changes, omitting temperature and winds at first. Include in your weather
forecasts the state of the sky (_clear_, _fair_, _cloudy_); the changes in
the state of the sky (increasing or decreasing cloudiness); the kind of
precipitation (_rain_ or _snow_) and the amount of precipitation (_light_
or _heavy_). Write out your forecasts; compare them with the official
forecasts, and notice how fully they are verified. Then add temperature
and winds to your forecasts so that you will make a complete prediction of
probable changes in temperature (kind, amount, and rapidity of change),
wind (direction and velocity), and weather. Practice making these complete
forecasts for several weeks, if time allows. Use all the knowledge that
you have gained in the preceding work to aid you in this. Study each
weather map very carefully. Do not write down your forecast until you are
sure that you have done the best you can.
[Illustration: FIG. 53.]
Vary this exercise by extending your forecasts so as to embrace the whole
section of country in which your station is situated (as, _e.g._, New
England, the Gulf States, the Lake region). Pay special attention to
making forecasts of cold waves, of heavy rain or snowstorms, of high
winds over the lakes or along the Atlantic coast, etc. When possible,
obtain from the daily newspapers any particulars as to damage done by
frost or gales, or concerning snow blockades, floods due to heavy rains,
etc.
Fig. 53 summarizes what has thus far been learned as to the distribution
of the various weather elements around a well-developed center of low
pressure. The curved broken lines represent the _isotherms_ (Chapter XIV).
The solid concentric oval lines are the _isobars_ (Chapter XI). The arrows
represent the _winds_, the lengths of the arrows being roughly
proportionate to the wind velocities (Chapter XII). The whole shaded area
represents the region over which the sky is covered by heavy lower clouds.
The smaller shaded area, within the larger, encloses the district over
which rain or snow is falling (Chapter XVI). The lines running out in
front of the cloudy area represent the light upper clouds (_cirrus_ and
_cirro-stratus_) which usually precede an area of low pressure.
Imagine this whole disturbance moving across the United States in a
northeasterly direction, and imagine yourself at a station (1) directly in
the path of the cyclone; (2) south of the track; and (3) north of the
track. In the first case, as the disturbance moved on in its path, you
would successively occupy the positions marked _A_, _B_, and _C_ on the
line _AC_, passing through the center of the cyclone. In the second case
you would be first at _D_, then at _E_, and then at _F_. In the third case
you would be at _G_, _H_, and _J_ in succession. What changes of weather
would you experience in each of these positions as the cyclone passed by
you? Imagine yourself at some station halfway between the lines _AC_ and
_DF_. What weather changes would you have in that position with reference
to the storm track? In what respects would these weather changes differ
from those experienced along the line _DF_? Imagine your station halfway
between the lines _AC_ and _GJ_. What weather changes would you have
there? How would these changes differ from those experienced along the
line _GJ_?
It must be remembered that Fig. 53 is an ideal diagram. It represents
conditions which are not to be expected in every cyclone which appears on
our weather maps. If all cyclones were exactly alike in the weather
conditions around them, weather forecasting would be a very easy task. But
cyclones are not all alike——far from it. Some are well developed, with
strong gradients, high winds, extended cloud areas, heavy precipitation,
and decided temperature contrasts. Others are but poorly developed, with
weak gradients, light winds, small temperature differences, and it may be
without any precipitation whatever. Some cover immense districts of
country; others are small and affect only a limited area. It therefore
becomes necessary to examine the characteristics of each approaching
cyclone, as shown on the daily weather map, very carefully. Notice whether
it is accompanied by heavy rain or snow; whether its winds are violent;
how far ahead of the center the cloudy area extends; how far behind the
outer cloud limit the rain area begins; what is the position of the cloud
and rain area with reference to the center, and other points of equal
importance, and govern yourself, in making your forecast, according to the
special features of each individual cyclone. Well-developed cyclones will
be accompanied by marked weather changes. Weak cyclones will have their
weather changes but faintly marked.
The distance of your station from the center of the cyclone is of great
importance in determining what the weather conditions and changes shall
be, as may easily be seen by examining Fig. 53. If the storm passes far to
the north or far to the south of your station, you may notice none of its
accompanying weather conditions, except, perhaps, a bank of clouds on your
horizon. You may for a few hours be under the cloudy sky of some passing
storm, and yet not be reached by its rainy area. The shifts in the wind
may be marked and the wind velocities high, or the expected veering or
backing may hardly be noticeable, owing to the weakness or the distance of
the controlling cyclone.
Again, the rapidity with which weather conditions will change depends upon
the rate of movement of the cyclone itself. The better developed the
cyclone, the higher its velocity of progression, and the nearer its track
lies to the station, the more emphatic and the more rapid are the weather
changes it causes. On the other hand, the weaker the cyclone, the slower
its rate of progression, and the further away its track, the less marked
and the slower the weather changes. The probable track of a coming storm,
and its probable rate of movement, therefore, need careful study if our
forecasts are to be reliable.
There are many other obstacles in the way which combine to render weather
forecasting extremely difficult. Some of these difficulties you will learn
to overcome more or less successfully by the experience you will gain from
a careful and persevering study of the daily weather maps; others, the
best forecast officials of our Weather Bureau have not yet entirely
overcome. The tracks followed by our cyclones vary more or less from month
to month, and even if the average tracks for each month are known,
individual cyclones may occur which absolutely disregard these tracks.
While the average hourly velocity of cyclones is accurately known for the
year and for each month, the movements of individual storms are often very
capricious. They may move with a fairly uniform velocity throughout the
time of their duration; they may suddenly and unexpectedly increase their
rate of movement, or they may as suddenly come nearly to a standstill. The
characteristics of cyclones vary in different portions of the country and
at different times. Cyclones which have been accompanied by little
precipitation on most of their journey are apt to give increased rain or
snowfall as they near the Atlantic Ocean and Gulf of St. Lawrence.
Cyclones which over one portion of the country were rainy, may give little
or no precipitation in another portion. Cyclones and anticyclones are
found to have considerable influence on one another, retarding or
accelerating one another’s advance, or changing one another’s normal path
of progression. While this mutual interaction is clearly seen, and may be
successfully predicted in many cases, many other cases arise in which,
under apparently similar conditions, the result is very different from the
anticipation. Such are some of the difficulties with which weather
forecasters have to contend, and which prevent the attainment of greater
accuracy in weather prediction.
PART V.——PROBLEMS IN OBSERVATIONAL
METEOROLOGY.
CHAPTER XX.
TEMPERATURE.
The chief interest and value of the instrumental work in meteorology are
to be found not only in the taking of the daily observations at stated
hours, but in the working out of numerous simple problems, such as may
readily be undertaken with the help of the instruments already described.
Thus, the temperature of the air (obtained by the sling thermometer,
supplemented by maximum and minimum thermometers, and by the thermograph
if available) can be determined under a variety of conditions, _e.g._,
close to the ground, and at different heights above the ground; at
different hours, by day and night; in different seasons; in sunshine and
in shade; during wind and calms; in clear and cloudy weather; in woods and
in the open; over bare ground, grass, snow, or ice; on hills and in
valleys. Observations may also be made of the temperature of the ground
and of a snow cover, at the surface and at slight depths beneath the
surface, in different seasons and under different weather conditions.
Among the problems which may be worked out by means of such observations
as these are the following:——
_A._ =The Diurnal Range of Temperature under Different Conditions and at
Different Heights above the Ground.=——Under the influence of the sun the
regular normal variation of temperature during 24 hours is as follows: A
gradual increase, with the increasing altitude of the sun, from sunrise
until shortly after noon, and a gradual decrease, with decreasing altitude
of the sun, from the maximum, shortly after noon, until the minimum, about
sunrise. This variation is known as the _diurnal variation of
temperature_. Curve _a_ in Fig. 12 illustrates well the normal diurnal
variation of temperature, as recorded by the thermograph during a period
of clear, warm spring weather (April 27-30, 1889, Nashua, N. H.). The
_diurnal range of temperature_ is the difference between the maximum and
minimum of the diurnal oscillation. The regular normal diurnal variation
in temperature is often much interfered with by other controlling causes
than the sun, _e.g._, cyclonic winds, clouds, etc.
I. Study and compare the diurnal ranges of temperature as indicated by the
maximum and minimum thermometers, or the thermograph, in the instrument
shelter, in clear, fair, cloudy, and stormy weather, during winds and in
calms, in different months. Summarize your results by grouping them
according to the general weather conditions, and according to the months
or seasons in which the observations were made. For example, group
together and average the ranges observed on clear, calm days in winter; on
similar days in early summer or autumn; on clear days with brisk northwest
winds in winter; on similar days in early summer or autumn; on calm days
with overcast sky in the different seasons; on stormy days with strong
winds, etc. Study carefully the weather maps for the days on which your
observations are made. Pay special attention to the relation between the
diurnal ranges and the control exercised over these ranges by cyclones and
anticyclones through their winds and general weather conditions.
II. Observations of diurnal ranges of temperature at different heights
above the ground may be made by means of maximum and minimum thermometers
fastened (temporarily) outside of the windows of different stories of the
school or of some other building. These observations should be made out of
windows facing north, and care should be taken to check, so far as
possible, any draft from within the building out through the window during
the taking of the observation. If a fire escape is provided on the
building, the instruments may often be conveniently fastened to that.
Study the ranges under different conditions of wind and weather at various
heights above the ground, and compare these results with those obtained
under I. Notice the relations of all your results to the cyclonic and
anticyclonic areas of the weather maps.
The diurnal range of temperature in the air over the open ocean from the
equator to latitude 40° has been found to average only 2° to 3°. In
southeastern California and the adjacent portion of Arizona the average
diurnal temperature range in summer is 40° or 45°. Over other arid
regions, such as the Sahara, Arabia, and the interior of Australia, the
range also often amounts to 40°. Observations of temperature above the
earth’s surface, in the free air, made on mountains, in balloons, and by
means of instruments elevated by kites, indicate very clearly that the
diurnal range of temperature decreases with increasing elevation above
sea level. The results obtained at Blue Hill Observatory, Massachusetts,
by means of kites, show that the diurnal range of temperature almost
disappears, on the average, at 3300 feet (1000 meters).
_B._ =Changes of Temperature in the Lower Air, and their Control by the
Condition of the Ground, the Movement of the Air, and Other
Factors.=——Determine the changes of the temperature in the lower air by
making frequent readings of the ordinary thermometer in the instrument
shelter, of the sling thermometer, or by an examination of the thermograph
record. Group these changes, as in Problem _A_, so far as possible
according to the weather conditions under which they occurred, and try to
classify the kinds of change roughly into types. Study the control of
these various types by the wind and other weather conditions accompanying
them, as illustrated on the daily weather maps. The control exercised by
different conditions of the earth’s surface may be studied by means of
observations made with the sling thermometer over different surfaces, such
as grass, bare ground, snow, etc.
Examples of temperature changes in the lower air, under different
conditions of weather, recorded on the thermograph, are given in Fig. 12,
and are briefly referred to their causes in the text accompanying that
figure.
_C._ =Vertical Distribution of Temperature in the Atmosphere.=——The
vertical distribution of temperature in the lower air may be studied by
having ordinary thermometers or thermographs exposed at different heights
above the ground, _e.g._, close to the surface; in an instrument shelter;
out of windows on successive stories of some high building; and on the
roof of the building. They may also, in cases where there is a hill in the
neighborhood, be exposed in a valley at the bottom of the hill and at
successive elevations up the side of the hill. It is, however, usually
much simpler, as well as more practicable, to take these temperature
readings by means of the sling thermometer. In the case of observations
made out of the windows of a building, one observer can take the readings
at different elevations in succession. When the observations are made at
different altitudes on the side of a hill, it is best to have the
coöperation of several observers, who shall all read their thermometers at
the same moment of time. The results obtained in the previous problems
(_A_ and _B_) may, of course, also be utilized in studying the vertical
distribution of temperature in the atmosphere.
Study the vertical distribution of temperature in the lower air under
various conditions of weather and season; at various hours of the day, and
with varying conditions of surface cover. Make your observations
systematically, at regular hours, so that the results may be comparable.
Group together observations made under similar conditions of weather,
season, time, and surface cover. Determine the average vertical
distribution of temperature in the different cases. Note especially any
seeming peculiarities or irregularities in this distribution at certain
times. Study carefully, as in the previous problems, the relation of the
different types of temperature distribution in the atmosphere to the
weather conditions as shown on the daily weather maps.
Observations made in different parts of the world, on mountains and in
balloons, have shown that on the average the temperature decreases from
the earth’s surface upwards at the rate of about 1° in 300 feet of
ascent. The rate of vertical decrease of temperature is known in
meteorology as the _vertical temperature gradient_. When it happens that
there is for a time an _increase in temperature upwards_ from the earth’s
surface, the condition is known as an _inversion of temperature_.
As a result of the decrease of temperature with increasing altitude above
sea level, the tops of many high mountains even in the Torrid Zone are
always covered with snow, while no snow can ever fall at their bases,
owing to the high temperatures which prevail there. Balloons sent up
without aëronauts, but with self-recording instruments, have given us
temperatures of -90° at a height of 10 miles above the earth’s surface. On
Dec. 4, 1896, Berson reached a height of 30,000 feet and noted a
temperature of -52°. Inversions of temperature are quite common,
especially during the clear cold spells of winter. Under such conditions
the tops and sides of hills and mountains are often much warmer than the
valley bottoms at their bases. A good example of an inversion of
temperature occurred in New Hampshire on Dec. 27, 1884. The pressure was
above the normal, the sky clear and the wind light. The observer on the
summit of Mt. Washington reported a temperature of +16° on the morning of
that day, while the thermometers on the neighboring lowlands gave readings
of from -10° to -24°. In Switzerland, the villages and cottages are
generally built on the mountain sides and not down in the valley bottoms,
experience having taught the natives that the greatest cold is found at
the lower levels.
CHAPTER XXI.
