	—26	—31	-38	-49		-37	48	-42	-48	-56
-21	119	-25	-29	-35	-45		—36	48	-41	-46	—54
-20	.0126	--23	-28	-33	-42	-57				-35	.0051	-40	-45	-51
-19	133	-22	—26	-31	-39	-51				-34	54	-38	-43	-49	-59
— 18	141	—21	—25	—29	—36	—46				-33	57	-37	-42	-47	-56
-17	150	-20	-23	-28	-33	-42	-59			—32	61	-35	-40	-46	-53
-16	159	-19	-22	-26	-31	-38	-51			-31	65	-34	-38	-44	-50	-60
-15	.0168	-18	-21	-24	-29	-35	-45			-30	.0069	-33	-36	-42	-47	-56
-14	178	-Ifi	-19	-23	-27	-32	-40	—56
-13 -12	188 199	-15 -14	-18 -17	-21 -20	-25 -23	-30 -27	-36 -33	-48 -43	-59
-11	210	-13	-16	-18	-22	-25	-30	-38	-50
-10	.0222	-12	-14	-17	-20	-24	-28	-33	-44
- 9	234	-11	-13	-16	-18	-22	-26	-30	-38	-51
- 8	247	-10	-12	-14	-17	-20	-24	-28	-34	-44
- 7	260	- 9	-11	-13	-16	—18	-22	—26	—31	-38	-51
- 6	275	- 8	-10	-12	-14	-17	-20	-23	-28	-33	-44
- 5	.0291	- 7	- 8	-10	-13	-15	—18	-21	-25	-30	-37	-50
- 4	307	- 6	- 7	- 9	-11	-14	-16	-19	-22	-27	-32	-42	-59
— 3	325	- 4	- 6	— 8	-10	—12	—14	-17	-20	-24	-29	-35	-47
- 2	344	- 3	- 5	- 7	- 8	-10	-13	-15	-18	-21	-25	-30	-38	-53
- 1	363	- 2	A	- 5	- 7	— 9	-11	-13	-16	-19	-22	-27	-32	-42	-60
0	.0383	- 1	- 3	4	- 6	7	— 9	-12	-14	-17	-20	-23	-28	-35	-46
H 1	403	± 0	- 2	- 3	- 4	- 6	— 8	-10	-12	-15	-17	-20	-25	-30	-37	-50
2	423	+- 1	- 1	- 2	- 3	- 5	- 6	- 8	-10	-13	-15	-18	-21	-26	-31	-40
3	444	2	+ 1	- 1	- 2	A	- 5	- 7	- 9	-11	-13	-16	-19	-22	—27	-32
4	467	3	2	± 0	- 1	- 2	- 4	- 5	- 7	- 9	-11	—14	-16	-19	-23	-28
5	.0491	4	3	+ 1	± 0	- 1	- 3	- 4	- 6	- 7	- 9	-12	-14	-17	-20	-24
6	515	5	4	3	+ 1	± 0	- 1	- 3	- 4	- 6	- 8	-10	-12	-15	-17	-21
7	542	6	5	4	2	+ 1	± 0	- 1	— 3	A	- 6	— 8	-10	-12	-15	-18
8	570	7	6	5	4	3	+ 1	± 0	- 2	- 3	- 6	- 6	- 8	-10	-13	-15
9	600	8	7	6	5	4	3	+ 1	± o	- 2	— 3	- 5	- 6	— 8	-10	-13
10	.0631	9	8	7	6	5	4	3	+ 1	± 0	- 2	- 3	- 5	- 6	- 8	-10
11	665	10	9	8	7	6	5	4	3	+ 1	± 0	- 1	- 3	- 4	— 6	Q
12	699	11	10	9	8	7	6	5	4	3	+ 2	± 0	- 1	- 3	- 4	- fl
13	735	12	11	11	10	9	8	7	6	4	3	+ 2	± o	- 1	— 2	- 4
14	772	13	12	12	11	10	9	8	7	6	5	3	+ 2	+ 1	- I	- 2
15	.0810	14	13	13	12	11	10	9	8	7	6	5	4	2	+ 1	± 0
16	850	15	14	14	13	12	11	10	9	8	7	8	5	4	3	+ 1
17	891	16	15	15	14	13	12	12	11	10	9	8	7	6	4	3
18	933	17	17	16	15	14	13	13	12	11	10	9	8	7	6	5
19	.0979	18	18	17	16	15	15	14	13	12	11	10	9	8	7	6
20	.1326	19	19	18	17	16	16	15	14	13	12	12	11	10	9	8

16

TABLE I. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 30.0 inches.

Air	Depression of wet-bulb thermometer (<—<')•
temp, i	3.2	3.4	3.6	3.8	4.0	4.2	4.4	4.6	4.8	5.0	5.2	5.4	5.6	5.8	6.0
2	-56
3	-43
4	-34	-46
5	-29	-36	-49
6	-26	-30	-39	—53
7	-21	-26	-31	-41	-58
8	-18	-22	-26	-32	-42
9	-16	-19	-22	-27	—33	-44
10	-13	-16	-19	-23	-27	—34	-45
11	-10	-13	-16	-19	-22	-27	-34	-46
12	- 8	-10	-13	-15	-19	-22	-27	-34	-47
13	- 6	g	—10	-12	-15	-18	-22	-27	-34	-46
14	- 4	- 6	- 8	-10	-12	-15	-18	-22	-27	-33	-45
15	- 2	- 4	— 5	— 7	- 9	-12	-15	-18	-21	-26	-32	-44
16	± 0	- 2	- 3	- 5	- 7	- 9	-11	-14	-17	-20	-25	-31	-42
17	1 0	±A	j		4	{*			10	T C	on	f>A	on	QO	K.T
18	•f- £» + 3	u + 2	+ 1	- 1	- 2	- 4	- 6	- 8	-10	-13	-16	-19	-23	-29	-37
19	+ 5	+ 4	+ 3	+ 1	± 0	- 2	- 4	- 5	_ fj	-10	-12	-15	-18	-22	-27
20	+ 7	+ 6	+ 4	-f 3	+ 2	± o	- 1	- 3	— 5	— 7	— 9	-11	-14	-17	-21

TABLE I. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 30.0 inches.