WINDS.
The determination of the direction of the wind (by means of the wind vane)
and of its velocity (by means of the anemometer, or by estimating its
strength) at different hours, under different conditions of weather and in
different seasons, leads to a number of problems. The following simple
investigations may readily be undertaken in schools:——
_A._ =The Diurnal Variation in Wind Velocity in Fair Weather.=——Observe
and record the velocity of the wind (either estimated or registered by the
anemometer) every hour, or as often as possible, on clear or fair days in
different months. Can you discover any regular change in the velocities
during the day? If so, what is the change? Does the season seem to have
any control over the results obtained? Examine the daily weather maps in
connection with your observations and determine the effect that different
weather conditions have upon the diurnal variation in wind velocity.
The diurnal variation in wind velocity over the open ocean is so slight
as hardly to be noticeable. Over the land, the daytime winds are commonly
strongest in arid regions. Traveling across the desert often becomes
extremely disagreeable, owing to the clouds of dust which these winds
sweep up from the surface.
_B._ =The Variations in Direction and Velocity due to Cyclones and
Anticyclones.=——Record the direction and velocity of the wind at your
station at frequent intervals during the passage of a considerable number
of cyclones and anticyclones. Enter your observations in some form of
table so that they may be readily examined. (See p. 113.) Note the
character of the changes that occur, classifying them into types, so far
as possible. Study the control of wind directions and velocities by the
special features of the individual cyclones and anticyclones as shown on
the daily weather maps. How are the different types of change in
direction and velocity affected by the tracks of cyclones and
anticyclones? By their velocity of progression? By the arrangement of
isobars around them? By the height of the barometer at the center? By the
season in which the cyclones and anticyclones occur?
Frequent changes in the direction and velocity of our winds are one great
characteristic of the Temperate Zones, especially in winter. The
continuous procession of cyclones and anticyclones across the United
States involves continuous shifts of wind. Over much of the earth’s
surface, however, the regularity and constancy of the winds are the
distinguishing feature of the climate. Over a considerable part of the
belts blown over by the northeast and southeast trades, roughly between
latitude 30° N. and S. and the equator, the winds keep very nearly the
same direction and the same velocity day after day and month after month.
Thus the trades are of great benefit to commerce. Sailing ships may
travel for days in the trade wind belts without having their sails
shifted at all, with a fair wind all the time carrying them rapidly on to
their destination.
_C._ =The Occurrence and Characteristics of Local Winds, such as Mountain
and Valley and Land and Sea Breezes.=——If the observer happens to be
living in or near the mouth of a valley or on a mountain side, opportunity
may be given for the observation of the local winds down the mountain
sides and down the valley at night, and up the valley and the mountain
sides by day, known as mountain and valley breezes. Keep a record of wind
direction and velocity during the day, and especially during the morning
and evening hours. Notice any marked changes in direction, and the
relation of these changes to the time of day. Does the velocity of the
daytime up-cast breeze show any systematic variation during the day? Study
the relation of mountain and valley breezes to the general weather
conditions shown on the weather maps. How are these breezes affected by
season? By the presence of a cyclone over the region? Of an anticyclone?
By the state of the sky?
If near the seacoast (_i.e._, within 10 or 15 miles), an interesting study
may be made of local land and sea breezes. The sea breeze is a wind from
the ocean onshore, while the land breeze blows offshore. These breezes
occur only in the warmer months. Take frequent observations during the
day, as in the case of mountain and valley winds, noting especially any
changes in direction and velocity, and the relation of these changes to
the time of day. Study also the control exercised by the prevailing
weather conditions over the occurrence and the strength of development of
the land and sea breezes.
This problem may be considerably extended by adding temperature
observations to the simpler record of wind direction and velocity.
In some of the Swiss valleys the mountain and valley breezes are such
regular daily weather phenomena that it has become a weather proverb that
a failure of the daily change in wind direction indicates a change of
weather. Special names are often given to these breezes where they are
well marked. In a part of the Tyrol sailing boats go up the lakes by day
with the valley breeze, and sail back at night with the mountain breeze.
It is therefore unnecessary for the boats to be rowed either way. Land
and sea breezes, although an unimportant climatic feature in these
northern latitudes, are often of the highest importance in the Torrid
Zone. The fresh pure sea breeze from over the ocean makes it possible for
Europeans to live in many tropical climates where otherwise they would
not keep their health. The land breeze, on the other hand, is apt to be
an unhealthy wind in the tropics, especially when it blows off of swampy
land.
CHAPTER XXII.
HUMIDITY, DEW, AND FROST.
The humidity of the air, as determined by the wet and dry-bulb
thermometers or the sling psychrometer, and the occurrence or absence of
dew or frost, should be studied together. Observations should be made at
different hours, in different kinds of weather, and in different seasons.
From such observations the following problems may be solved:——
_A._ =Diurnal Variation of Relative Humidity under Different
Conditions.=——Readings of the wet and dry-bulb thermometers in the
instrument shelter, or of the sling psychrometer, several times during the
day, will furnish data for determining the diurnal variation of relative
humidity. Classify your observations according to the weather conditions
under which they were made, and by months or seasons. Summarize the
results of your investigation, paying special attention to the relation
between the diurnal variation of relative humidity and the temperature.
The variations of relative humidity are generally the reverse of those of
absolute humidity. In the case of the latter the average diurnal
variations are small. The fluctuations in the relative humidity during
the day on the northwestern coast of Europe amount to about 7% in
December and 17% in August, while in central Asia they average about 25%
in winter and 50% in summer.
_B._ =Relation of Relative Humidity to the Direction of the
Wind.=——Observations by means of the wet and dry-bulb thermometers in the
shelter, or by means of the sling psychrometer, supplemented by records of
wind direction, will furnish data for the solution of this problem.
Tabulate your observations according to wind directions and seasons.
Determine the characteristics of the different winds as to their relative
humidities. Consider the control of these winds and humidity conditions by
cyclones and anticyclones.
The warm wave, or sirocco, in front of our winter cyclones in the eastern
United States is a damp, disagreeable, irritating wind. In summer, the
sirocco is usually dry, and during the prevalence of such winds we have
our hottest spells, when sunstrokes are not uncommon. In southern Italy
the sirocco has the same position with reference to the controlling
cyclone. There the wind is often so dry as seriously to injure
vegetation. The cold wave, on the rear of our winter cyclones, with its
low temperature and dry air, often comes as a refreshing change after the
enervating warmth of the preceding sirocco. Our feelings of bodily
comfort or discomfort are thus in a large measure dependent upon the
humidity and the movement of the air.
_C._ =The Formation of Dew.=——The formation of dew is to be studied from
the following points of view, viz., as dependent upon: _a_, the
temperature and the humidity of the air; _b_, the exposure and condition
of the ground; _c_, the state of the sky; and _d_, the movement of the
air. The occurrence of dew on any night, as well as the amount, whether
large or small, can readily be ascertained by inspection. Observe the
conditions of temperature, humidity, cloudiness, and wind direction and
velocity, as in previous exercises. Pay special attention to the state of
the sky, the wind movement, and the vertical distribution of temperature
near the ground. Under heading _b_ (exposure and condition of the ground)
make observations of the amounts of dew formed on hilltops, hillsides, and
in valleys; on different kinds of surface covering, as grass, leaves,
pavements, etc., and over different kinds of soil. Classify the results in
accordance with the conditions under which the observations were made.
Compare the results and draw your conclusions from this study. Practise
making predictions of the formation of dew in different places and under
different weather conditions.
Over the greater portion of the earth’s surface the amount of dew which
is deposited is very small. It has been estimated that in Great Britain
the total annual amount would measure only an inch and a half in depth;
and in central Europe the depth is given as hardly one inch. In some
parts of the Torrid Zone, on the other hand, dew is deposited in much
larger quantities. According to Humboldt, the traveler through some of
the South American forests often finds what seems to be a heavy shower
falling under the trees, while the sky is perfectly clear overhead. In
this case dew is formed on the tops of the tree in sufficiently large
quantities to give a shower underneath. It is reported that on the Guinea
coast of Africa the dew sometimes runs off the roofs of the huts like
rain. In many dry regions the dew is an important agency in keeping the
plants alive.
_D._ =The Formation of Frost.=——The formation of frost is to be studied in
the same way as that suggested in the case of dew, _i.e._, as dependent
upon: _a_, the temperature and the humidity of the air; _b_, the exposure
and condition of the ground; _c_, the state of the sky; and _d_, the
movement of the air. Frosts are usually classified as _light_ or _heavy_.
The words _killing frost_ are also used. Study the weather and surface
conditions which are most favorable to the formation of frost. Pay special
attention to the relation of frost and inversions of temperature; to the
frequency of frost on open or sheltered surfaces; on hills or in valleys,
and on the lower and upper branches of trees and shrubs. Determine, as
well as you can, the weather conditions which precede light or heavy
frosts, and make predictions of coming frosts, when the conditions warrant
them.
Our Weather Bureau gives much attention to the prediction of frosts and
to the prompt and widespread distribution of frost warnings. Growing
crops and fruits are often seriously injured by frosts, and farmers are
naturally anxious to have as early warning as possible of their
occurrence. Various methods of protecting crops and trees against frost
are used. The method most commonly employed consists in the building of
fires of brush or other inflammable material on the windward side of the
field or the orchard when a frost is expected. The smoke from the fire is
blown to leeward across the field, and acts as an artificial cloud,
affording protection to the vegetation underneath. Such fires are known
as _smudges_.
CHAPTER XXIII.
CLOUDS AND UPPER AIR CURRENTS.
Attentive observation of clouds will soon lead to a familiarity with their
common type forms. A series of cloud views,[7] with accompanying
descriptive accounts, will teach the names of the clouds and give
definiteness to the record. The directions of movement of clouds are
determined by means of the nephoscope. Cloud observations should be made
at different hours, in different weather conditions, and in different
seasons. The following problems are concerned with clouds and upper air
currents:——
[Footnote 7: See _Hydrographic Office Cloud Types_, Appendix B.]
_A._ =The Typical Cloud Forms and their Changes.=——Note carefully the
characteristic forms assumed by clouds; their mode of occurrence, whether
in single clots, or in groups, in lines, or all over the sky; their
changes in form and in mode of occurrence. Classify and summarize your
results. Compare the clouds of the warm months with those of the cold
months.
Observations have shown that clouds have certain definite characteristic
forms which are substantially the same in all parts of the world. This
fact makes it possible to give names to the different typical forms, and
these names are used by observers the world over. Hence cloud
observations, wherever made, are comparable. The first classification of
clouds was proposed by Luke Howard, in 1803. The classification at
present in use is known as the _International Classification_, and was
adopted by the International Meteorological Congress in 1896.
_B._ =The Prevailing Direction of Cloud Movements.=——The use of the
nephoscope is necessary in the accurate determination of cloud movements.
Study the prevailing directions of movement of the clouds, by means of
frequent observations with the nephoscope, in different weather
conditions. Separate the upper and lower clouds in this study. Summarize
your results according to the weather conditions and the kinds of clouds.
_C._ =Correlation of Cloud Form and Movement with Surface Winds, with
Cyclones and Anticyclones, and with Weather Changes.=——The results
obtained in the working out of the two preceding problems may be used in
the present problem. Tabulate your observations of cloud forms with
reference to the wind directions which prevailed at the time of making the
observations. Do the same with the directions of cloud movement. Determine
the relation between surface winds and cloud types, and between surface
winds and the direction of the upper air currents, as shown by the
movements of the upper clouds. Study the control exercised by cyclones and
anticyclones over cloud forms and over the direction of the upper air
currents.
_D._ =The Use of Clouds as Weather Prognostics.=——Attentive observation of
the forms and changes of clouds, and of the accompanying and following
weather changes, will lead to the association of certain clouds with
certain coming weather conditions. Make your cloud observations carefully,
taking full notes at the time of observation. Give special attention to
the weather conditions that follow. Continue this investigation through as
long a period as possible, until you have gathered a considerable body of
fact to serve as a basis, and then frame a set of simple rules for
forecasting fair or stormy weather on the basis of the forms and changes
of the clouds. Such local observations as these may be employed as a help
in making forecasts from the daily weather maps.
Clouds were used as weather prognostics long before meteorological
observations and weather maps were thought of. To-day sailors and farmers
still look to the clouds to give them warning of approaching storms. Many
of our common weather proverbs are based on the use of clouds as weather
prognostics.
CHAPTER XXIV.
PRECIPITATION.
The special study of various problems connected with precipitation
involves detailed observations of the amount and rate of precipitation of
various kinds, measured by the rain gauge during storms in different
seasons. These observations of precipitation should, of course, be
supplemented by the usual record of the other weather elements. The
following problems are suggested:——
A. _The relation of precipitation in general to the other weather
elements, and to cyclones and anticyclones._
B. _The conditions under which special forms of precipitation (rain, snow,
sleet, hail, frozen rain) occur._
C. _The conditions associated with light and heavy, brief and prolonged,
local and general rainfall._
These problems are studied by means of a careful comparison of full
weather records with the daily weather maps during a considerable period
of time.
Rain is the most common form of precipitation the world over, although
snow falls over large portions of both hemispheres. In the Arctic and
Antarctic zones almost all the precipitation, which is small in amount,
comes in the form of snow. In southern Europe snow falls at sea level
during the winter as far south as 36° north latitude on the average. In
eastern Asia snow occasionally falls as far south as 23° north latitude.
The mean annual rainfall varies greatly in different parts of the world.
In desert regions it is practically nothing. At Cherrapunjee, in India,
it reaches 493 inches, or over 40 feet. A fall of 40.8 inches in a single
day occurred at this station on June 14, 1876. In the United States,
Upper Mattole, Cal., had an extraordinary monthly rainfall of 41.63
inches in January, 1888. An excessive daily rainfall of 8 inches occurred
at Syracuse, N. Y., on June 8, 1876. At Washington, D. C., 2.34 inches
fell in 37 minutes on June 27, 1881. A sudden and very heavy fall of rain
occurred at Palmetto, Nevada, in August, 1890. A rain gauge which was not
exposed to the full intensity of the storm caught 8.80 inches of water in
one hour. In August, 1891, an observer at Campo, Cal., measured 11.5
inches as the rainfall in one hour from one very heavy downpour, and from
a portion of a second storm.