Air temp.	Vapor press.	Depression of wet-bulb thermometer (t — <').
t	e	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0	4.5	5.0	6.6	6.0	6.6	7.0	7.5
20	0.103	18	16	14	12	10	8	5	2	-2	-7	-13	-21	-37
21	.108	19	18	16	14	12	9	7	3	±0	—4	- 9	-16	-27	-60
22	.113	20	19	17	15	13	11	8	5	+2	-2	- 6	-12	-20	-36
	11 fl	91	20	18	16	14	12	10	1	4	+0	4	9	16	26	57
23 24	. llo .124	u 23	21	19	17	15	13	11	9	6	+2	- 1	- 6	-12	-20	—35
25	0.130	24	22	20	19	17	15	13	10	8	5	+ 1	- 3	- 8	-15	-25
26	.136	25	23	22	20	18	16	14	12	9	7	3	- 1	- 5	-11	-18
27	.143	26	24	23	21	19	18	16	13	11	8	5	+ 2	0	- 7	-14
28	.150	27	25	24	22	21	19	17	15	13	10	7	4	db 0	- 4	- 9
29	.157	28	26	25	23	22	20	18	16	14	12	9	6	+ 3	- 1	- 5
30	0.164	29	27	26	25	23	21	20	18	16	14	11	8	5	•f 2	- 2
31	.172	30	28	27	26	24	23	21	19	17	15	13	10	8	4	± o
32	.180	31	30	28	27	25	24	22	21	19	17	15	12	10	7	+ 3
33	.187	32	31	29	28	27	25	24	22	20	18	16	14	12	9	6
34	.195	33	32	30	29	28	26	25	23	22	20	18	16	13	11	8
35	0.203	34	33	31	30	29	28	26	25	23	81	19	17	15	13	10
36	.211	35	34	32	31	30	29	27	26	24	23	21	19	17	15	12
37	.219	36	35	33	32	31	30	28	27	26	24	22	21	19	17	14
38	.228	37	36	34	33	32	31	29	28	27	25	24	22	20	18	16
89	.237	38	37	35	34	33	32	31	29	28	27	25	23	22	20	18
40	0.247	39	38	37	35	34	33	32	30	29	28	26	25	23	21	20
41	.256	40	39	38	36	35	34	33	31	30	29	27	26	24	23	21
42	.266	41	40	39	38	36	35	34	33	31	30	29	27	26	24	23
43	.277	42	41	40	39	37	36	35	34	O.)	31	30	28	27	25	24
44	.287	43	42	41	40	38	37	36	35	34	32	31	30	28	27	25
45	0.298	44	43	42	41	40	38	37	36	35	34	32	n	30	28	27
46	.310	45	44	43	42	41	40	38	37	36	35	33	&	31	29	28
47	.322	46	45	44	43	42	41	40	38	37	36	35	33	32	31	29
48	.334	47	46	45	44	43	42	41	40	38	37	36	35	33	32	31
49	.347	48	47	46	45	44	43	42	41	40	38	37	36	34	33	32
50	0.360	49	48	47	46	45	44	43	42	41	40	38	37	36	34	33
61	.373	50	49	48	47	46	45	44	43	42	41	40	38	37	36	34
52	.387	51	60	49	48	47	46	45	44	43	42	41	40	38	37	36
53	.402	52	51	50	49	48	47	46	45	44	43	42	41	40	38	37
54	.417	53	52	51	50	49	48	47	46	45	44	43	42	41	40	38
55	0.432	54	53	52	51	50	50	49	48	47	45	44	43	42	41	' 40
56	.448	55	54	63	53	52	51	50	49	48	47	46	44	43	42	41
57	.465	56	55	64	54	53	52	51	50	49	48	47	46	45	43	42
58	.482	57	56	65	55	54	53	52	51	50	49	48	47	46	45	44
69	.499	58	57	56	56	55	54	53	52	51	50	49-	48	47	46	45
60	0.517	59	58	57	57	56	55	54	53	52	51	50	49	48	47	46
61	.536	60	59	59	58	57	56	55	54	53	52	51	50	49	48	47
62	.555	61	60	60	59	58	57	56	55	54	53	53	52	61	50	48
63	.575	62	61	61	60	59	58	57	56	55	55	54	53	52	51	50
64	.595	63	62	62	61	60	59	58	57	57	56	55	54	53	52	51
66	0.616	64	63	63	62	61	60	59	59	58	57	56	55	54	53	52
66	.638	65	64	64	63	62	61	60	60	59	58	67	56	55	54	53
67	.661	66	65	65	64	63	62	62	61	60	59	58	57	56	55	54
68	.684	67	67	66	65	64	63	63	62	61	60	59	58	57	57	56
69	.707	68	68	67	66	65	64	64	63	62	61	60	59	59	58	57
70	0.732	69	69	68	67	66	65	65	64	63	62	61	61	60	59	58
71	.757	70	70	69	68	67	67	66	65	64	63	62	62	61	60	59
72	.783	71	71	70	69	68	68	67	66	65	64	64	63	62	61	60
73	.810	72	72	71	70	69	69	68	67	66	66	65	64	63	62	61
74	.838	73	73	72	71	70	70	69	68	67	67	66	65	64	63	62
75	0 866	74	74	73	72	71	71	70	69	68	68	67	66	65	64	64
76	.896	75	75	74	73	72	72	71	70	69	69	68	67	66	66	66
77	.926	76	76	75	74	73	73	72	71	71	70	69	68	67	67	66
78	.957	77	77	76	75	75	74	73	72	72	71	70	69	69	68	67
79	0.989	78	78	77	76	76	75	74	73	73	72	71	70	70	69	68
80	1. 022	79	79	78	77	77	76	75	74	74	73	72	72	71	70	69

9181 °— li

TABLE I. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 30.0 inches.

Air temp. t	Vapor press. e	Depression of wet-bulb thermometer (t — <').
8.0	8.5	9.0	9.5	10.0	10.5	11.0	11.5	12.0	12.5	13.0'	13.5	14.0	14.5	15.0
25	0.130	-51
26	.136	-32
27	.143	-23	-45
28	.150	-17	-29
29	.157	-12	-20	-39
30	0.164	»T	-14	-25	-57
31	.172	- 4	-10	-18	-31
-—32	.180	- 1	- 6	-12	-21	-42
33	.187	4 2	- 2	- 7	-14	-26
34	.195	5	+ 1	- 3	- 9	-17	-32
35	0.203	7	4	± 0	- 5	-11	-20	-41
36	.211	10	7	+ 3	- 1	- 6	-14	-as	-58
37	.219	12	9	6	+ 2	- 3	- 8	-16	-29
38	.228	14	11	8	5	+ I-	— 4	-10	-19	-36
39^	.237	16	13	11	8	4	± 0	- 5	-12	-22	-47
— 40	\0. 247	18	15	13	10	7	+ 3	1	- 6	-14	-26
41	.256	19	17	15	12	10	6	+ 2	- 2	- 8	-16	-30
42	,266	21	19	17	14	12	9	6	+ 2	- 3	- 9	-18	-36
43	.277	'22	20	19	16	14	11	9	5	+ 1	- 4	-11	-21	-45
44	.287	24	22	20	18	16	13	11	8	4	+ 0	- 5	-12	-24	-CO
45	0.298	25	23	22	20	18	15	13	10	7	+ 4	- 1	- 6	-14	-27
46	.310	27	25	23	O1	20	17	15	13	10	7	+ 3	- 2	- 7	-16	-30
47	. 3'22	28	26	25	23	21	19	17	15	12	9	6	+ 2	— 3	- 9	-17
- 48	.334	29	28	26	25	23	21	19	17	14	12	9	5	+ 1	- 4	—10
49	.347	30	29	28	26	24	23	21	19	16	14	11	8	5	± c	- 5
50	0.360	32	30	29	27	26	24	22	21	18	16	13	11	8	+ 4	i fl
51	.373	33	32	30	29	27	26	24	22	20	18	16	13	10	7	+ 3
52	.387	34	33	32	30	29	27	26	24	22	20	18	16	13	10	7
53	.402	36	34	89	32	30	29	27	26	24	22	20	18	15	13	10
54	.417	37	36	34	33	3'2	30	29	27	25	24	22	20	18	15	12
55	0. 432	38	37	36	34	33	32	30	29	27	25	24	22	20	17	15
— 56	.448	40	39	37	36	34	33	32	30	29	27	25	24	22	19	17
57	.465	41	40	39	37	36	34	33	32	30	29	27	25	24	21	19
58	.482	42	41	40	39	37	36	35	33	32	30	29	27	25	23	21
59	.499	44	43	41	40	39	37	36	35	33	32	30	29	27	25	23
CO	0.5ft	45	44	43	41	40	39	38	36	35	33	32	30	29	27	25
61	.536	46	45	44	43	42	40	39	38	36	35	33	32	30	29	27
62	.555	47	46	45	44	43	42	40	3&	38	36	35	33	32	30	29
63	.575	49	48	47	45	44	43	42	41	39	38	36	35	34	32	30
— 64	.595	50	49	48	47	40	44	43	42	41	39	38	37	35	34	32
65	0.616	51	50	49	48	47	46	45	43	42	41	40	38	37	35	34
66	.638	52	51	50	49	48	47	46	45	44	42	41	40	38	37	35
67	.661	53	53	52	60	49	48	47	46	45	44	43	41	40	38	37
68	.684	55	54	53	52	51	50	49	48	46	45	44	43	42	40	39
69	.707	56	55	54	53	52	51	50	49 '	48	46	45	44	43	42	40
70	0.732	57	56	55	54	53	52	51	50	49	48	47	46	44	43	42
71	.757	58	57	56	55	54	53	52	51	50	49	48	47	46	45	43
— 72	.783	59	58	58	57	56	55	54	53	52	51	50	48	47	46	45
73	.810	60	60	59	58	57	5(5	55	54	53	52	51	50	49	48	46
74	.838	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48
.75	0.866	63	62	Gl	60	59	58	57	56	55	55	54	52	51	50	49
76	.896	64	63	62	61	60	60	59	58	57	56	55	54	53	52	51
77	.926	65	64	63	62	62	61	60	59	58	57	56	55	54	53	52
78	.957	66	65	64	64	03	62	61	60	59	58	57	56	55	54	53
79	0.989	67	66	66	65	64	63	62	61	60	59	59	58	57	5G	55
— 80	1.022	68	68	67	66	65	64	63	63	62	61	60	59	58	57	56

19

TABLE I. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 30.0 inches.

Air	Depression of wet-bulb thermometer (I— I').
tcrop.	15.5	16.0	16.5	17 0	17.5	18.0	18.5	19.0	19.5	20.0	20.5	21.0	21.5	91 0	22.5
47	—35
48	-'20	-41
49	-12	-22	-53
50	- 6	-13	-26
51	- 1	- 7	-15	-29
52	+ 3	- 2	- 8	—17	—33
53	7	+ 2	- 3	- 9	-18	-39
54	10	(\	+ 2	- 4	-10	-20	-47
65	12	9	6	+ 1	- 4	-12	-23	-59
56	15	12	9	5	+ 1	- 5	— 13	-25
57	17	14	12	9	5	± 0	- 6	-14	-27
58	19	17	14	11	8	+ 4	- 1	— 6	—15	-30
59	21	19	17	1-1	11	8	+ 4	- 1	- 7	--16	-33
60	23	21	19	17	14	11	8	+ 4	- 2	-— 8	-17	-36
61	25	23	21	19	17	14	11	8	+ 3	n	- 8	-18	-40
62	27	25	23	21	19	16	14	11	7	-*• 3	- 2	- 9	-19 -45
63	29	27	25	23	21	19	17	14	11	7	+ 3	- 2	- 9 -20	-49
64	31	29	27	25	23	21	19	17	14	11	7	+ 3	- 3 -10	-21
65	32	31	29	27	25	24	21	19	17	14	11	7	+ 3	- 3	-10
66	34	32	31	29	27	26	24	22	19	17	14	11	7	+ 2	- 3
67	36	34	32	31	29	28	26	24	22	19	17	14	11	7	+ 2
68	37	36	34	33	31	29	28	26	24	22	19	17	14	11	7
69	39	37	36	34	33	31	30	28	26	24	22	19	17	14	11
70	40	39	38	36	34	33	31	30	28	26	24	22	20	17	14
71	42	41	39	38	36	35	33	31	30	28	26	24	22	20	17
72	44	42	41	40	38	37	35	33	32	30	28	26	24	22	20
73	45	44	43	41	40	38	. 37	35	34	32	30	28	27	25	22
74	47	45	44	$	41	40	39	37	35	34	32	30	29	27	25
75	48	47	46	44	43	42	40	39	37	36	34	32	31	29	27
76	49	48	47	46	45	43	42	41	39	38	36	34	33	31	29
77	51	50	49	18	46	45	44	42	41	39	38	36	35	33	31
78	52	51	50	19	48	46	45	44	43	41	40	38	37	35	33
79	54	53	52	50	-19	48	47	46	44	43	42	40	38	37	35
80	55	54	53	52	51	50	48	47	46	44	43	42	40	39	37
	Depression of wet-bulb thermometer (<—£').
	23.0	23.5	24.0	24.5	25.0	25.5	26.0	26.5	27.0	27.5	28.0	28.5	29.0	29.5	30.0
64	-54
65	-22
66	-11	-22
67	- 3	-11	-23
68	+ 2	— 3	-11	-24
69	7	+ 2	t o	-11	^)A
70	11	7	+ 2	- 3	-11	-24
71	14	11	7	+ 3	- 3	-11	-24
72	17	14	11	7	+ 3	- 3	—11	-24
73	20	17	15	11	8	+ 3	- 3	-11	-24
74	23	20	18	15	12	8	+ 3	- 3	-10	-24
75	25	23	21	18	15	12	8	+ 4	- 2	-10	-23
76	27	25	23	21	18	15	12	8	+ 4	- 2	—10	22
77	29	28	26	23	21	18	16	13	9	+ 4	- 2	- 9	-21
78	31	30	28	26	24	21	19	16	13	9	+ 6	- 1	— 9	-20
79	34	32	30	28	26	24	22	19	16	13	10	+ 5	- 1	— 8	-20
80	36	34	32	30	28	26	24	22	20	17	13	10	+ 6	± 0	- 7

TABLE I.— Temperature of dew-point in degrees Fahrenheit.

Pressure=30.0 inches.

Air temp.	Vapor press.	Depression of wet-bulb thermometer (t — <').
t	e	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
80	1.022	79	77	76	74	73	72	70	68	67	65	63	62	60	58	56
81	.056	80	78	77	75	74	73	71	70	68	66	65	63	61	59	57
82	.091	81	79	78	77	75	74	72	71	69	67	66	64	62	60	59
83	.127	82	80	79	78	76	75	73	72	70	69	67	65	64	62	60
84	.163	83	81	80	79	77	76	74	73	71	70	68	66	65	63	61
85	1.201	84	82	81	80	78	77	75	74	72	71	69	68	66	64	62
86	.241	85	83	82	81	79	78	76	75	73	72	70	69	67	65	64r
87	.281	86	84	83	82	80	79	78	76	75	73	72	70	68	67	65
— 88	.322	87	85	84	83	81	80	79	77	76	74	73	71	69	68	66
89	.364	88	86	85	84	82	81	80	78	77	75	74	72	71	69	67
90	1.408	89	87	86	85	83	82	81	79	78	76	75	73	72	70	69
91	.453	90	88	87	86	85	83	82	80	79	78	76	75	73	71	70
92	.499	91	89	88	87	86	84	83	81	80	79	77	76	74	73	71
93	.546	92	90	89	88	87	85	84	83	81	80	78	77	75	74	72
94	.595	93	92	90	89	88	86	85	84	82	81	79	78	76	75	73
95	1.645	94	93	91	90	89	87	86	85	83	82	80	79	78	76	74
— 96	.696	95	94	92	91	90	88	87	86	84	83	82	80	79	77	76
97	.749	96	95	93	92	91	89	88	87	85	84	83	81	80	78	77
98	.803	97	96	94	93	92	90	89	88	87	85	84	82	81	79	78
99	.859	98	97	95	94	93	92	90	89	88	86	85	83	82	81	79
100	1.916	99	98	96	95	94	93	91	90	89	87	86	85	83	82	80
101	1.975	100	99	97	96	95	94	92	91	90	88	87	86	84	83	81
102	2.035	101	100	98	97	96	95	93	92	91	89	88	87	85	84	83
103	.097	102	101	99	98	97	96	94	93	92	91	89	88	86	85	84
104	.160	103	102	IOC	99	98	97	95	94	93	92	90	89	88	86	85
105	2.225	104	103	101	100	99	- 98	96	95	94	93	91	90	89	87	86
106	.292	105	104	102	101	100	99	. 98	96	95	94	92	91	90	88	87
107	.360	106	105	103	102	101	100	99	97	96	95	93	92	91	90	88
108	.431	107	106	104	103	102	101	100	98	97	96	95	93	92	91	89
109	.503	108	107	105	104	103	102	101	99	98	97	96	94	93	92	90
110	2.576	109	108	106	105	104	103	102	100	99	98	97	95	94	93	91
111	.652	110	109	108	106	105	104	103	102	100	99	98	96	95	94	93
112	. 730	lit	110	109	107	106	105	104	103	101	100	99	98	96	95	94
113	.810	112	111	110	108	107	106	105	104	102	101	100	99	97	96	95
114	.891	113	112	111	109	108	107	106	105	103	102	101	100	98	97	96
115	2.975	114	113	112	110	109	108	107	106	104	103	102	101	99	98	97
116	3.061	115	114	113	111	110	109	108	107	105	104	103	102	101	99	98
117	.148	116	115	114	112	111	110	109	108	107	105	104	103	102	100	99
118	.239	117	116	115	113	112	111	110	109	108	106	105	104	103	101	100
119	.331	118	117	116	114	113	112	111	110	109	107	106	105	104	102	101
120	3.425	119	118	117	115	114	113	112	111	110	108	107	106	105	104	102
121	.522	120	119	118	116	115	114	113	112	111	109	108	107	106	10.-)	103
122	.621	121	120	119	118	116	115	114	113	112	110	109	108	107	106	104
123	.723	122	121	120	119	117	116	115	114	113	112	110	109	108	107	106
124	.827	123	122	121	120	118	117	116	115	114	113	111	110	109	108	107
125	3.933	124	123	122	121	119	118	117	116	115	114	112	111	no	109	108
126	4.042	125	124	123	122	120	119	118	117	116	115	113	112	in	110	109
127	.154	126	125	124	123	121	120	119	118	117	116	114	113	112	111	110
128	.268	127	126	125	124	122	121	120	119	118	117	116	114	113	112	111
129	.385	128	127	126	125	123	122	121	120	119	118	117	115	114	113	112
130	4.504	129	128	127	126	124	123	122	121	120	119	118	116	115	114	113
131	.627	130	129	128	127	125	124	123	122	121	120	119	117	116	115	114
132	.752	131	130	129	128	126	125	124	123	122	121	120	119	117	116	115
133	4.880	132	131	130	129	1-27	126	125	124	123	122	121	120	118	117	116
134	5.011	133	132	131	130	129	127	126	125	124	123	122	121	119	118	117
135	5. 145	134	133	132	131	130	128	127	126	125	124	123	122	120	119	118
136	.282	135	134	133	132	131	129	128	127	126	125	124	123	122	120	119
137	.422	136	135	134	133	if*	130	129	128	127	126	125	124	123	121	120
138	.566	137	136	135	134	133	131	130	129	128	127	126	125	124	122	121
139	.712	138	137	136	135	134	132	131	130	129	128	127	126	125	123	132
140	5.862	139	138	137	136	135	133	132	131	130	129	128	»	126	124	123