CHAPTER XXV.
PRESSURE.
The variations of atmospheric pressure, although insensible to
non-instrumental observation, are so intimately connected with atmospheric
processes that they deserve careful attention. Their observation leads to
several problems.
_A._ =The Decrease of Pressure with Height, as between Valley and Hill, or
between the Base and Top of a Building.=——Make these observations with the
mercurial barometer, if possible. Note the air temperatures at the two
levels at which the barometer readings are made. Determine the heights of
hill or building by means of the following rule: Multiply by 9 the
difference in barometrical readings at the two stations, given in
hundredths of an inch, and the result will be approximately the difference
in height between the stations in feet. A more accurate result may be
reached by means of the following rule: The difference of level in feet is
equal to the difference of the pressures in inches divided by their sum,
and multiplied by the number 55,761, when the mean of the air temperatures
of the two places is 60°. If the mean temperature is above 60°, the
multiplier must be increased by 117 for every degree by which the mean
exceeds 60°; if less than 60°, the multiplier must be decreased in the
same way. For example, if the lower station has a pressure of 30.00
inches and a temperature of 62°, and the upper station has 29.00 inches
and 58° respectively, the difference of level between the two will be
(30.00 - 29.00) / (30.00 + 29.00) × 55,761 = 945 feet.
If the lower values are 30.15 inches and 65°, while the upper values are
28.67 inches and 59°, then the formula becomes
(30.15 - 28.67) / (30.15 + 28.67) × [55,761 + (2 × 117)] = 1409 feet.
The determination of heights by means of the barometer depends upon the
fact that the rate of decrease of pressure upwards is known. As the
weight of a column of air of a given height varies with the temperature
of the air, it is necessary, in accurate work of this sort, to know the
air temperatures at both the lower and upper stations at the time of
observation. From these temperatures the mean temperature of the air
column between the two stations may be determined. Tables have been
published which facilitate the reductions in this work. The heights of
mountains are usually determined, in the first instance, by means of
barometric observations, carried out by scientific expeditions or by
travelers that have been able to reach their summits. More accurate
measurements are later made, when possible, by means of trigonometrical
methods.
_B._ =The Diurnal and Cyclonic Variation of Pressure in Different
Seasons.=——This problem is satisfactorily solved only by a study of the
curves traced by the barograph, or by plotting, as a curve, hourly or
half-hourly readings of the mercurial barometer. The _diurnal variation of
the barometer_ is the name given to a slight double oscillation of
pressure, with two maxima and two minima occurring during the 24 hours.
This oscillation is in some way, not yet understood, connected with the
diurnal variation in temperature. It is most marked in the tropics and
diminishes towards the poles. Fig. 15 illustrates, in the May curve, the
diurnal variation of the barometer at Cambridge, Mass., during a spell of
fair spring weather, May 18-22, 1887. The maxima are marked by + and the
minima by 0. The _cyclonic variation of pressure_ is the name given to
those irregular changes in pressure which are caused by the passage of
cyclones and anticyclones. The second curve in Fig. 15 shows the cyclonic
variations in pressure recorded by the barograph at Cambridge, Mass.,
during a spell of stormy weather, Feb. 23-28, 1887. These curves serve as
good illustrations of these two kinds of pressure variations.
Study your barograph tracings, or your barometer readings, as illustrating
diurnal or cyclonic variations of pressure. Note the character and the
amount of the diurnal and cyclonic variations, and their dependence on
seasons.
Over the greater part of the Torrid Zone the diurnal variation of the
barometer is remarkably distinct and regular. Humboldt first called
attention to the fact that in those latitudes the time of day may be told
within about 15 minutes if the height of the barometer is known.
_C._ =The Relation of Local Pressure Changes to Cyclones and Anticyclones,
and thus to Weather Changes.=——Make a detailed study of the relation of
the local pressure changes at your station, as shown by the barograph
curves, or by frequent readings of the mercurial or aneroid barometers, to
the passage of cyclones and anticyclones, and to their accompanying
weather changes. Classify the simple types of pressure change, so far as
possible, together with the general weather conditions that usually
accompany these types. Apply the knowledge of local weather changes thus
gained when you make your forecast on the basis of the daily weather
maps.
CHAPTER XXVI.
METEOROLOGICAL TABLES.
The tables which follow are those which are now in use by the United
States Weather Bureau. They were first published in the _Instructions for
Voluntary Observers_ issued in 1892, and were reprinted in 1897. The
following instructions will be found of service in the use of the
tables:——
TABLE I.——DEW-POINT.
The figures in heavy type, arranged in vertical columns at each side of
the page, are the _air temperatures_ in degrees Fahrenheit, as recorded by
the dry-bulb thermometer. The figures in heavy type, running across the
page, denote the _differences_, in degrees and tenths of degrees, _between
the dry-bulb and wet-bulb readings_, or, technically, the _depression of
the wet-bulb thermometer_. The figures in the vertical columns denote the
_dew-points_. Make your observation of the wet and dry-bulb thermometers
and note the difference between the two readings. Find, in the vertical
columns of heavy type, the temperature corresponding to your dry-bulb
reading, or the nearest temperature to that. Then look along the
horizontal lines of figures in heavy type for the figure which corresponds
exactly, or most nearly, with the difference between your wet and dry-bulb
readings. Look down the vertical column under this latter figure until you
reach the horizontal line corresponding to your dry-bulb reading. At this
point the figures in the vertical column give the dew-point of the air at
the time of your observation.
_Example_: Air Temperature (dry bulb), 47°; Wet Bulb, 44°; Difference, 3°.
On page 148 will be found the table containing both 47° (dry bulb) and 3°
(depression of the dew-point). In the twenty-eighth line of this table and
in the seventh column will be found the dew-point, viz., 41°.
_Example_: Air Temperature, 61.5°; Wet Bulb, 55.5°; Difference, 6°.
In this case 61.5° is not found in the vertical columns of dry-bulb
readings, but 61° and 62° are found. The dew-point, with a difference
between wet and dry-bulb readings of 6°, for an air temperature of 61°, is
50°; for an air temperature of 62°, it is 52°. Evidently, then, for an air
temperature of 61.5° the dew-point will be 51°, _i.e._, halfway between
50° and 52°. This method of determining dew-points at air temperatures or
with depressions of the wet-bulb thermometer which are not given exactly
in the tables, is known as _interpolation_.
_Example_: Air Temperature, 93°; Wet Bulb, 90.5°; Difference, 2.5°. Our
table gives no dew-points for wet-bulb depressions of 2.5°, with air
temperature 93°, but we find (on page 152) that for air temperature 93°
and depression of wet bulb of 2°, the dew-point is 91°, while for a
wet-bulb depression of 3°, the dew-point is 89°. By the method of
interpolation we can readily determine the dew-point in the special case
under consideration as 90°, _i.e._, halfway between 89° and 91°.
TABLE II.——RELATIVE HUMIDITY.
The general plan of this table is the same as that of Table I. The figures
in the vertical columns are the relative humidities (in percentages)
corresponding to the different readings of the wet and dry-bulb
thermometers.
TABLE III.——REDUCTION OF BAROMETER TO 32°.
The figures in heavy type, arranged in vertical columns at the left of the
page, refer to the temperature in degrees Fahrenheit, as indicated by the
attached thermometer. The figures in heavy type, running across the top
of the page, are the barometer readings in inches and tenths. Make a
reading of the attached thermometer and of the barometer. Find in the
vertical column the temperature corresponding to the reading of the
attached thermometer, and in the horizontal line of heavy figures the
reading corresponding to the height of the barometer. The decimal in the
vertical column, under the appropriate barometer reading, and in the same
horizontal line with the appropriate thermometer reading, is to be
subtracted from the height of the barometer as observed, thus correcting
the reading to freezing. When the attached thermometer reads below 28°,
the correction is additive.
_Example_: Attached Thermometer, 69°; Barometer, 30.00 inches; Correction,
-.110; Corrected reading, 29.890 inches.
_Example_: Attached Thermometer, 73°; Barometer, 29.75 inches; Correction
= ?
We do not find any column corresponding to a barometer reading of 29.75
inches. We do find, however, that with a barometer reading of 29.50, and
an attached thermometer reading of 73, the correction is -.118 inch, and
with a barometer reading of 30.00, the correction is -.120. By
interpolating, as in the case of the humidity table above, we find the
correction for a barometer reading of 29.75 inches, and an attached
thermometer reading of 73°. The correction is -.119, and the corrected
reading is 29.75 - .119 = 29.63 inches.
TABLE IV.——REDUCTION OF BAROMETER TO SEA LEVEL.
The figures in heavy type, in the left-hand vertical columns, are the
heights, in feet, of the barometer above sea level. The figures in heavy
type at the top of the columns, running across the page, are the readings
of the ordinary thermometer. The numbers of inches and hundredths of
inches to be subtracted from the barometer reading (corrected for
temperature by Table III), for the different heights above sea level, are
given in the vertical columns.
The altitude above sea level of the city or town at which the observation
is made should be ascertained as accurately as possible from some
recognized authority, as, _e.g._, from a railroad survey; from Government
measurements, or from some engineer’s office. The correction to be made is
determined by a simple inspection of the table or by the method of
interpolation.
_Example_: Altitude of Barometer above sea level, 840 feet; Temperature of
the air, 40°; Correction, +.931 inch.
_Example_: Altitude of Barometer above sea level, 205 feet; Temperature of
the air, 45°; Correction = ?
Here 205 feet and 45° are neither of them found in the table. Hence a
double interpolation is necessary. For 200 feet and 40° the correction is
+.224 inch. For 200 feet and 50° the correction is +.220 inch. Hence for
200 feet and 45° the correction is +.222 inch. For 210 feet and 40° the
correction is +.235 inch. For 210 feet and 50° the correction is +.231
inch. Hence for 210 feet and 45° the correction is +.233 inch. Now for 205
feet we should have a correction midway between +.235 inch and +.233 inch
or +.234 inch.
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+================================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_) | _t_
(Dry +----+----+----+----+----+----+----+----+----+----+----+----+----+(Dry
ther.)|0°.2|0°.4|0°.6|0°.8|1°.0|1°.2|1°.4|1°.6|1°.8|2°.0|2°.2|2°.4|2°.6|ther.)