21

TABLE I. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 30.0 inches.

Air temp. I	Vapor press. e	Depression of wet-bulb thermometer (t — tf).
16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
80	1.022	54	52	50	47	44	42	39	36	32	28	24	20	13	6	-7
81	.056	55	53	51	49	46	43	41	38	34	31	27	22	17	10	±0
82	.091	57	55	52	50	48	45	42	39	36	33	29	25	20	14	+7
83	.127	58	56	54	52	49	47	44	41	38	35	31	27	23	18	11
84	.163	59	57	55	53	61	48	46	43	40	37	34	30	26	21	15
85	1.201	61	59	57	54	52	50	48	45	42	39	36	32	28	24	19
86	.241	62	60	58	56	54	52	49	47	44	41	38	34	31	27	22
87	.281	63	61	59	57	55	53	51	48	46	43	40	36	33	29	25
88	.322	64	62	61	59	57	55	52	50	47	45	42	38	35	31	27
89	.364	66	64	62	60	58	56	54	51	49	46	44	41	37	34	30
90	1.408	67	65	63	61	59	57	55	53	51	48	45	43	39	36	32
91	.453	68	66	65	63	61	59	57	55	62	50	47	44	41	38	35
92	.49!)	69	68	66	64	62	60	58	56	54	51	49	46	43	40	37
93	.546	71	69	67	65	63	62	60	58	55	53	61	48	45	42	39
94	.596	72	70	68	67	65	63	61	59	57	55	52	50	47	44	41
95	1.645	73	71	70	68	66	64	62	60	58	56	FA	52	49	46	43
96	.696	74	72	71	69	67	66	64	62	60	58	55	53	51	48	46
J7	.749	75	74	72	70	69	67	65	63	61	59	57	55	52	60	47
98	.803	76	75	73	72	70	68	66	64	63	61	58	56	54	62	49
99	.859	78	76	74	73	71	69	68	66	64	62	60	58	56	63	51
100	1.916	79	77	76	74	72	71	69	67	65	63	61	59	67	55	52
101	1.975	80	78	77	75	74	72	70	69	67	65	63	61	59	66	54
102	2.035	81	80	78	76	75	73	72	70	68	66	64	62	60	68 1 56
103	.097	82	81	79	78	76	74	73	71	69	68	66	64	62	60 57
104	.160	83	82	80	79	77	76	74	72	7.1	69	67	65	63	61 59
105	2. 225	84	83	82	80	78	77	75	74	72	70	68	67	65	63 61
106	.292	86	84	83	81	80	78	77	75	73	72	70	68	66	64	62
107	.360	87	85	84	82	81	79	78	76	75	73	71	69	67	66	64
108	.431	88	86	85	84	82	81	79	77	76	74	72	71	69	67	65
109	.503	89	88	86	85	83	82	80	79	77	75	74	72	70	68	66
110	2.576	90	89	87	86	84	83	81	80	78	77	75	73	72	70	68
111	.652	91	90	88	87	86	84	83	81	80	78	76	75	73	71	69
112	.730	92	91	90	88	87	85	84	82	81	79	78	76	74	72	71
113	.810	93	92	91	89	88	86	85	84	82	80	79	77	76	74	72
114	.891	94	93	92	90	89	88	86	85	83	82	80	79	77	75	73
115	2.975	96	94	93	92	90	89	87	86	84	83	81	80	78	76	75
116	3.061	97	95	94	93	91	90	88	87	86	84	83	81	79	78	76
117	.148	98	96	95	94	92	91	90	88	87	85	84	82	81	79	77
118	.239	99	98	96	95	94	92	91	89	88	86	85	84	82	80	79
119	.331	100	99	97	96	95	9r	92	91	89	88	86	85	83	82	80
120	3.425	101	100	98	97	96	94	93	92	90	89	87	86	84	83	81
121	.522	102	101	100	98	97	96	94	93	91	90	89	87	86	84	83
122	.621	103	102	101	99	98	97	95	94	93	91	90	88	87	85	84
123	.723	1U4	103	102	100	99	98	96	95	94	92	91	90	88	87	85
124	.827	105	104	103	102	100	99	98	96	95	94	92	91	89	88	86
125	3. 933	106	105	104	103	101	100	99	97	96	95	93	92	90	89	88
126	4. 0*2	107	106	105	104	102	101	100	99	97	96	94	93	92	90	89
127	.lot	109	107	106	105	104	102	101	100	98	97	96	94	93	91	90
128	.268	110	108	107	106	105	103	102	101	99	98	97	95	94	93	91
129	. 385	111	109	108	107	106	104	103	102	101	99	98	97	95	94	92
130	4.504	112	110	109	108	107	106	104	103	102	100	99	98	96	95	94
131	.627	113	112	110	109	108	107	105	104	103	101	100	99	97	96	95
132	.752	114	113	111	110	109	108	106	105	104	103	101	100	99	97	96
133	.880	115	114	112	111	110	109	108	106	105	104	102	101	100	98	97
134	5.011	116	115	114	112	111	110	109	107	106	105	104	102	101	100	98
135	5.145	117	116	115	113	112	111	110	108	107	106	105	103	102	101	99
136	.282	118	117	116	114	113	112	111	110	108	107	106	104	103	102	101
137	.422	119	118	117	116	114	113	112	111	109	108	107	106	104	103	102
138	.565	120	119	118	117	115	114	113	112	110	109	108	107	105	104	102
139	.712	121	120	119	118	116	115	114	113	112	110	109	108	107	105	104
140	5.862	122	121	120	119	117	116	115	114	113	111	110	109	108	106	105

22

TABLE I. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 30. 0 inches.

Air temp.	Vapor press.	Depression of wet-bulb thermometer (t--f).
t	t	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45
80	1.022	-53
81	.056	-18
82	.091	- 6	—43
83	.127	+ 2	-15
84	.163	8	- 4	-33
85	1.201	12	+ 3	-12
86	.241	16	9	- 2	-27
87	.281	20	13	+ 5	-10
88	.322	23	17	10	4- 0	-22
89	.364	26	21	15	+ 6	- 7
90	1.408	28	24	19	11	+ 1	-17
91	.453	31	27	22	16	8	— 4	-40
92	.499	33	29	25	20	13	+ 4	-13
93	.546	36	32	28	23	17	10	- 2	-28
94	.595	38	34	30	26	21	14	+ 6	— 9
95	1.645	40	37	33	29	24	19	11	+ 1	-20
96	.696	42	39	35	31	27	22	16	8	- 5
97	.749	44	41	38	34	30	25	20	13	+ 3	-15
98	.803	46	43	40	36	32	28	23	17	10	- 2	-33
99	.859	48	45	42	39	35	31	26	21	15	+ 6	-10
100	1.916	50	47	44	41	37	33	29	25	19	12	+ 1	-22
101	1.975	52	49	46	43	40	36	32	28	23	17	8	- 5
102	2. 035	53	51	48	45	42	38	35	31	26	21	14	+ 4	-14
103	.097	55	53	50	47	44	41	37	33	29	24	18	11	- 2	-32
104	.160	57	54	52	49	46	43	40	36	32	27	22	16	+ 7	- 9
105	2.225	58	56	54	51	48	45	42	38	34	30	26	20	13	+ 2	-2G
106	.292	60	58	55	53	50	47	44	41	37	33	29	24	18	9	- 4
107	.360	62	59	57	55	52	49	46	43	40	36	32	27	22	15	+ 5
108	.431	63	61	59	56	54	51	48	45	42	39	35	30	25	20	12
109	.503	64	62	60	58	56	53	50	47	44	41	37	33	29	23	17
110	2.576	66	64	62	60	57	55	52	50	47	43	40	36	32	27	21
111	.652	67	65	63	61	59	57	54	52	49	46	42	39	35	30	25
112	.730	69	67	65	63	61	58	56	54	51	48	45	41	37	33	29
113	.810	70	68	66	64	62	60	58	55	53	50	47	44	40	36	32
114	.891	72	70	68	66	64	62	59	57	55	52	49	46	43	39	35
115	2.975	73	71	69	67	65	63	61	59	56	54	51	48	45	42	38
116	3. 061	74	73	71	69	67	65	63	60	58	56	53	50	47	44	40
117	.148	76	74	72	70	68	66	64	62	60	58	55	52	49	46	43
118	. 239	77	75	74	72	70	68	66	64	62	59	57	54	51	49	45
119	.331	78	77	75	73	71	69	67	65	63	61	59	56	53	51	48
120	3.425	80	78	76	75	73	71	69	67	65	63	60	58	55	53	50
121	.522	81	79	78	76	74	72	70	68	66	64	62	60	57	55	52
122	.621	82	81	7'J	77	76	74	72	70	68	66	64	62	59	57	54
123	.723	84	82	80	79	77	75	73	71	69	67	65	63	61	58	56
124	.827	85	83	82	80	78	77	75	73	71	69	67	65	63	60	58
125	3.933	86	84	83	81	80	78	76	74	72	71	69	66	64	62	60
126	4.042	87	86	84	83	81	79	78	76	74	72	70	68	66	64	62
127	.154	88	87	85	84	82	81	79	77	75	74	72	70	68	65	63
128	.268	90	88	87	85	84	82	80	79	77	75	73	71	69	67	65
129	.385	91	89	88	86	85	83	82	80	78	76	75	73	71	69	67
130	4.504	92	91	89	88	86	85	83	81	80	78	76	74	72	70	68
131	.627	93	92	90	89	87	86	84	83	81	79	77	76	74	72	70
132	.752	94	93	92	90	89	87	86	84	82	81	79	77	75	73	71
133	.880	96	94	93	91	90	88	87	85	84	82	80	78	77	75	73
134	5.011	97	95	94	93	91	90	88	87	85	83	82	80	78	76	74
135	5.145	98	97	95	94	92	81	89	88	86	85	83	81	80	78	76
136	.282	99	98	96	95	94	92	91	89	88	86	84	83	81	79	77
137	.422	100	99	98	96	95	93	92	90	89	87	86	84	82	81	79
138	.565	101	100	99	97	96	95	93	92	90	89	87	85	84	82	80
139	.712	10:}	101	100	99	97	96	94	93	hi	90	88	87	85	83	82
140	5.862	104	102	101	100	98	97	96	94	93	91	90	88	86	85	83

TABLE I. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 30.0 inches.

Air temp. t	Depression of wet-bulb thermometer (t — t').
46	47	48	49	50	51	52	53	54	55	56	57	58	59	60
106	—56
107	—12
108	± 0	-26
109	+ 8	— 6
110	14	+ 4	—16
111	19	11	- 1	-35
112	23	17	+ 8	- 8
113	27	21	14	+ 3	—19
114	30	25	19	11	- 2	-50
115	33	29	23	16	+ 7	-10
116	36	32	27	21	14	+ 2	-22
117	39	35	30	25	19	10	- 3
118	42	38	34	29	23	16	+ 7	-11
119	44	41	37	32	27	21	14	+ 2	—25
120	47	43	39	35	30	25	19	10	— 4
121	49	46	42	38	34	29	23	16	+ 6	-12
122	51	48	45	41	37	32	27	21	14	+ 1	-27
123	53	50	47	44	40	36	31	25	19	10	- 4
124	55	52	49	46	43	39	34	29	24	17	+ 7	— 13
125	57	54	52	49	45	42	37	33	28	2'2	14	+ 2	-29
126	59	56	54	51	48	44	40	36	31	26	19	11	— 4
127	61	58	56	53	50	47	43	39	35	30	24	17	+ 7	-13
128	63	60	58	55	52	49	46	42	38	33	28	22	14	+ 2	-2T
129	64	62	60	57	54	51	48	45	41	37	32	26	20	11	- 4
130	66	64	62	59	56	54	51	47	44	40	35	30	25	17	+ 7
131	68	66	• 63	61	58	56	53	50	46	43	39	34	29	23	15
132	69	67	65	63	60	58	55	52	49	45	42	37	32	27	21
133	71	69	67	64	62	60	57	54	51	48	44	40	36	31	25
134	73	71	68	66	64	62	59	56	53	50	47	43	39	34	29
135	74	72	70	68	66	88	61	58	56	53	50	46	42	38	33
136 137	76 77	I	72 73	70 71	67 69	65 07	63 65	60 62	58 60	55 57	52 54	49 51	45 48	41 44	37 40
138	78	77	75	73	71	<}<.)	66	64	62	59	56	53	50	47	43
139	80	78	76	74	72	70	68	66	64	61	58	56	53	60	46
140	81	80	78	76	74	72	70	68	65	63	GO	58	55	52	4&

DEW-POINT

24

TABLE II. — Temperature of dew-point in degrees Fahrenheit.

Pressure=»=29.0 inches.