------+----+----+----+----+----+----+----+----+----+----+----+----+----+------
-40 | -52| | | | | | | | | | | | | -40
-39 | -50| | | | | | | | | | | | | -39
-38 | -49| | | | | | | | | | | | | -38
-37 | -48| | | | | | | | | | | | | -37
-36 | -46| | | | | | | | | | | | | -36
| | | | | | | | | | | | | |
-35 | -44| | | | | | | | | | | | | -35
-34 | -43| -58| | | | | | | | | | | | -34
-33 | -42| -55| | | | | | | | | | | | -33
-32 | -40| -52| | | | | | | | | | | | -32
-31 | -38| -49| | | | | | | | | | | | -31
| | | | | | | | | | | | | |
-30 | -36| -47| | | | | | | | | | | | -30
-29 | -35| -44| | | | | | | | | | | | -29
-28 | -33| -42| -56| | | | | | | | | | | -28
-27 | -32| -40| -52| | | | | | | | | | | -27
-26 | -30| -37| -48| | | | | | | | | | | -26
| | | | | | | | | | | | | |
-25 | -29| -35| -45| | | | | | | | | | | -25
-24 | -28| -34| -43| -58| | | | | | | | | | -24
-23 | -27| -32| -40| -53| | | | | | | | | | -23
-22 | -26| -30| -37| -49| | | | | | | | | | -22
-21 | -25| -29| -35| -45| | | | | | | | | | -21
| | | | | | | | | | | | | |
-20 | -23| -28| -33| -41| -55| | | | | | | | | -20
-19 | -22| -26| -31| -38| -50| | | | | | | | | -19
-18 | -21| -25| -29| -35| -45| | | | | | | | | -18
-17 | -20| -23| -27| -32| -41| -55| | | | | | | | -17
-16 | -19| -22| -26| -30| -37| -49| | | | | | | | -16
| | | | | | | | | | | | | |
-15 | -17| -20| -24| -28| -34| -44| | | | | | | | -15
-14 | -16| -19| -22| -26| -31| -39| -52| | | | | | | -14
-13 | -15| -18| -21| -25| -29| -35| -46| | | | | | | -13
-12 | -14| -17| -20| -23| -27| -32| -41| -55| | | | | | -12
-11 | -13| -16| -18| -21| -25| -30| -36| -48| | | | | | -11
| | | | | | | | | | | | | |
-10 | -12| -14| -17| -20| -23| -27| -33| -42| -58| | | | | -10
-9 | -11| -13| -15| -18| -21| -25| -30| -37| -48| | | | | -9
-8 | -10| -12| -14| -17| -20| -23| -27| -33| -42| -58| | | | -8
-7 | -9| -11| -13| -15| -18| -21| -25| -30| -36| -48| | | | -7
-6 | -8| -10| -12| -14| -16| -19| -23| -27| -32| -41| -56| | | -6
| | | | | | | | | | | | | |
-5 | -7| -8| -10| -12| -15| -17| -21| -24| -29| -35| -47| | | -5
-4 | -6| -7| -9| -11| -13| -16| -19| -22| -26| -31| -39| -54| | -4
-3 | -4| -6| -8| -10| -12| -14| -17| -20| -23| -28| -33| -44| | -3
-2 | -3| -5| -6| -8| -10| -12| -15| -18| -21| -24| -29| -36| -48| -2
-1 | -2| -4| -5| -7| -9| -11| -13| -16| -18| -22| -26| -31| -39| -1
| | | | | | | | | | | | | |
±0 | -1| -3| -4| -6| -7| -9| -11| -14| -16| -19| -23| -27| -33| 0
+1 | -0| -2| -3| -4| -6| -8| -10| -12| -14| -17| -20| -24| -28| +1
2 | +1| -1| -2| -3| -5| -6| -8| -10| -12| -15| -17| -21| -25| 2
3 | 2| +1| -1| -2| -3| -5| -7| -8| -10| -13| -15| -18| -21| 3
4 | 3| +2| 0| -1| -2| -4| -5| -7| -9| -11| -13| -16| -19| 4
| | | | | | | | | | | | | |
5 | 4| 3| +1| 0| -1| -2| -4| -5| -7| -9| -11| -14| -16| 5
6 | 5| 4| 3| +1| 0| -1| -3| -4| -6| -7| -9| -12| -14| 6
7 | 6| 5| 4| 3| +1| 0| -1| -3| -4| -6| -8| -10| -12| 7
8 | 7| 6| 5| 4| 3| +1| 0| -1| -3| -4| -6| -8| -10| 8
9 | 8| 7| 6| 5| 4| 3| +1| 0| -1| -3| -4| -6| -8| 9
| | | | | | | | | | | | | |
10 | 9| 8| 7| 6| 5| 4| 3| +1| 0| -1| -3| -4| -6| 10
11 | 10| 9| 8| 7| 6| 5| 4| 3| +2| 0| -1| -3| -4| 11
12 | 11| 10| 9| 9| 8| 7| 5| 4| 3| +2| 0| -1| -2| 12
13 | 12| 11| 11| 10| 9| 8| 7| 6| 5| 3| +2| +1| -1| 13
14 | 13| 12| 12| 11| 10| 9| 8| 7| 6| 5| 4| 2| +1| 14
| | | | | | | | | | | | | |
15 | 14| 13| 13| 12| 11| 10| 9| 8| 7| 6| 5| 4| 3| 15
16 | 15| 15| 14| 13| 12| 11| 10| 10| 9| 8| 7| 5| 4| 16
17 | 16| 16| 15| 14| 13| 12| 12| 11| 10| 9| 8| 7| 6| 17
18 | 17| 17| 16| 15| 14| 14| 13| 12| 11| 10| 9| 8| 7| 18
19 | 18| 18| 17| 16| 15| 15| 14| 13| 12| 11| 10| 10| 9| 19
| | | | | | | | | | | | | |
20 | 19| 19| 18| 17| 17| 16| 15| 14| 13| 13| 12| 11| 10| 20
------+----+----+----+----+----+----+----+----+----+----+----+----+----+ ——————
_t._ |0°.2|0°.4|0°.6|0°.8|1°.0|1°.2|1°.4|1°.6|1°.8|2°.0|2°.2|2°.4|2°.6| _t._
======+====+====+====+====+====+====+====+====+====+====+====+====+====+======
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+===========================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+(Dry
ther.)| 2°.6| 2°.8| 3°.0| 3°.2| 3°.4| 3°.6| 3°.8| 4°.0| 4°.2| 4°.4|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
-2 | -48 | | | | | | | | | | -2
-1 | -39 | -54 | | | | | | | | | -1
| | | | | | | | | | |
0 | -33 | -43 | | | | | | | | | 0
+1 | -28 | -35 | -46 | | | | | | | | +1
2 | -25 | -30 | -37 | -50 | | | | | | | 2
3 | -21 | -26 | -31 | -39 | -54 | | | | | | 3
4 | -19 | -22 | -27 | -32 | -42 | -60 | | | | | 4
| | | | | | | | | | |
5 | -16 | -19 | -23 | -28 | -34 | -45 | | | | | 5
6 | -14 | -17 | -20 | -24 | -29 | -35 | -47 | | | | 6
7 | -12 | -14 | -17 | -20 | -24 | -29 | -37 | -50 | | | 7
8 | -10 | -12 | -15 | -17 | -21 | -25 | -30 | -38 | -53 | | 8
9 | -8 | -10 | -12 | -15 | -18 | -21 | -25 | -31 | -39 | -55 | 9
| | | | | | | | | | |
10 | -6 | -8 | -10 | -12 | -15 | -18 | -21 | -26 | -31 | -40 | 10
11 | -4 | -6 | -8 | -10 | -12 | -15 | -18 | -21 | -26 | -31 | 11
12 | -2 | -4 | -6 | -8 | -10 | -12 | -15 | -18 | -21 | -26 | 12
13 | -1 | -2 | -4 | -5 | -7 | -9 | -12 | -14 | -17 | -21 | 13
14 | +1 | 0 | -2 | -3 | -5 | -7 | -9 | -11 | -14 | -17 | 14
| | | | | | | | | | |
15 | 3 | +1 | 0 | -2 | -3 | -5 | -7 | -9 | -11 | -14 | 15
16 | 4 | 3 | +2 | 0 | -1 | -3 | -4 | -6 | -8 | -10 | 16
17 | 6 | 5 | 3 | +2 | +1 | -1 | -2 | -4 | -6 | -8 | 17
18 | 7 | 6 | 5 | 4 | 2 | +1 | 0 | -2 | -3 | -5 | 18
19 | 9 | 8 | 7 | 5 | 4 | 3 | +1 | 0 | -1 | -3 | 19
| | | | | | | | | | |
20 | 10 | 9 | 8 | 7 | 6 | 5 | 3 | +2 | +1 | -1 | 20
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ | 2°.6| 2°.8| 3°.0| 3°.2| 3°.4| 3°.6| 3°.8| 4°.0| 4°.2| 4°.4| _t._
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
_t._ | 4°.6| 4°.8| 5°.0| 5°.2| 5°.4| 5°.6| 5°.8| 6°.0| 6°.2| 6°.4| _t._
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
8 | | | | | | | | | | | 8
9 | | | | | | | | | | | 9
| | | | | | | | | | |
10 | -57 | | | | | | | | | | 10
11 | -41 | -60 | | | | | | | | | 11
12 | -31 | -41 | -59 | | | | | | | | 12
13 | -25 | -31 | -40 | -58 | | | | | | | 13
14 | -20 | -25 | -30 | -39 | -56 | | | | | | 14
| | | | | | | | | | |
15 | -16 | -20 | -24 | -30 | -38 | -53 | | | | | 15
16 | -13 | -16 | -19 | -23 | -28 | -36 | -50 | | | | 16
17 | -10 | -12 | -15 | -18 | -22 | -27 | -34 | -47 | | | 17
18 | -7 | -9 | -12 | -14 | -17 | -21 | -26 | -32 | -44 | | 18
19 | -5 | -7 | -9 | -11 | -14 | -17 | -20 | -25 | -30 | -40 | 19
| | | | | | | | | | |
20 | -2 | -4 | -6 | -8 | -10 | -13 | -16 | -19 | -23 | -29 | 20
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ | 4°.6| 4°.8| 5°.0| 5°.2| 5°.4| 5°.6| 5°.8| 6°.0| 6°.2| 6°.4| _t_.
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+===========================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +----+----+----+----+----+----+----+----+----+----+----+----+(Dry
ther.)|0°.5|1°.0|1°.5|2°.0|2°.5|3°.0|3°.5|4°.0|4°.5|5°.0|5°.5|6°.0|ther.)
------+----+----+----+----+----+----+----+----+----+----+----+----+------
20 | 18 | 17 | 15 | 13 | 10 | 8 | 5 | 2 | -2 | -6 |-12 |-19 | 20
21 | 19 | 18 | 16 | 14 | 12 | 9 | 7 | 4 | 0 | -4 | -8 |-15 | 21
22 | 20 | 19 | 17 | 15 | 13 | 11 | 8 | 6 | +2 | -1 | -6 |-11 | 22
23 | 22 | 20 | 18 | 16 | 14 | 12 | 10 | 7 | 4 | +1 | -3 | -8 | 23
24 | 23 | 21 | 19 | 18 | 16 | 14 | 11 | 9 | 6 | 3 | -1 | -5 | 24
| | | | | | | | | | | | |
25 | 24 | 22 | 21 | 19 | 17 | 15 | 13 | 11 | 8 | 5 | +2 | -2 | 25
26 | 25 | 23 | 22 | 20 | 18 | 16 | 14 | 12 | 10 | 7 | 4 | 0 | 26
27 | 26 | 24 | 23 | 21 | 20 | 18 | 16 | 14 | 11 | 9 | 6 | +3 | 27
28 | 27 | 25 | 24 | 22 | 21 | 19 | 17 | 15 | 13 | 11 | 8 | 5 | 28
29 | 28 | 26 | 25 | 24 | 22 | 20 | 19 | 17 | 14 | 12 | 10 | 7 | 29
| | | | | | | | | | | | |
30 | 29 | 27 | 26 | 25 | 23 | 22 | 20 | 18 | 16 | 14 | 11 | 9 | 30
31 | 30 | 29 | 27 | 26 | 24 | 23 | 21 | 19 | 18 | 15 | 13 | 11 | 31
32 | 31 | 30 | 28 | 27 | 26 | 24 | 22 | 21 | 19 | 17 | 15 | 13 | 32
33 | 31 | 31 | 29 | 28 | 26 | 25 | 23 | 22 | 19 | 18 | 16 | 14 | 33
34 | 32 | 32 | 30 | 29 | 27 | 26 | 24 | 24 | 21 | 20 | 18 | 16 | 34
| | | | | | | | | | | | |
35 | 33 | 32 | 31 | 30 | 29 | 28 | 26 | 25 | 23 | 22 | 20 | 18 | 35
36 | 35 | 34 | 32 | 31 | 30 | 29 | 27 | 26 | 24 | 23 | 21 | 19 | 36
37 | 36 | 35 | 33 | 32 | 31 | 30 | 28 | 27 | 26 | 24 | 22 | 21 | 37
38 | 37 | 36 | 34 | 33 | 32 | 31 | 30 | 28 | 27 | 26 | 24 | 22 | 38
39 | 38 | 37 | 35 | 34 | 33 | 32 | 30 | 29 | 28 | 27 | 25 | 24 | 39
| | | | | | | | | | | | |
40 | 39 | 38 | 36 | 35 | 34 | 33 | 31 | 30 | 29 | 28 | 26 | 25 | 40
41 | 40 | 39 | 37 | 36 | 35 | 34 | 32 | 32 | 30 | 29 | 28 | 26 | 41
42 | 41 | 40 | 39 | 38 | 36 | 35 | 34 | 33 | 31 | 30 | 29 | 27 | 42
43 | 42 | 41 | 40 | 39 | 37 | 36 | 35 | 34 | 32 | 31 | 30 | 29 | 43
44 | 43 | 42 | 41 | 40 | 38 | 37 | 36 | 35 | 33 | 32 | 31 | 30 | 44
| | | | | | | | | | | | |
45 | 44 | 43 | 42 | 41 | 40 | 39 | 37 | 36 | 34 | 33 | 32 | 31 | 45
46 | 45 | 44 | 43 | 42 | 41 | 40 | 38 | 37 | 36 | 35 | 33 | 32 | 46
47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 39 | 37 | 36 | 34 | 33 | 47
48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 38 | 37 | 36 | 35 | 48
49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 39 | 38 | 37 | 36 | 49
| | | | | | | | | | | | |
50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 38 | 37 | 50
51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 39 | 38 | 51
52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 52
53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 53
54 | 53 | 52 | 51 | 50 | 50 | 49 | 47 | 46 | 45 | 44 | 43 | 42 | 54
| | | | | | | | | | | | |
55 | 54 | 53 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 44 | 43 | 55
56 | 55 | 54 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 45 | 44 | 56
57 | 56 | 55 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 57
58 | 57 | 56 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 58
59 | 58 | 57 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 59
| | | | | | | | | | | | |
60 | 59 | 58 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 60
61 | 60 | 59 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 61
62 | 61 | 60 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 52 | 62
63 | 62 | 61 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 55 | 54 | 53 | 63
64 | 63 | 62 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 56 | 55 | 54 | 64
| | | | | | | | | | | | |
65 | 64 | 63 | 63 | 62 | 61 | 60 | 59 | 59 | 58 | 57 | 56 | 55 | 65
66 | 65 | 64 | 64 | 63 | 62 | 61 | 60 | 60 | 59 | 58 | 57 | 56 | 66
67 | 67 | 66 | 65 | 64 | 63 | 62 | 61 | 61 | 60 | 59 | 58 | 57 | 67
68 | 68 | 67 | 66 | 65 | 64 | 63 | 62 | 62 | 61 | 60 | 59 | 58 | 68
69 | 69 | 68 | 67 | 66 | 65 | 64 | 63 | 63 | 62 | 61 | 60 | 59 | 69
| | | | | | | | | | | | |
70 | 70 | 69 | 68 | 67 | 67 | 66 | 65 | 64 | 63 | 62 | 61 | 61 | 70
71 | 71 | 70 | 69 | 68 | 68 | 67 | 66 | 65 | 64 | 63 | 62 | 62 | 71
72 | 72 | 71 | 70 | 69 | 69 | 68 | 67 | 66 | 65 | 64 | 63 | 63 | 72
73 | 73 | 72 | 71 | 70 | 70 | 69 | 68 | 67 | 66 | 66 | 65 | 64 | 73
74 | 74 | 73 | 72 | 71 | 71 | 70 | 69 | 68 | 67 | 67 | 66 | 65 | 74
| | | | | | | | | | | | |
75 | 75 | 74 | 73 | 72 | 72 | 71 | 70 | 69 | 68 | 68 | 67 | 66 | 75
76 | 76 | 75 | 74 | 73 | 73 | 72 | 71 | 70 | 69 | 69 | 68 | 67 | 76
77 | 77 | 76 | 75 | 74 | 74 | 73 | 72 | 71 | 70 | 70 | 69 | 68 | 77