Air	Vapor	Depression of wet-bulb thermometer (t — </).
t	e	.2	.4	.6	.8	1.0 1.2	1.4	1.6	l.fi	2.0 2.2	2.4	2.6	2.8	3.0
—40 -39 .g{	.0039 41 44	—61 -50 49				r	1				tM
-37	46	-47						€	'	€	.1	.2	.3	.4	.5
—36	48	—46
—36	.0051	—44					—60	.0010	-50	.0021	—60
-34	54	-43	—58				-59	11	-49	22	-58
—33	57	—41	—55				—58	12	-48	24	-56
—32	61	-40	-52				-57	13	-47	26	-55
-31	65	-38	-49				-56	13	—46	27	-53
-30	.0069	—36	—47				-55	.0015	—45	. 0029	-51
-29	74	-34	-44				—54	16	-44	31	-50	-59
-28	78	—33	-42	-56			-53	17	-43	33	—49	-57
-27	83	-32	-40	-52			-52	18	-42	35	-48	-55
-26	89	-30	-37	-49			-51	19	-41	37	-46	—53
-25 —24	.0094 .0100	-29 -28	-35 —34	-45 -42	-57		-39	.0039 41	—45 -44	-50	-60
-23	106	-27	-32	-40	-51		-38	44	-43	-49	-58
-22	112	-26	-30	-37	-47		-37	46	-42	-47	-55
-21	119	-24	-29	-34	-44	-60				-36	48	-41	-46	-53
—20	.0126	-23	—28	-33	—40	—53				-35	.0051	-40	-44	-51
- 19	133	-22	-26	-31	-37	-48				-34	54	-38	-43	-49	-58
-18	141	- 21	—25	-29	—34	—44				—33	57	-37	-41	-47	-55
-17	150	--20	--23	-27	-32	-40	-55			-32	61	-35	-40	-45	-52
—16	159	-18	-22	-26	-30	-37	--48			—31	65	-34	-38	-43	-49	-58
-15	.0168	-17	-20	-24	28	-34	-43	-59		-30	.0069	-33	-36	-41	-47	-54
-14	178	-16	-19	-22	-26	-31	-39	-51
-13 —12	188 199	-15 -14	-18 -17	-21 -19	-24 -23	-29 -27	-35 -32	-45 -40	-63
—11	210	-13	-15	-18	-21	-25	-29	-36	-46
-10	.0222	-12	-14	-17	-19	-23	-27	-32	-40	-56
- 9	234	-11	—13	-15	-18	-21	-25	-29	-36	-47
~ 8	247	-10	-12	-14	-16	-19	-23	-27	-32	-41	-55
- 7	260	- 9	-11	-13	-15	-18	-21	-24	-29	-35	-46
- 6	275	- 8	-10	-12	-14	-16	-19	-22	-20	-32	-40	-54
— 5	.0291	- 7	- 8	-10	-12	-15	-17	-20	-24	-29	-35	-45
— 4	307	- 5	- 7	- 9	-11	—13	-16	-18	-22	-26	-30	-38	—50
- 3	325	- 4	- 6	- 8	^-10	-12	-14	-16	-19	-23	-27	-32	-42	-59
- 2	344	- 3	- 5	- 6	- 8	--10	-12	—15	-17	-20	-24	-29	-35	-47
- 1	363	2	- 4	- 5	t fj	- 9	-11	-13	-15	-18	- 21	-25	-30	-38	-51
0	.0383	- 1	- 3	- 4	- 5	- 7	— 9	-11	-13	-16	-19	-22	-26	-32	-40	-57
"HI	403	± 0	- 2	- 3	— 4	— 6	- 7	— 9	-12	-14	-16	-19	-23	-28	-34 -44
2	423	+ 1	± 0	- 2	- 3	- 5	— 6	- 8	-10	-12	-14	- 17	-20	-24	-29 -35
3	444	2	+ 1	- 1	- 2	- 3	- 5	- 6	- 8	—10	-12	-15	-18	21	—25	-30
4	467	3	2	± 0	1	- 2	- 4	— 5	- 7	- 9	-11	—13	-15	-18	-22	-26
5	.0491	4	3	+ 2	± 0	- 1	— 2	- 4	- 5	- 7	- 9	-11	13	16	-19	-22
6	515	5	4	3	+ 1	db 0	- 1	- 2	- 4	- 5	- 7	- 9	-11	-14	—16 -19
7	542	6	5	4	3	+ 1	± 0	- 1	— 3	- 4	5	- 7	- 9	-12	-14 -16
8	570	7	6	5	4	3	+ 1	± 0	- 1	- 3	— 4	— 5	- 7	-10	-12 -14
9	600	8	7	6	5	4	3	+ 1	i 0	1	3 1	— 4	g	g
10	.0631	9	8	7	6	5	4	3	4- 1	± 0
11	665	10	9	8	7	6	5	4	1" A 3	+ 2	± 0	- 1	- 2	— 4	— 6 — 7
12	699	11	10	9	9	8	7	6	4	3	+ 2	-4- 1	— 1	— 2	— 4 — 5
13	735	12	11	11	10	9	8	7	6	5	3	2	+ 1	— l	— 2 — 4
14	772	13	12	12	11	10	9	8	7	6	5	4	3	+ 1	± 0 - 2
15	.0810	14	13	13	12	11	10	9	8	7	6	5	4	3	+ 1 I -*- 0
16	850	15	15	14	13	12	11	10	9	9	8	7	6	4	31-4-2
17	891	16	16	15	14	13	12	12	11	10	9	8	7	6	5	4
18	933	17	17	16	15	14	14	13	12	11	10	9	8	7	0	5
19	.0979	18	18	17	16	15	15	14	13	12	11	11	10	9	8	7
20	.1026	19	19	18	17	17	16	15	14	13	13	12	11	10	9	8

TABLE II. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 29.0 inches.

Air temp. t	Depression of wet-bulb thermometer (t—f).
3.2	3 4	3.6	3.8	4.0	4.2	4.4	4.6	4.8	5.0	5.2	5.4	5.6	f> 8	6.0
2
-47
3	-37	—50
4	-31	-40	-55
5	-27	-32	-42	-59
6	-23	-28	-34	-44
7	-20	-24	-28	-35	-47
8	-17	-20	-24	-'29	-36	-49
9	-14	-17	-20	-24	-29	-37	-50
10	-12	-14	-17	-20	-25	-30	-37	-52
11	y	-12	-14	—17	-20	-25	— 3'»	—38	—53
12	- 7	Q	-11	-14	-17	-20	-24	-30	-38	-52
13	- 5	7	- 9	— 11	-14	-17	-20	24	—29	-37	51
14	- 3	- 5	- 7	- 9	-11	-13	--16	-19	-24	-29	-36	-49
15	-1	— 3	- 4	— 6	- 8	-10	-13	-16	— 19	-23	-28	-35	-48
16	4- 0	- 1	0	— 4	— 6	- 8	-10	-12	-15	-18	-22	-27	-33	-45
17	+ 2	+ 1	± 0	- 2	A	- 5	— 7	- 9	—12	-14	-17	-21	—26	-32	-42
18	4	8	+ l	4- 0	- 2	3	- 5	- 7	— <»	-11	-14	-17	-20	-24	-30
19	6	4	3	+ 2	± 0	- i	— 3	- 4	— 6	— 8	-10	-13	-16	-19	—23
20	7	6	5	4	+ 2	+ i	r 1	— 2	— 4	- 5	- 7	-10	-12	-15	-18

DEW-POINT

26

TABLE II. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 29.0 inches.

Air temp	Vapor press.	Depression of wet-bulb thermometer (t—f).
t	e	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0	4.5	5.0	5.5	6.0	6.5	7.0	7.5	8.0
20	0.103	18	17	15	13	11	8	5	2	-1	-5	-11	-18	-30
21	.108	19	18	16	14	12	10	7	4	+1	—3	- 8	-14	-23	-42
22	.113	20	19	17	15	13	11	9	6	3	-1	- 5	-10	-17	-29
23	.118	22	20	18	16	14	12	10	8	5	+1	- 3	- 7	-13	-22	-40
24	.124	23	21	19	18	16	14	11	9	6	3	± 0	- 4	-10	-17	-28
25	0.130	24	22	21	19	17	15	13	11	8	5	+ 2	- 2	- 6	-12	-21	• 36
26	.136	25	23	22	20	18	16	14	12	10	7	4	± 0	- 4	- 9	-15	-26
27	.143	26	24	23	21	20	18	16	14	12	9	6	+ 3	- 1	- 5	-11	-19
28	.150	27	25	24	22	21	19	17	15	13	11	8	5	+ 2	- 2	— 7	-14
29	.157	28	26	25	24	22	20	19	17	15	12	10	7	4	± 0	- 4	g
30	0.164	29	27	26	25	23	22	20	18	16	14	12	9	6	+ 3	- 1	- 5
31	.172	30	29	27	26	24	23	21	20	18	16	13	11	8	5	+ 2	- 2
32	.180	31	30	28	27	26	24	23	21	19	17	15	13	10	8	4	+ 1
33	.187	32	31	29	28	27	25	24	22	21	19	17	15	12	10	7	3
34	.195	33	32	30	29	28	27	25	24	22	20	18	16	14	12	9	6
35	0.203	34	33	31	30	29	28	26	25	23	22	20	18	16	14	11	8
36	.211	35	34	32	31	30	29	27	26	25	23	21	20	18	15	13	11
37	.219	36	35	33	32	31	30	28	27	26	24	23	21	19	17	15	13
38	.228	37	36	34	33	32	31	30	28	27	26	24	23	21	19	17	14
39	.237	38	37	36	34	33	32	31	29	28	27	25	24	22	21	19	16
40	0.247	39	38	37	35	34	33	32	31	29	28	27	25	23	22	20	18
41	.256	40	39	38	37	35	34	33	32	30	29	28	26	25	23		20
42	.266	41	40	39	38	36	35	34	33	32	30	29	28	26	25	23	21
43	.277	42	41	40	39	38	36	35	34	33	31	30	29	27	26	24	23
44	.287	43	42	41	40	39	38	36	35	34	32	31	30	29	27	26	24
45	0.298	44	43	42	41	40	39	37	36	35	•34	32	31	30	29	27	26
46	.310	45	44	43	42	41	40	39	37	36	35	34	32	31	30	28	27
47	..322	46	45	44	43	42	41	40	39	37	36	35	34	32	31	30	28
48	.334	47	46	45	44	43	42	41	40	39	37	36	35	34	32	31	30
49	.347	48	47	46	45	44	43	42	41	40	39	37	36	35	34	32	31
50	0.360	49	48	47	46	45	44	43	42	41	40	39	37	36	35	34	32
51	.373	50	49	48	47	46	45	44	43	42	41	40	39	37	36	35	34
52	.387	51	50	49	48	47	46	45	44	43	42	41	40	39	37	36	35
53	.402	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	36
54	.417	63	52	51	50	49	49	48	47	46	44	43	42	41	40	39	38
65	0.432	54	53	52	52	51	50	49	48	47	46	45	4:5	42	41	40	39
66	.448	55	54	53	53	52	51	50	49	48	47	46	45	44	43	41	40
67	.465	56	55	54	54	53	52	51	50	49	48	47	46	45	44	43	42
58	.482	57	56	56	55	54	53	52	51	50	49	48	47	46	45	44	43
59	.499	68	57	57	56	55	54	53	52	51	50	49	48	47	46	45	44
60	0.517	59	58	58	57	56	55	54	53	52	51	50	49	48	47	46	45
61	.536	60	59	59	58	57	56	55	54	53	52	52	51	50	49	48	46
62	.555	61	60	60	59	58	57	56	55	55	54	53	52	51	50	49	48
63	.575	62	61	61	60	59	58	57	56	56	55	54	53	52	51	50	49
64	.595	63	62	62	61	60	59	58	58	57	56	55	54	53	52	61	50
65	0.616	64	63	63	62	61	60	59	59	58	57	56	55	54	53	52	51
66	.638	65	64	64	63	62	61	61	60	59	58	57	56	55	54	54	53
67	.661	66	65	65	64	63	62	62	61	60	59	58	57	56	56	55	54
68	.684	67	67	66	65	64	63	63	62	61	60	69	58	68	57	56	55
69	.707	68	68	67	66	65	64	64	63	62	61	60	60	69	58	57	56
70 71	0.732 .757	69 70	69 70	68 69	67 68	66 67	66 67	65 66	64 65	63 64	62 63	62 63	61 62	60 61	59 60	58 59	57 58
72	.783	71	71	70	69	68	68	67	66	65	65	64	63	62	61	60	60
73	.810	72	72	71	70	69	69	68	67	66	66	65	64	63	62	62	61
74	.838	73	73	72	71	70	70	69	68	67	67	66	65	64	64	63	62
75 76 77 78 79	0.866 .896 .926 .957 0.989	74 75 76 77 78	74 75 76 77 78	73 74 75 '76 77	72 73 74 75 76	71 73 74 75 76	71 72 73 74 75	70 71 72 73 74	69 70 71 72 73	68 70 71 72 73	68 69 70 71 72	67 68 69 70 71	66 67 68 69 70	65 66 68 69 70	65 66 67 68 69	64 65 66 67 68	63 64 65 66 67
80	1.022	79	79	78	77	77	76	75	75	74	73	72	72	71	70	69	69

DEW-POINT

27

TABLE II. — Temperature of dew-point in degrees Fahrenheit.

Pressure = 29.0 inches.