78 | 78 | 77 | 76 | 75 | 75 | 74 | 73 | 72 | 71 | 71 | 70 | 69 | 78
79 | 79 | 78 | 77 | 76 | 76 | 75 | 74 | 73 | 72 | 72 | 71 | 70 | 79
| | | | | | | | | | | | |
80 | 80 | 79 | 78 | 77 | 77 | 76 | 75 | 74 | 73 | 73 | 72 | 72 | 80
------+----+----+----+----+----+----+----+----+----+----+----+----+------
_t._ |0°.5|1°.0|1°.5|2°.0|2°.5|3°.0|3°.5|4°.0|4°.5|5°.0|5°.5|6°.0| _t._
======+====+====+====+====+====+====+====+====+====+====+====+====+======
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+=============================================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ (Dry
ther.)| 6°.0| 6°.5| 7°.0| 7°.5| 8°.0| 8°.5| 9°.0| 9°.5|10°.0|10°.5|11°.0|11°.5|12°.0|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
19 | -25 | | | | | | | | | | | | | 19
| | | | | | | | | | | | | |
20 | -19 | -32 | | | | | | | | | | | | 20
21 | -15 | -24 | -47 | | | | | | | | | | | 21
22 | -11 | -19 | -31 | | | | | | | | | | | 22
23 | -8 | -14 | -24 | -45 | | | | | | | | | | 23
24 | -5 | -10 | -18 | -30 | | | | | | | | | | 24
| | | | | | | | | | | | | |
25 | -2 | -7 | -13 | -22 | -42 | | | | | | | | | 25
26 | 0 | -4 | -9 | -17 | -28 | | | | | | | | | 26
27 | +3 | -1 | -6 | -12 | -20 | -37 | | | | | | | | 27
28 | 5 | +1 | -3 | -8 | -15 | -25 | -54 | | | | | | | 28
29 | 7 | 4 | 0 | -4 | -10 | -18 | -32 | | | | | | | 29
| | | | | | | | | | | | | |
30 | 9 | 6 | +2 | -2 | -6 | -13 | -22 | -43 | | | | | | 30
31 | 11 | 8 | 5 | +1 | -3 | -8 | -15 | -27 | | | | | | 31
32 | 13 | 10 | 7 | 4 | 0 | -4 | -10 | -18 | -33 | | | | | 32
33 | 14 | 12 | 9 | 6 | +3 | -1 | -6 | -12 | -22 | -44 | | | | 33
34 | 16 | 14 | 11 | 8 | 6 | +2 | -2 | -8 | -15 | -27 | | | | 34
| | | | | | | | | | | | | |
35 | 18 | 15 | 13 | 10 | 8 | 5 | +1 | -4 | -9 | -18 | -32 | | | 35
36 | 19 | 17 | 15 | 12 | 10 | 8 | 4 | 0 | -5 | -12 | -20 | -42 | | 36
37 | 21 | 19 | 17 | 14 | 12 | 9 | 6 | +3 | -2 | -6 | -14 | -25 | -52 | 37
38 | 22 | 20 | 19 | 16 | 14 | 11 | 9 | 6 | +2 | -2 | -8 | -16 | -29 | 38
39 | 24 | 22 | 20 | 18 | 16 | 14 | 11 | 8 | 5 | +1 | -4 | -10 | -18 | 39
| | | | | | | | | | | | | |
40 | 25 | 23 | 22 | 20 | 18 | 16 | 13 | 11 | 8 | 4 | 0 | -5 | -12 | 40
41 | 26 | 25 | 23 | 21 | 20 | 17 | 15 | 13 | 10 | 7 | +4 | -1 | -6 | 41
42 | 27 | 26 | 24 | 23 | 21 | 19 | 18 | 15 | 12 | 10 | 7 | +3 | -2 | 42
43 | 29 | 27 | 26 | 24 | 23 | 21 | 19 | 17 | 14 | 12 | 9 | 6 | +2 | 43
44 | 30 | 28 | 27 | 26 | 24 | 22 | 20 | 18 | 16 | 14 | 12 | 9 | 6 | 44
| | | | | | | | | | | | | |
45 | 31 | 30 | 28 | 27 | 25 | 24 | 22 | 20 | 18 | 16 | 13 | 11 | 8 | 45
46 | 32 | 31 | 30 | 28 | 27 | 25 | 24 | 22 | 20 | 18 | 16 | 13 | 11 | 46
47 | 33 | 32 | 31 | 29 | 28 | 26 | 25 | 23 | 22 | 20 | 18 | 15 | 13 | 47
48 | 35 | 33 | 32 | 30 | 29 | 28 | 26 | 25 | 23 | 21 | 20 | 17 | 15 | 48
49 | 36 | 34 | 33 | 32 | 31 | 29 | 28 | 26 | 25 | 23 | 21 | 19 | 17 | 49
| | | | | | | | | | | | | |
50 | 37 | 35 | 34 | 33 | 32 | 31 | 29 | 28 | 26 | 24 | 23 | 21 | 19 | 50
51 | 38 | 37 | 36 | 34 | 33 | 32 | 31 | 29 | 28 | 26 | 24 | 22 | 21 | 51
52 | 40 | 38 | 37 | 36 | 34 | 33 | 32 | 30 | 29 | 28 | 26 | 24 | 23 | 52
53 | 41 | 39 | 38 | 37 | 36 | 34 | 33 | 32 | 30 | 29 | 28 | 26 | 24 | 53
54 | 42 | 41 | 40 | 39 | 37 | 36 | 34 | 33 | 32 | 30 | 29 | 27 | 26 | 54
| | | | | | | | | | | | | |
55 | 43 | 42 | 41 | 40 | 39 | 37 | 36 | 34 | 33 | 32 | 30 | 29 | 28 | 55
56 | 44 | 43 | 42 | 41 | 40 | 39 | 37 | 36 | 34 | 33 | 32 | 30 | 29 | 56
57 | 46 | 45 | 44 | 42 | 41 | 40 | 39 | 37 | 36 | 35 | 33 | 32 | 30 | 57
58 | 47 | 46 | 45 | 44 | 42 | 41 | 40 | 39 | 37 | 36 | 35 | 33 | 32 | 58
59 | 48 | 47 | 46 | 45 | 44 | 43 | 41 | 40 | 39 | 38 | 36 | 35 | 33 | 59
| | | | | | | | | | | | | |
60 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 41 | 40 | 39 | 38 | 36 | 35 | 60
61 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 39 | 38 | 36 | 61
62 | 52 | 51 | 50 | 49 | 48 | 47 | 45 | 44 | 43 | 42 | 41 | 39 | 38 | 62
63 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 45 | 44 | 43 | 42 | 41 | 39 | 63
64 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 43 | 42 | 41 | 64
| | | | | | | | | | | | | |
65 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 43 | 42 | 65
66 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 66
67 | 57 | 56 | 55 | 55 | 54 | 53 | 52 | 51 | 50 | 48 | 47 | 46 | 45 | 67
68 | 58 | 57 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 47 | 46 | 68
69 | 59 | 58 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 69
| | | | | | | | | | | | | |
70 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 70
71 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 55 | 54 | 53 | 52 | 51 | 71
72 | 63 | 62 | 61 | 60 | 59 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 72
73 | 64 | 63 | 62 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 73
74 | 65 | 64 | 63 | 63 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 74
| | | | | | | | | | | | | |
75 | 66 | 65 | 64 | 64 | 63 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 56 | 75
76 | 67 | 66 | 65 | 65 | 64 | 63 | 62 | 61 | 61 | 60 | 59 | 58 | 57 | 76
77 | 68 | 67 | 67 | 66 | 65 | 64 | 63 | 62 | 62 | 61 | 60 | 59 | 58 | 77
78 | 69 | 68 | 68 | 67 | 66 | 66 | 65 | 64 | 63 | 62 | 61 | 60 | 59 | 78
79 | 70 | 69 | 69 | 68 | 67 | 67 | 66 | 65 | 64 | 63 | 62 | 61 | 61 | 79
| | | | | | | | | | | | | |
80 | 72 | 71 | 70 | 69 | 68 | 68 | 67 | 66 | 65 | 64 | 63 | 62 | 62 | 80
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ | 6°.0| 6°.5| 7°.0| 7°.5| 8°.0| 8°.5| 9°.0| 9°.5|10°.0|10°.5|11°.0|11°.5|12°.0| _t._
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+=============================================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+(Dry
ther.)|12°.0|12°.5|13°.0|13°.5|14°.0|14°.5|15°.0|15°.5|16°.0|16°.5|17°.0|17°.5|18°.0|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
40 | -12 | -22 | -44 | | | | | | | | | | | 40
41 | -6 | -13 | -25 | | | | | | | | | | | 41
42 | -2 | -7 | -15 | -28 | | | | | | | | | | 42
43 | +2 | -3 | -8 | -17 | -33 | | | | | | | | | 43
44 | 6 | +1 | -4 | -10 | -19 | -40 | | | | | | | | 44
| | | | | | | | | | | | | |
45 | 8 | 5 | 0 | -4 | -11 | -22 | -48 | | | | | | | 45
46 | 11 | 8 | +4 | 0 | -5 | -13 | -24 | | | | | | | 46
47 | 13 | 10 | 7 | +3 | -1 | -6 | -14 | -27 | | | | | | 47
48 | 15 | 12 | 10 | 6 | +2 | -2 | -8 | -16 | -30 | | | | | 48
49 | 17 | 14 | 12 | 9 | 6 | +2 | -3 | -9 | -18 | -35 | | | | 49
| | | | | | | | | | | | | |
50 | 19 | 16 | 14 | 12 | 9 | 5 | +1 | -4 | -10 | -20 | -42 | | | 50
51 | 21 | 18 | 17 | 14 | 11 | 8 | 5 | 0 | -5 | -12 | -22 | -52 | | 51
52 | 23 | 21 | 19 | 16 | 14 | 11 | 8 | +4 | 0 | -6 | -13 | -25 | | 52
53 | 24 | 22 | 20 | 18 | 16 | 14 | 11 | 8 | +4 | -1 | -6 | -14 | -28 | 53
54 | 26 | 24 | 22 | 20 | 18 | 16 | 13 | 10 | 7 | +3 | -2 | -8 | -16 | 54
| | | | | | | | | | | | | |
55 | 28 | 26 | 24 | 22 | 20 | 18 | 16 | 13 | 10 | 7 | +3 | -2 | -8 | 55
56 | 29 | 27 | 26 | 24 | 22 | 20 | 18 | 15 | 13 | 10 | 6 | +2 | -2 | 56
57 | 30 | 29 | 28 | 26 | 24 | 22 | 20 | 18 | 15 | 13 | 10 | 6 | +2 | 57
58 | 32 | 30 | 29 | 27 | 26 | 24 | 22 | 20 | 18 | 15 | 12 | 9 | 6 | 58
59 | 33 | 32 | 31 | 29 | 27 | 26 | 24 | 22 | 20 | 18 | 15 | 12 | 9 | 59
| | | | | | | | | | | | | |
60 | 35 | 33 | 32 | 30 | 29 | 27 | 26 | 24 | 22 | 20 | 18 | 15 | 12 | 60
61 | 36 | 35 | 33 | 32 | 31 | 29 | 28 | 26 | 24 | 22 | 20 | 18 | 15 | 61
62 | 38 | 37 | 35 | 34 | 32 | 31 | 29 | 28 | 26 | 24 | 22 | 20 | 18 | 62
63 | 39 | 38 | 37 | 35 | 34 | 32 | 31 | 29 | 28 | 26 | 24 | 22 | 20 | 63
64 | 41 | 39 | 38 | 37 | 35 | 34 | 32 | 31 | 29 | 28 | 26 | 24 | 22 | 64
| | | | | | | | | | | | | |
65 | 42 | 41 | 40 | 38 | 37 | 35 | 34 | 32 | 31 | 29 | 28 | 26 | 24 | 65
66 | 44 | 43 | 41 | 40 | 38 | 37 | 35 | 34 | 32 | 31 | 30 | 28 | 26 | 66
67 | 45 | 44 | 43 | 41 | 40 | 39 | 37 | 36 | 34 | 32 | 31 | 30 | 28 | 67
68 | 46 | 45 | 44 | 43 | 42 | 40 | 39 | 38 | 36 | 34 | 33 | 31 | 30 | 68
69 | 48 | 47 | 46 | 45 | 43 | 42 | 40 | 39 | 38 | 36 | 34 | 33 | 32 | 69
| | | | | | | | | | | | | |
70 | 49 | 48 | 47 | 46 | 45 | 43 | 42 | 41 | 39 | 38 | 36 | 35 | 33 | 70
71 | 51 | 49 | 48 | 47 | 46 | 45 | 43 | 42 | 41 | 39 | 38 | 36 | 35 | 71
72 | 52 | 51 | 50 | 49 | 47 | 46 | 45 | 44 | 43 | 41 | 40 | 38 | 37 | 72
73 | 53 | 52 | 51 | 50 | 49 | 48 | 46 | 45 | 44 | 43 | 41 | 40 | 38 | 73
74 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 45 | 44 | 43 | 41 | 40 | 74
| | | | | | | | | | | | | |
75 | 56 | 55 | 54 | 53 | 52 | 50 | 49 | 48 | 47 | 45 | 44 | 43 | 42 | 75
76 | 57 | 56 | 55 | 54 | 53 | 52 | 50 | 49 | 48 | 47 | 46 | 45 | 43 | 76
77 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 46 | 45 | 77
78 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 78
79 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 49 | 48 | 79
| | | | | | | | | | | | | |
80 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 80
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ |12°.0|12°.5|13°.0|13°.5|14°.0|14°.5|15°.0|15°.5|16°.0|16°.5|17°.0|17°.5|18°.0| _t._
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+=============================================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+(Dry
ther.)|18°.0|19°.0|20°.0|21°.0|22°.0|23°.0|24°.0|25°.0|26°.0|27°.0|28°.0|29°.0|30°.0|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
55 | -8 | | | | | | | | | | | | | 55
56 | -2 | -19 | | | | | | | | | | | | 56
57 | +2 | -10 | -48 | | | | | | | | | | | 57
58 | 6 | -3 | -22 | | | | | | | | | | | 58
59 | 9 | +1 | -12 | | | | | | | | | | | 59
| | | | | | | | | | | | | |
60 | 12 | 5 | -5 | -25 | | | | | | | | | | 60
61 | 15 | 9 | 0 | -14 | | | | | | | | | | 61
62 | 18 | 12 | +5 | -6 | -28 | | | | | | | | | 62
63 | 20 | 15 | 9 | 0 | -14 | | | | | | | | | 63
64 | 22 | 18 | 12 | +4 | -6 | -32 | | | | | | | | 64
| | | | | | | | | | | | | |
65 | 24 | 20 | 15 | 9 | 0 | -16 | | | | | | | | 65
66 | 26 | 22 | 18 | 12 | +4 | -7 | -34 | | | | | | | 66
67 | 28 | 24 | 20 | 15 | 9 | -1 | -16 | | | | | | | 67
68 | 30 | 26 | 23 | 18 | 12 | +4 | -7 | -37 | | | | | | 68
69 | 32 | 28 | 25 | 20 | 15 | 8 | 0 | -17 | | | | | | 69
| | | | | | | | | | | | | |
70 | 33 | 30 | 27 | 23 | 19 | 12 | +5 | -7 | -39 | | | | | 70
71 | 35 | 32 | 29 | 25 | 21 | 16 | 9 | 0 | -17 | | | | | 71
72 | 37 | 33 | 31 | 27 | 23 | 18 | 13 | +5 | -6 | -39 | | | | 72
73 | 38 | 35 | 32 | 29 | 25 | 21 | 16 | 10 | 0 | -16 | | | | 73
74 | 40 | 37 | 34 | 31 | 28 | 24 | 19 | 13 | +6 | -6 | -37 | | | 74
| | | | | | | | | | | | | |
75 | 42 | 39 | 36 | 32 | 30 | 26 | 22 | 16 | 10 | 0 | -16 | | | 75
76 | 43 | 41 | 38 | 34 | 32 | 28 | 24 | 20 | 14 | +6 | -6 | -34 | | 76
77 | 45 | 42 | 40 | 36 | 33 | 30 | 26 | 22 | 17 | 11 | +1 | -14 | | 77
78 | 47 | 44 | 41 | 38 | 35 | 32 | 28 | 24 | 20 | 14 | 7 | -4 | -30 | 78
79 | 48 | 46 | 43 | 40 | 37 | 34 | 31 | 27 | 23 | 18 | 11 | +2 | -13 | 79
| | | | | | | | | | | | | |
80 | 50 | 47 | 45 | 42 | 39 | 36 | 32 | 29 | 25 | 21 | 15 | 8 | -3 | 80
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t_ |18°.0|19°.0|20°.0|21°.0|22°.0|23°.0|24°.0|25°.0|26°.0|27°.0|28°.0|29°.0|30°.0| _t_
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+==============================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +----+----+----+----+----+----+----+----+----+-----+-----+-----+(Dry
ther.)|1°.0|2°.0|3°.0|4°.0|5°.0|6°.0|7°.0|8°.0|9°.0|10°.0|11°.0|12°.0|ther.)