Air temp. t	Vapor press. •	Depression of wet-bulb thermometer (<—<').
8.5	9.0	9.5	10.0	10.5	11.0	11.5	12.0	12.5	13.0	13.5	14.0	14.5	15.0	15.5 16.0
26	0.136	-53														1
27	.143	-32
28	.150	-23	-45
29	.157	-17	-29
30	0.164	-11	-20	-36
31	.172	- 7	-14	-24	-50
32	.180	- 4	- 9	-16	-29
33	.187	- 1	- 5	-11	-20	—36
34	.195	+ 2	- 2	- 7	— 14	-24	-50
35	0.203	5	+ 1	- 3	- 8	-16	-28
36	.211	8	4	± 0	- 4	-10	-19	-34
37	.219	10	7	+ *	- 1	- 6	-12	-22	-44
38	.228	12	9	6	+ 3	2	Y	-14	-25
39	.237	14	12	9	6	+ 2	- 3	- 8	-16	-30
40	0.247	16	14	11	8	5	+ 1	- 4	-10	-18	-35
41	.256	18	16	13	11	8	4	± 0	- 5	-11	-21	-45
42	.266	19	17	15	13	10	7	+ 4	^ -I	- 6	-13	-24	-59
43	.277	21	19	17	15	13	10	7	+ 3	- 2	- 7	-15	-28
44	.287	23	21	19	17	15	12	9	6	+ 2	- 2	- 8	-17	-32
45	0.298	24	22	20	19	17	14	11	8	6	+ 2	- 3	- 9	-18	-37
46	.310	25	24	22	20	18	16	14	11	8	5	+ 1	- 4	-11	-20	-44
47	.322	27	25	24	22	20	18	16	13	11	8	4	± 0	— 5	-12	-23	-53
48	.334	28	27	25	23	22	20	18	15	13	1C	7	+ *	- 1	- 6	—13	-25
49	.347	29	28	27	25	23	21	20	17	15	13	10	7	+ 3	- 2	- 7	-15
50	0.360	31	29	28	27	25	23	21	19	17	15	12	9	6	+ 2	- 2	- 8
51	.373	32	31	29	28	26	25	23	21	19	17	15	12	9	6	+ 2	- 3
52	.387	34	32	31	29	28	26	25	23	21	19	17	14	12	9	5	+ 1
53	.402	35	34	32	31	29	28	26	24	23	21	19	16	14	11	9	5
54	.417	36	35	34	32	31	29	28	26	24	S3	21	19	16	14	11	8
55	0.432	38	36	35	34	32	31	29	28	26	24	23	21	19	16	14	11
56	.448	39	38	36	35	34	32	31	29	28	26	24	23	21	19	16	14
57	.465	40	39	38	36	35	34	32	31	29	28	26	24	22	21	18	16
58	.482	42	40	39	38	36	35	34	32	31	29	28	26	24	22	20	18
59	.499	43	42	40	39	38	37	35	34	32	31	29	28	26	24	22	20
60	0.517	44	43	42	41	39	38	37	35	34	32	31	29	28	26	24	22
61	.536	45	44	43	42	41	39	38	37	35	34	32	31	29	28	26	24
62	.555	47	46	44	43	42	41	40	38	37	35	34	32	31	30	28	26
63	.575	48	47	46	45	43	42	41	40	38	37	36	34	33	31	30	28
64	.595	49	48	47	46	45	44	42	41	40	38	37	36	34	33	31	30
65	0. 616	50	49	48	47	46	45	44	43	41	40	39	37	36	34	33	31
66	.638	52	51	50	48	47	46	45	44	43	42	40	39	37	36	35	33
67	.601	53	52	51	50	49	48	46	45	44	43	42	40	39	38	36	35
68	.684	54	53	52	51	50	49	48	47	46	44	43	42	41	39	38	36
69	.707	55	54	53	52	51	50	49	48	47	46	45	43	42	41	40	38
70	0.732	56	55	54	53	52	51	50	49	48	47	46	45	44	42	41	40
71	.757	58	57	56	55	54	53	52	51	50	49	47	46	45	44	43	41
72	.783	59	58	57	56	55	54	53	52	51	50	49	48	46	45	44	43
73	.810	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	44
74	.838	61	60	59	58	57	56	55	54	54	53	52	50	49	48	47	46
75	0.866	62	61	60	60	59	58	57	56	55	54	53	52	51	50	48	47
76	.896	63	62	62	61	60	59	58	57	56	55	54	53	52	51	50	49
77	.926	64	64	63	62	61	60	59	58	57	56	55	54	53	52	51	50
78	.957	66	65	64	63	62	61	60	59	59	58	57	56	55	54	53	52
79	0.989	67	66	65	64	63	62	62	61	60	59	58	57	56	55	54	53
80	1.022	68	67	66	65	64	64	63	62	61	60	59	58	57	56	55	54

DEW-POINT

28

TABLE II.— Temperature of dew-point in degrees Fahrenheit.

Pressure = 29.0 inches.

Air	Depression of wet-bulb thermometer (t—f).
tCIHJ). t	16.5	17.0	17.5	18.0	18.5	19.0	19.5	20.0	20.5	21.0	21.5	22.0	22.5	23.0	23.5	24.0
49	-28
50	-17	-32
61	—10	-18	-37
52	- 4	-11	-20	-45
53	± 0	- 5	-12	—23	-55
54	+ 6	± 0	— 6	-13	-25
55	8	+ *	-\	- 6	-14	-27
66	11	7	+ 4	- 1	- 7	-16	-30
57	13	10	7	+ 3	- 2	- 8	-17	-33
58	16	13	10	7	+ 3	- 2	— 9	-18	-37
59	18	16	13	10	7	+ 2	- 3	- 9	-19	-41
60	20	18	16	13	10	6	+ 2	- 3	-10	-20	-46
61	22	20	18	16	13	10	6	+ 2	- 3	-10	-21,	-51
62	24	22	20	18	16	13	10	6	+ 2	- 4	-11	-22	—59
63	26	24	22	20	18	16	13	10	6	+ 2	— 4	-11	-23
64	28	26	25	23	21	18	16	13	10	6	+ 1	- 4	-12	-24
65	30	28	26	25	23	21	18	16	13	10	6	+ 1	— 4	-12	—25
66	31	30	28	27	25	23	21	18	16	13	10	6	+ 1	- 4	-12	-26
67	33	32	30	29	27	25	23	21	19	16	13	10	6	+ 1	— 4	-12
68	35	33	32	30	29	27	25	23	21	19	16	13	10	6	+ 1	- 4
69	37	35	34	32	31	29	27	25	23	21	19	16	13	10	6	+ 1
70	38	37	35	34	32	31	29	27	25	23	21	19	16	13	10	6
71	40	38	37	36	34	32	31	29	27	26	24	21	19	17	14	10
72	42	40	39	37	36	34	32	31	29	28	26	24	21	19	17	14
73	43	42	40	39	38	36	34	33	31	30	28	'26	24	22	19	17
74	45	43	42	41	39	38	36	35	33	32	30	28	26	24	22	20
75	46	45	44	42	41	40	38	37	35	33	32	30	28	26	24	22
76	48	46	45	44	43	41	40	38	37	35	34	32	30	29	27	25
77	49	48	47	46	44	43	42	40	39	37	36	34	32	31	29	27
78	50	49	48	47	46	44	43	42	41	39	38	36	34	33	31	29
79	52	51	50	49	47	46	45	44	42	41	39	38	36	35	33	31
80	53	52	51	50	49	48	46	45	44	43	41	40	38	37	35	33
|	Depression of wet-bulb thermometer (<—<')•
	24.5	25.0	25.5	26.0	26.5	27.0	27.6	28.0	28.5	29.0	29. 5 30. 0	30.5	31.0	31.6
67	-26
68	-12	-26
69	- 4	-13	-27
70	+ 1	- 4	-12	-27
71	6	+ 2	- 4	-12	-26
72	10	7	+ 2	- 4	-12	-26
73	14	11	7	+ 2	— 4	-12	-26
74	17	14	11	7	+ 2	- 3	-12	-25
75	20	17	14	11	7	+ 3	- 3	-11	-25
76	23	20	18	15	11	8		- 3	-10	-24
77	25	23	20	18	15	12	8	+ 3	- 2	-10	-22
78	27	25	23	21	18	15	12	8	+ 4	- 2	- 9 -21
79	29	28	26	24	21	19	16	13	9	+ 4	- 1 - 9	-ao
80	31	30	28	26	24	22	19	16	13	9	+ 5 - 1	- 8	-19	-64

DEW-POINT

29

TABLE II. ~ Temperature of dew-point in degrees Fahrenheit.

Pressure = 29.0 inches.

Air ;emp. t	Vapor press. e	Depression of wet-bulb thermometer (I — tT).
1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
80	1.022	79	77	76	75	73	72	70	69	67	65	64	62	60	58	56
81	.056	80	78	77	76	74	73	71	70	68	6«	65	63	61	60	58
	.091	81	79	78	77	75	74	72	71	69	68	66	64	63	61	59
83	.127	82	80	79	78	76	75	73	72	70	69	67	65	64	62	60
84	.163	83	81	80	79	77	76	74	73	71	70	68	67	65	63	61
85	1.201	84	82	81	80	78	77	75	74	72	71	69	68	66	64	63'
86	.241	85	83	82	81	79	78	77	75	74	72	71	69	67	66	64
87	.281	86	84	83	82	80	79	78	76	75	73	72	70	69	67	65
88	.322	87	85	84	83	81	80	79	77	76	74	73	71	70	68	66
89	.364	88	86	85	84	82	81	80	78	77	75	74	72	71	69	68
90	1.408	89	87	86	85	84	82	81	79	78	77	75	74	72	70	69
91	.453	90	88	87	86	85	83	82	80	79	78	76	75	73	72	70
92	.499	91	90	88	87.	86	84	83	82	80	79	77	76	74	73	71
93	.546	92	91	89	88	87	85	84	83	81	80	78	77	75	74	72
94	.595	93	92	90	89	88	86	85	84	82	81	80	78	77	75	74
95	1.645	94	93	91	90	89	87	86	85	83	82	81	79	78	76	75
96	.696