------+----+----+----+----+----+----+----+----+----+-----+-----+-----+------
80 | 79 | 77 | 76 | 74 | 73 | 72 | 70 | 68 | 67 | 65 | 63 | 62 | 80
81 | 80 | 78 | 77 | 75 | 74 | 73 | 71 | 70 | 68 | 66 | 65 | 63 | 81
82 | 81 | 79 | 78 | 77 | 75 | 74 | 72 | 71 | 69 | 68 | 66 | 64 | 82
83 | 82 | 80 | 79 | 78 | 76 | 75 | 73 | 72 | 70 | 69 | 67 | 65 | 83
84 | 83 | 81 | 80 | 79 | 77 | 76 | 74 | 73 | 71 | 70 | 68 | 67 | 84
| | | | | | | | | | | | |
85 | 84 | 82 | 81 | 80 | 78 | 77 | 75 | 74 | 72 | 71 | 69 | 68 | 85
86 | 85 | 83 | 82 | 81 | 79 | 78 | 76 | 75 | 73 | 72 | 71 | 69 | 86
87 | 86 | 84 | 83 | 82 | 80 | 79 | 78 | 76 | 74 | 73 | 72 | 70 | 87
88 | 87 | 85 | 84 | 83 | 81 | 80 | 79 | 77 | 75 | 74 | 73 | 71 | 88
89 | 88 | 86 | 85 | 84 | 82 | 81 | 80 | 78 | 76 | 76 | 74 | 72 | 89
| | | | | | | | | | | | |
90 | 89 | 87 | 86 | 85 | 84 | 82 | 81 | 79 | 78 | 77 | 75 | 74 | 90
91 | 90 | 88 | 87 | 86 | 85 | 83 | 82 | 80 | 79 | 78 | 76 | 75 | 91
92 | 91 | 89 | 88 | 87 | 86 | 84 | 83 | 82 | 80 | 79 | 77 | 76 | 92
93 | 92 | 91 | 89 | 88 | 87 | 85 | 84 | 83 | 81 | 80 | 78 | 77 | 93
94 | 93 | 92 | 90 | 89 | 88 | 86 | 85 | 84 | 82 | 81 | 80 | 78 | 94
| | | | | | | | | | | | |
95 | 94 | 93 | 91 | 90 | 89 | 87 | 86 | 85 | 83 | 82 | 81 | 79 | 95
96 | 95 | 94 | 92 | 91 | 90 | 88 | 87 | 86 | 84 | 83 | 82 | 80 | 96
97 | 96 | 95 | 93 | 92 | 91 | 90 | 88 | 87 | 86 | 84 | 83 | 81 | 97
98 | 97 | 96 | 94 | 93 | 92 | 91 | 89 | 88 | 87 | 85 | 84 | 83 | 98
99 | 98 | 97 | 95 | 94 | 93 | 92 | 90 | 89 | 88 | 86 | 85 | 84 | 99
| | | | | | | | | | | | |
100 | 99 | 98 | 96 | 95 | 94 | 93 | 91 | 90 | 89 | 87 | 86 | 85 | 100
101 |100 | 99 | 97 | 96 | 95 | 94 | 92 | 91 | 90 | 88 | 87 | 86 | 101
102 |101 |100 | 98 | 97 | 96 | 95 | 93 | 92 | 91 | 90 | 88 | 87 | 102
103 |102 |101 | 99 | 98 | 97 | 96 | 94 | 93 | 92 | 91 | 89 | 88 | 103
104 |103 |102 |100 | 99 | 98 | 97 | 96 | 94 | 93 | 92 | 90 | 89 | 104
| | | | | | | | | | | | |
105 |104 |103 |101 |100 | 99 | 98 | 97 | 95 | 94 | 93 | 91 | 90 | 105
106 |105 |104 |102 |101 |100 | 99 | 98 | 96 | 95 | 94 | 93 | 91 | 106
107 |106 |105 |103 |102 |101 |100 | 99 | 97 | 96 | 95 | 94 | 92 | 107
108 |107 |106 |104 |103 |102 |101 |100 | 98 | 97 | 96 | 95 | 93 | 108
109 |108 |107 |105 |104 |103 |102 |101 | 99 | 98 | 97 | 96 | 94 | 109
| | | | | | | | | | | | |
110 |109 |108 |107 |105 |104 |103 |102 |101 | 99 | 98 | 97 | 96 | 110
------+----+----+----+----+----+----+----+----+----+-----+-----+-----+------
_t._ |1°.0|2°.0|3°.0|4°.0|5°.0|6°.0|7°.0|8°.0|9°.0|10°.0|11°.0|12°.0| _t._
======+====+====+====+====+====+====+====+====+====+=====+=====+=====+======
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+=============================================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+(Dry
ther.)|12°.0|13°.0|14°.0|15°.0|16°.0|17°.0|18°.0|19°.0|20°.0|21°.0|22°.0|23°.0|24°.0|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
80 | 62 | 60 | 58 | 56 | 54 | 52 | 50 | 47 | 45 | 42 | 39 | 36 | 32 | 80
81 | 63 | 61 | 59 | 57 | 55 | 53 | 51 | 49 | 47 | 44 | 41 | 38 | 35 | 81
82 | 64 | 62 | 61 | 59 | 57 | 55 | 53 | 50 | 48 | 45 | 43 | 40 | 37 | 82
83 | 65 | 64 | 62 | 60 | 58 | 56 | 54 | 52 | 50 | 47 | 44 | 42 | 39 | 83
84 | 67 | 65 | 63 | 61 | 59 | 57 | 55 | 53 | 51 | 49 | 46 | 43 | 41 | 84
| | | | | | | | | | | | | |
85 | 68 | 66 | 64 | 62 | 61 | 59 | 57 | 55 | 53 | 50 | 48 | 45 | 42 | 85
86 | 69 | 67 | 66 | 64 | 62 | 60 | 58 | 56 | 54 | 52 | 49 | 47 | 44 | 86
87 | 70 | 68 | 67 | 65 | 63 | 61 | 59 | 57 | 55 | 53 | 51 | 48 | 46 | 87
88 | 71 | 70 | 68 | 66 | 64 | 63 | 61 | 59 | 57 | 55 | 53 | 50 | 48 | 88
89 | 72 | 71 | 69 | 67 | 66 | 64 | 62 | 60 | 58 | 56 | 54 | 52 | 49 | 89
| | | | | | | | | | | | | |
90 | 74 | 72 | 70 | 69 | 67 | 65 | 63 | 62 | 60 | 58 | 56 | 53 | 51 | 90
91 | 75 | 73 | 72 | 70 | 68 | 67 | 65 | 63 | 61 | 59 | 57 | 55 | 53 | 91
92 | 76 | 74 | 73 | 71 | 69 | 68 | 66 | 64 | 62 | 60 | 58 | 56 | 54 | 92
93 | 77 | 75 | 74 | 72 | 71 | 69 | 67 | 66 | 64 | 62 | 60 | 58 | 56 | 93
94 | 78 | 77 | 75 | 73 | 72 | 70 | 69 | 67 | 65 | 63 | 61 | 59 | 57 | 94
| | | | | | | | | | | | | |
95 | 79 | 78 | 76 | 75 | 73 | 71 | 70 | 68 | 66 | 64 | 63 | 61 | 59 | 95
96 | 80 | 79 | 77 | 76 | 74 | 73 | 71 | 69 | 68 | 66 | 64 | 62 | 60 | 96
97 | 81 | 80 | 78 | 77 | 75 | 74 | 72 | 71 | 69 | 67 | 65 | 63 | 61 | 97
98 | 83 | 81 | 80 | 78 | 77 | 75 | 73 | 72 | 70 | 68 | 67 | 65 | 63 | 98
99 | 84 | 82 | 81 | 79 | 78 | 76 | 75 | 73 | 71 | 70 | 68 | 66 | 64 | 99
| | | | | | | | | | | | | |
100 | 85 | 83 | 82 | 80 | 79 | 77 | 76 | 74 | 73 | 71 | 69 | 67 | 66 | 100
101 | 86 | 84 | 83 | 82 | 80 | 79 | 77 | 75 | 74 | 72 | 71 | 69 | 67 | 101
102 | 87 | 85 | 84 | 83 | 81 | 80 | 78 | 77 | 75 | 73 | 72 | 70 | 68 | 102
103 | 88 | 87 | 85 | 84 | 82 | 81 | 79 | 78 | 76 | 75 | 73 | 71 | 70 | 103
104 | 89 | 88 | 86 | 85 | 83 | 82 | 81 | 79 | 78 | 76 | 74 | 73 | 71 | 104
| | | | | | | | | | | | | |
105 | 90 | 89 | 87 | 86 | 85 | 83 | 82 | 80 | 79 | 77 | 76 | 74 | 72 | 105
106 | 91 | 90 | 89 | 87 | 86 | 84 | 83 | 81 | 80 | 78 | 77 | 75 | 74 | 106
107 | 92 | 91 | 90 | 88 | 87 | 85 | 84 | 83 | 81 | 80 | 78 | 76 | 75 | 107
108 | 93 | 92 | 91 | 89 | 88 | 87 | 85 | 84 | 82 | 81 | 79 | 78 | 76 | 108
109 | 94 | 93 | 92 | 90 | 89 | 88 | 86 | 85 | 83 | 82 | 80 | 79 | 77 | 109
| | | | | | | | | | | | | |
110 | 96 | 94 | 93 | 92 | 90 | 89 | 87 | 86 | 85 | 83 | 82 | 80 | 79 | 110
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ |12°.0|13°.0|14°.0|15°.0|16°.0|17°.0|18°.0|19°.0|20°.0|21°.0|22°.0|23°.0|24°.0| _t._
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+=============================================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+(Dry
ther.)|24°.0|25°.0|26°.0|27°.0|28°.0|29°.0|30°.0|31°.0|32°.0|33°.0|34°.0|35°.0|36°.0|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
80 | 32 | 29 | 25 | 21 | 15 | 8 | -3 | -27 | | | | | | 80
81 | 35 | 31 | 28 | 24 | 18 | 12 | +3 | -11 | | | | | | 81
82 | 37 | 33 | 30 | 26 | 22 | 16 | 9 | -2 | -24 | | | | | 82
83 | 39 | 35 | 32 | 28 | 24 | 19 | 13 | +5 | -9 | | | | | 83
84 | 41 | 37 | 34 | 30 | 27 | 22 | 17 | 10 | 0 | -20 | | | | 84
| | | | | | | | | | | | | |
85 | 42 | 39 | 36 | 32 | 29 | 25 | 20 | 14 | +6 | -7 | -54 | | | 85
86 | 44 | 41 | 38 | 35 | 31 | 28 | 23 | 18 | 11 | +1 | -17 | | | 86
87 | 46 | 43 | 40 | 37 | 33 | 30 | 26 | 21 | 15 | 7 | -5 | -38 | | 87
88 | 48 | 45 | 42 | 39 | 35 | 32 | 28 | 24 | 19 | 12 | +3 | -13 | | 88
89 | 49 | 47 | 44 | 41 | 38 | 34 | 31 | 27 | 22 | 16 | 9 | -2 | -28 | 89
| | | | | | | | | | | | | |
90 | 51 | 48 | 46 | 43 | 40 | 36 | 32 | 29 | 25 | 20 | 13 | +4 | -10 | 90
91 | 53 | 50 | 47 | 45 | 42 | 38 | 35 | 32 | 28 | 23 | 18 | 10 | 0 | 91
92 | 54 | 52 | 49 | 46 | 44 | 41 | 37 | 34 | 30 | 26 | 21 | 15 | +7 | 92
93 | 56 | 53 | 51 | 48 | 46 | 43 | 39 | 36 | 32 | 29 | 24 | 19 | 12 | 93
94 | 57 | 55 | 53 | 50 | 47 | 45 | 42 | 38 | 35 | 31 | 27 | 22 | 16 | 94
| | | | | | | | | | | | | |
95 | 59 | 56 | 54 | 52 | 49 | 46 | 44 | 40 | 37 | 33 | 30 | 25 | 20 | 95
96 | 60 | 58 | 56 | 53 | 51 | 48 | 46 | 43 | 39 | 36 | 32 | 28 | 24 | 96
97 | 61 | 59 | 57 | 55 | 53 | 50 | 47 | 45 | 41 | 38 | 34 | 31 | 26 | 97
98 | 63 | 61 | 59 | 57 | 54 | 52 | 49 | 47 | 44 | 40 | 37 | 33 | 29 | 98
99 | 64 | 62 | 60 | 58 | 56 | 54 | 51 | 48 | 46 | 43 | 39 | 35 | 32 | 99
| | | | | | | | | | | | | |
100 | 66 | 64 | 62 | 60 | 57 | 55 | 53 | 50 | 48 | 45 | 41 | 38 | 34 | 100
101 | 67 | 65 | 63 | 61 | 59 | 57 | 54 | 52 | 49 | 47 | 44 | 40 | 37 | 101
102 | 68 | 66 | 65 | 63 | 61 | 58 | 56 | 54 | 51 | 49 | 46 | 43 | 39 | 102
103 | 70 | 68 | 66 | 64 | 62 | 60 | 58 | 55 | 53 | 50 | 48 | 45 | 41 | 103
104 | 71 | 69 | 67 | 65 | 63 | 61 | 59 | 57 | 55 | 52 | 50 | 47 | 44 | 104
| | | | | | | | | | | | | |
105 | 72 | 70 | 69 | 67 | 65 | 63 | 61 | 59 | 56 | 54 | 52 | 49 | 46 | 105
106 | 74 | 72 | 70 | 68 | 66 | 64 | 62 | 60 | 58 | 56 | 53 | 51 | 48 | 106
107 | 75 | 73 | 71 | 70 | 68 | 66 | 64 | 62 | 60 | 57 | 55 | 52 | 50 | 107
108 | 76 | 74 | 73 | 71 | 69 | 67 | 65 | 63 | 61 | 59 | 57 | 54 | 52 | 108
109 | 77 | 76 | 74 | 72 | 71 | 69 | 67 | 65 | 63 | 61 | 58 | 56 | 54 | 109
| | | | | | | | | | | | | |
110 | 79 | 77 | 75 | 74 | 72 | 70 | 68 | 66 | 64 | 62 | 60 | 58 | 55 | 110
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ |24°.0|25°.0|26°.0|27°.0|28°.0|29°.0|30°.0|31°.0|32°.0|33°.0|34°.0|35°.0|36°.0| _t._
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
TABLE I.——TEMPERATURE OF THE DEW-POINT, IN DEGREES FAHRENHEIT.
======+=============================================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+(Dry
ther.)|36°.0|37°.0|38°.0|39°.0|40°.0|41°.0|42°.0|43°.0|44°.0|45°.0|46°.0|47°.0|48°.0|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
89 | -28 | | | | | | | | | | | | | 89
| | | | | | | | | | | | | |
90 | -10 | | | | | | | | | | | | | 90
91 | 0 | -22 | | | | | | | | | | | | 91
92 | +7 | -7 | -16 | | | | | | | | | | | 92
93 | 12 | +2 | -4 | | | | | | | | | | | 93
94 | 16 | 8 | +4 | -37 | | | | | | | | | | 94
| | | | | | | | | | | | | |
95 | 20 | 13 | 10 | -12 | | | | | | | | | | 95
96 | 24 | 15 | 15 | -1 | -25 | | | | | | | | | 96
97 | 26 | 21 | 19 | +7 | -8 | | | | | | | | | 97
98 | 29 | 25 | 23 | 12 | +2 | -18 | | | | | | | | 98
99 | 32 | 28 | 26 | 17 | 9 | -4 | -42 | | | | | | | 99
| | | | | | | | | | | | | |
100 | 34 | 30 | 29 | 21 | 14 | +5 | -12 | | | | | | | 100
101 | 37 | 32 | 32 | 24 | 18 | 11 | 0 | -25 | | | | | | 101
102 | 39 | 35 | 34 | 27 | 22 | 16 | +7 | -7 | | | | | | 102
103 | 41 | 38 | 34 | 30 | 26 | 20 | 13 | +3 | -16 | | | | | 103
104 | 44 | 40 | 37 | 32 | 29 | 24 | 18 | 10 | -2 | -38 | | | | 104
| | | | | | | | | | | | | |
105 | 46 | 43 | 39 | 35 | 31 | 27 | 22 | 15 | +6 | -10 | | | | 105
106 | 48 | 45 | 42 | 38 | 34 | 30 | 25 | 20 | 12 | +1 | -22 | | | 106
107 | 50 | 47 | 44 | 40 | 37 | 32 | 28 | 24 | 17 | 9 | -5 | | | 107
108 | 52 | 49 | 46 | 43 | 39 | 35 | 31 | 27 | 21 | 14 | +5 | -13 | | 108
109 | 54 | 51 | 48 | 45 | 42 | 38 | 34 | 30 | 25 | 19 | 12 | 0 | -28 | 109
| | | | | | | | | | | | | |
110 | 55 | 53 | 50 | 47 | 44 | 41 | 37 | 33 | 28 | 23 | 17 | +8 | -7 | 110
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ |36°.0|37°.0|38°.0|39°.0|40°.0|41°.0|42°.0|43°.0|44°.0|45°.0|46°.0|47°.0|48°.0| _t._
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
TABLE II.——RELATIVE HUMIDITY, PER CENT.
======+================================================================+=======
_t_ | Difference between the dry and wet thermometers (_t_——_t′_). | _t_
(Dry +----+----+----+----+----+----+----+----+----+----+----+----+----+ (Dry
ther.)|0°.2|0°.4|0°.6|0°.8|1°.0|1°.2|1°.4|1°.6|1°.8|2°.0|2°.2|2°.4|2°.6| ther.)
------+----+----+----+----+----+----+----+----+----+----+----+----+----+-------
-40 | 46 | | | | | | | | | | | | | -40
-39 | 49 | | | | | | | | | | | | | -39
-38 | 51 | | | | | | | | | | | | | -38
-37 | 54 | | | | | | | | | | | | | -37
-36 | 56 | | | | | | | | | | | | | -36
| | | | | | | | | | | | | |
-35 | 59 | | | | | | | | | | | | | -35
-34 | 61 | 22 | | | | | | | | | | | | -34
-33 | 63 | 25 | | | | | | | | | | | | -33
-32 | 65 | 30 | | | | | | | | | | | | -32
-31 | 67 | 34 | | | | | | | | | | | | -31
| | | | | | | | | | | | | |
-30 | 69 | 38 | | | | | | | | | | | | -30
-29 | 71 | 42 | | | | | | | | | | | | -29
-28 | 72 | 45 | 17 | | | | | | | | | | | -28
-27 | 74 | 48 | 22 | | | | | | | | | | | -27
-26 | 76 | 51 | 26 | | | | | | | | | | | -26
| | | | | | | | | | | | | |
-25 | 77 | 53 | 31 | | | | | | | | | | | -25
-24 | 78 | 56 | 34 | 12 | | | | | | | | | | -24
-23 | 79 | 58 | 37 | 16 | | | | | | | | | | -23
-22 | 80 | 60 | 40 | 20 | | | | | | | | | | -22
-21 | 81 | 62 | 44 | 25 | | | | | | | | | | -21
| | | | | | | | | | | | | |
-20 | 82 | 64 | 47 | 29 | 11 | | | | | | | | | -20
-19 | 83 | 66 | 49 | 33 | 16 | | | | | | | | | -19
-18 | 84 | 68 | 52 | 36 | 20 | | | | | | | | | -18
-17 | 85 | 70 | 54 | 39 | 24 | 9 | | | | | | | | -17
-16 | 86 | 71 | 57 | 43 | 28 | 14 | | | | | | | | -16
| | | | | | | | | | | | | |
-15 | 86 | 73 | 59 | 46 | 32 | 19 | | | | | | | | -15
-14 | 87 | 74 | 61 | 48 | 36 | 23 | 10 | | | | | | | -14
-13 | 88 | 76 | 63 | 51 | 39 | 27 | 15 | | | | | | | -13
-12 | 88 | 77 | 65 | 53 | 42 | 30 | 19 | 7 | | | | | | -12
-11 | 89 | 78 | 67 | 56 | 45 | 34 | 23 | 12 | | | | | | -11
| | | | | | | | | | | | | |
-10 | 90 | 79 | 68 | 58 | 48 | 37 | 26 | 16 | 5 | | | | | -10
-9 | 90 | 80 | 70 | 60 | 50 | 40 | 30 | 20 | 10 | | | | | -9
-8 | 90 | 81 | 71 | 62 | 52 | 43 | 33 | 24 | 14 | 5 | | | | -8
-7 | 91 | 82 | 73 | 63 | 54 | 45 | 36 | 27 | 18 | 9 | | | | -7
-6 | 91 | 83 | 74 | 65 | 56 | 48 | 39 | 31 | 22 | 13 | 5 | | | -6
| | | | | | | | | | | | | |
-5 | 92 | 83 | 75 | 67 | 58 | 50 | 42 | 34 | 25 | 17 | 9 | | | -5
-4 | 92 | 84 | 76 | 68 | 60 | 52 | 45 | 37 | 29 | 21 | 13 | 5 | | -4
-3 | 92 | 85 | 77 | 70 | 62 | 55 | 47 | 40 | 32 | 25 | 17 | 10 | | -3
-2 | 93 | 86 | 78 | 71 | 64 | 57 | 50 | 42 | 35 | 28 | 21 | 14 | 7 | -2
-1 | 93 | 86 | 79 | 72 | 66 | 59 | 52 | 45 | 38 | 31 | 25 | 18 | 11 | -1
| | | | | | | | | | | | | |
0 | 93 | 87 | 80 | 74 | 67 | 61 | 54 | 48 | 41 | 35 | 28 | 22 | 15 | 0
+1 | 94 | 87 | 81 | 75 | 69 | 63 | 56 | 50 | 44 | 38 | 32 | 25 | 19 | +1
2 | 94 | 88 | 82 | 76 | 70 | 64 | 58 | 52 | 46 | 40 | 35 | 29 | 23 | 2
3 | 94 | 88 | 83 | 77 | 71 | 66 | 60 | 54 | 49 | 43 | 37 | 32 | 26 | 3
4 | 94 | 89 | 83 | 78 | 73 | 67 | 62 | 56 | 51 | 45 | 40 | 34 | 29 | 4
| | | | | | | | | | | | | |
5 | 95 | 89 | 84 | 79 | 74 | 68 | 63 | 58 | 53 | 48 | 42 | 37 | 32 | 5
6 | 95 | 90 | 85 | 80 | 75 | 70 | 65 | 60 | 54 | 50 | 44 | 39 | 34 | 6
7 | 95 | 90 | 85 | 80 | 76 | 71 | 66 | 61 | 56 | 51 | 47 | 42 | 37 | 7
8 | 95 | 91 | 86 | 81 | 76 | 72 | 67 | 62 | 58 | 53 | 49 | 44 | 39 | 8
9 | 96 | 91 | 86 | 82 | 77 | 73 | 68 | 64 | 59 | 55 | 51 | 46 | 42 | 9
| | | | | | | | | | | | | |
10 | 96 | 91 | 87 | 83 | 78 | 74 | 69 | 65 | 61 | 57 | 52 | 48 | 44 | 10
11 | 96 | 92 | 87 | 83 | 79 | 75 | 71 | 66 | 62 | 58 | 54 | 50 | 46 | 11
12 | 96 | 92 | 88 | 84 | 80 | 76 | 72 | 68 | 64 | 60 | 56 | 52 | 48 | 12
13 | 96 | 92 | 88 | 84 | 81 | 77 | 73 | 69 | 65 | 61 | 58 | 54 | 50 | 13
14 | 96 | 93 | 89 | 85 | 81 | 78 | 74 | 70 | 67 | 63 | 59 | 56 | 52 | 14
| | | | | | | | | | | | | |
15 | 96 | 93 | 89 | 86 | 82 | 79 | 75 | 71 | 68 | 64 | 61 | 57 | 54 | 15
16 | 97 | 93 | 90 | 86 | 83 | 79 | 76 | 73 | 69 | 66 | 62 | 59 | 56 | 16
17 | 97 | 93 | 90 | 87 | 83 | 80 | 77 | 74 | 70 | 67 | 64 | 60 | 57 | 17
18 | 97 | 94 | 90 | 87 | 84 | 81 | 78 | 74 | 71 | 68 | 65 | 62 | 59 | 18
19 | 97 | 94 | 91 | 88 | 84 | 81 | 78 | 75 | 72 | 69 | 66 | 63 | 60 | 19
| | | | | | | | | | | | | |
20 | 97 | 94 | 91 | 88 | 85 | 82 | 79 | 76 | 73 | 70 | 67 | 64 | 61 | 20
------+----+----+----+----+----+----+----+----+----+----+----+----+----+-------
_t._ |0°.2|0°.4|0°.6|0°.8|1°.0|1°.2|1°.4|1°.6|1°.8|2°.0|2°.2|2°.4|2°.6| _t._
======+====+====+====+====+====+====+====+====+====+====+====+====+====+=======
TABLE II.——RELATIVE HUMIDITY, PER CENT.
======+===========================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_).| _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+(Dry
ther.)| 2°.6| 2°.8| 3°.0| 3°.2| 3°.4| 3°.6| 3°.8| 4°.0| 4°.2| 4°.4|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
-2 | 7 | | | | | | | | | | -2
-1 | 11 | 4 | | | | | | | | | -1
| | | | | | | | | | |
0 | 15 | 9 | | | | | | | | | 0
+1 | 19 | 13 | 7 | | | | | | | | +1
2 | 23 | 17 | 11 | 5 | | | | | | | 2
3 | 26 | 20 | 15 | 9 | 4 | | | | | | 3
4 | 29 | 24 | 18 | 13 | 8 | 2 | | | | | 4
| | | | | | | | | | |
5 | 32 | 27 | 22 | 16 | 11 | 6 | | | | | 5
6 | 34 | 29 | 25 | 20 | 15 | 10 | 5 | | | | 6
7 | 37 | 32 | 28 | 23 | 18 | 13 | 9 | 4 | | | 7
8 | 39 | 35 | 30 | 26 | 21 | 17 | 12 | 8 | 3 | | 8
9 | 42 | 37 | 33 | 28 | 24 | 20 | 15 | 11 | 7 | 2 | 9
| | | | | | | | | | |
10 | 44 | 40 | 35 | 31 | 27 | 23 | 19 | 14 | 10 | 6 | 10
11 | 46 | 42 | 38 | 34 | 30 | 26 | 22 | 18 | 14 | 10 | 11
12 | 48 | 44 | 40 | 36 | 32 | 28 | 25 | 21 | 17 | 13 | 12
13 | 50 | 46 | 42 | 39 | 35 | 31 | 27 | 24 | 20 | 16 | 13
14 | 52 | 48 | 45 | 41 | 37 | 34 | 30 | 27 | 23 | 19 | 14
| | | | | | | | | | |
15 | 54 | 50 | 47 | 43 | 40 | 36 | 33 | 29 | 26 | 23 | 15
16 | 56 | 52 | 49 | 46 | 42 | 39 | 36 | 32 | 29 | 25 | 16
17 | 57 | 54 | 51 | 48 | 44 | 41 | 38 | 35 | 31 | 28 | 17
18 | 59 | 56 | 53 | 49 | 46 | 43 | 40 | 37 | 34 | 31 | 18
19 | 60 | 57 | 54 | 51 | 48 | 45 | 42 | 39 | 36 | 33 | 19
| | | | | | | | | | |
20 | 61 | 58 | 56 | 53 | 50 | 47 | 44 | 41 | 38 | 35 | 20
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ | 2°.6| 2°.8| 3°.0| 3°.2| 3°.4| 3°.6| 3°.8| 4°.0| 4°.2| 4°.4| _t._
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
_t._ | 4°.6| 4°.8| 5°.0| 5°.2| 5°.4| 5°.6| 5°.8| 6°.0| 6°.2| 6°.4| _t._
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
8 | | | | | | | | | | | 8
9 | | | | | | | | | | | 9
| | | | | | | | | | |
10 | 2 | | | | | | | | | | 10
11 | 6 | 2 | | | | | | | | | 11
12 | 9 | 5 | 2 | | | | | | | | 12
13 | 13 | 9 | 5 | 2 | | | | | | | 13
14 | 16 | 12 | 9 | 5 | 2 | | | | | | 14
| | | | | | | | | | |
15 | 19 | 16 | 12 | 9 | 5 | 2 | | | | | 15
16 | 22 | 19 | 16 | 12 | 9 | 6 | 2 | | | | 16
17 | 25 | 22 | 19 | 16 | 12 | 9 | 6 | 3 | | | 17
18 | 28 | 25 | 22 | 19 | 16 | 13 | 9 | 6 | 3 | | 18
19 | 30 | 27 | 24 | 21 | 19 | 16 | 13 | 10 | 7 | 4 | 19
| | | | | | | | | | |
20 | 33 | 30 | 27 | 24 | 21 | 19 | 16 | 13 | 10 | 7 | 20
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ | 4°.6| 4°.8| 5°.0| 5°.2| 5°.4| 5°.6| 5°.8| 6°.0| 6°.2| 6°.4| _t._
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
TABLE II.——RELATIVE HUMIDITY, PER CENT.
======+=======================================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+(Dry
ther.)| 0°.5| 1°.0| 1°.5| 2°.0| 2°.5| 3°.0| 3°.5| 4°.0| 4°.5| 5°.0| 5°.5| 6°.0|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
20 | 92 | 85 | 77 | 70 | 63 | 56 | 48 | 41 | 34 | 27 | 20 | 13 | 20
21 | 93 | 85 | 78 | 71 | 64 | 57 | 50 | 43 | 36 | 29 | 23 | 16 | 21
22 | 93 | 86 | 79 | 72 | 65 | 58 | 51 | 45 | 38 | 32 | 25 | 19 | 22
23 | 93 | 86 | 80 | 73 | 66 | 60 | 53 | 46 | 40 | 34 | 27 | 21 | 23
24 | 93 | 87 | 80 | 74 | 67 | 61 | 54 | 48 | 42 | 36 | 30 | 24 | 24
| | | | | | | | | | | | |
25 | 94 | 87 | 81 | 74 | 68 | 62 | 56 | 50 | 44 | 38 | 32 | 26 | 25
26 | 94 | 88 | 81 | 75 | 69 | 63 | 57 | 51 | 45 | 40 | 34 | 28 | 26
27 | 94 | 88 | 82 | 76 | 70 | 64 | 59 | 53 | 47 | 42 | 36 | 30 | 27
28 | 94 | 88 | 82 | 77 | 71 | 65 | 60 | 54 | 49 | 43 | 38 | 33 | 28
29 | 94 | 89 | 83 | 77 | 72 | 66 | 61 | 56 | 50 | 45 | 40 | 35 | 29
| | | | | | | | | | | | |
30 | 94 | 89 | 84 | 78 | 73 | 67 | 62 | 57 | 52 | 47 | 41 | 36 | 30
31 | 95 | 89 | 84 | 79 | 74 | 68 | 63 | 58 | 53 | 48 | 43 | 38 | 31
32 | 95 | 90 | 84 | 79 | 74 | 69 | 64 | 59 | 54 | 50 | 45 | 40 | 32
33 | 95 | 90 | 85 | 80 | 75 | 70 | 65 | 60 | 56 | 51 | 47 | 42 | 33
34 | 95 | 91 | 86 | 81 | 75 | 72 | 67 | 62 | 57 | 53 | 48 | 44 | 34
| | | | | | | | | | | | |
35 | 95 | 91 | 86 | 82 | 76 | 73 | 69 | 65 | 59 | 54 | 50 | 45 | 35
36 | 96 | 91 | 86 | 82 | 77 | 73 | 70 | 66 | 61 | 56 | 51 | 47 | 36
37 | 96 | 91 | 87 | 82 | 78 | 74 | 70 | 66 | 62 | 57 | 52 | 48 | 37
38 | 96 | 92 | 87 | 83 | 79 | 75 | 71 | 67 | 63 | 58 | 54 | 50 | 38
39 | 96 | 92 | 88 | 83 | 79 | 75 | 72 | 68 | 63 | 59 | 55 | 52 | 39
| | | | | | | | | | | | |
40 | 96 | 92 | 88 | 84 | 80 | 76 | 72 | 68 | 64 | 60 | 56 | 53 | 40
41 | 96 | 92 | 88 | 84 | 80 | 76 | 72 | 69 | 65 | 61 | 57 | 54 | 41
42 | 96 | 92 | 88 | 84 | 81 | 77 | 73 | 69 | 65 | 62 | 58 | 55 | 42
43 | 96 | 92 | 88 | 85 | 81 | 77 | 74 | 70 | 66 | 63 | 59 | 56 | 43
44 | 96 | 92 | 88 | 85 | 81 | 78 | 74 | 70 | 67 | 63 | 60 | 57 | 44
| | | | | | | | | | | | |
45 | 96 | 92 | 89 | 85 | 82 | 78 | 75 | 71 | 67 | 64 | 61 | 58 | 45
46 | 96 | 93 | 89 | 85 | 82 | 79 | 75 | 72 | 68 | 65 | 61 | 58 | 46
47 | 96 | 93 | 89 | 86 | 83 | 79 | 76 | 72 | 69 | 66 | 62 | 59 | 47
48 | 96 | 93 | 89 | 86 | 83 | 79 | 76 | 73 | 69 | 66 | 63 | 60 | 48
49 | 97 | 93 | 90 | 86 | 83 | 80 | 76 | 73 | 70 | 67 | 63 | 60 | 49
| | | | | | | | | | | | |
50 | 97 | 93 | 90 | 87 | 83 | 80 | 77 | 74 | 70 | 67 | 64 | 61 | 50
51 | 97 | 93 | 90 | 87 | 84 | 81 | 77 | 74 | 71 | 68 | 65 | 62 | 51
52 | 97 | 94 | 90 | 87 | 84 | 81 | 78 | 75 | 72 | 69 | 66 | 63 | 52
53 | 97 | 94 | 91 | 87 | 84 | 81 | 78 | 75 | 72 | 69 | 66 | 63 | 53
54 | 97 | 94 | 91 | 88 | 85 | 82 | 79 | 76 | 73 | 70 | 67 | 64 | 54
| | | | | | | | | | | | |
55 | 97 | 94 | 91 | 88 | 85 | 82 | 79 | 76 | 73 | 70 | 68 | 65 | 55
56 | 97 | 94 | 91 | 88 | 85 | 82 | 80 | 77 | 74 | 71 | 68 | 65 | 56
57 | 97 | 94 | 91 | 88 | 86 | 83 | 80 | 77 | 74 | 71 | 69 | 66 | 57
58 | 97 | 94 | 91 | 89 | 86 | 83 | 80 | 78 | 75 | 72 | 69 | 67 | 58
59 | 97 | 94 | 92 | 89 | 86 | 83 | 81 | 78 | 75 | 72 | 70 | 67 | 59
| | | | | | | | | | | | |
60 | 97 | 94 | 92 | 89 | 86 | 84 | 81 | 78 | 75 | 73 | 70 | 68 | 60
61 | 97 | 94 | 92 | 89 | 87 | 84 | 81 | 78 | 76 | 73 | 71 | 68 | 61
62 | 97 | 95 | 92 | 89 | 87 | 84 | 81 | 79 | 76 | 74 | 71 | 69 | 62
63 | 97 | 95 | 92 | 89 | 87 | 84 | 82 | 79 | 77 | 74 | 72 | 69 | 63
64 | 97 | 95 | 92 | 90 | 87 | 85 | 82 | 79 | 77 | 74 | 72 | 70 | 64
| | | | | | | | | | | | |
65 | 97 | 95 | 92 | 90 | 87 | 85 | 82 | 80 | 77 | 75 | 72 | 70 | 65
66 | 97 | 95 | 92 | 90 | 87 | 85 | 82 | 80 | 78 | 75 | 73 | 71 | 66
67 | 98 | 95 | 93 | 90 | 88 | 85 | 83 | 80 | 78 | 76 | 73 | 71 | 67
68 | 98 | 95 | 93 | 90 | 88 | 85 | 83 | 81 | 78 | 76 | 74 | 71 | 68
69 | 98 | 95 | 93 | 90 | 88 | 86 | 83 | 81 | 78 | 76 | 74 | 72 | 69
| | | | | | | | | | | | |
70 | 98 | 95 | 93 | 90 | 88 | 86 | 83 | 81 | 79 | 77 | 74 | 72 | 70
71 | 98 | 95 | 93 | 91 | 88 | 86 | 84 | 81 | 79 | 77 | 75 | 72 | 71
72 | 98 | 95 | 93 | 91 | 88 | 86 | 84 | 82 | 79 | 77 | 75 | 73 | 72
73 | 98 | 95 | 93 | 91 | 88 | 86 | 84 | 82 | 80 | 78 | 75 | 73 | 73
74 | 98 | 95 | 93 | 91 | 88 | 86 | 84 | 82 | 80 | 78 | 76 | 74 | 74
| | | | | | | | | | | | |
75 | 98 | 95 | 93 | 91 | 89 | 87 | 84 | 82 | 80 | 78 | 76 | 74 | 75
76 | 98 | 95 | 93 | 91 | 89 | 87 | 85 | 82 | 80 | 78 | 76 | 74 | 76
77 | 98 | 95 | 93 | 91 | 89 | 87 | 85 | 83 | 80 | 78 | 76 | 74 | 77
78 | 98 | 96 | 93 | 91 | 89 | 87 | 85 | 83 | 81 | 79 | 77 | 75 | 78
79 | 98 | 96 | 94 | 91 | 89 | 87 | 85 | 83 | 81 | 79 | 77 | 75 | 79
| | | | | | | | | | | | |
80 | 98 | 96 | 94 | 92 | 89 | 87 | 85 | 83 | 81 | 79 | 77 | 75 | 80
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ | 0°.5| 1°.0| 1°.5| 2°.0| 2°.5| 3°.0| 3°.5| 4°.0| 4°.5| 5°.0| 5°.5| 6°.0| _t._
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
TABLE II.——RELATIVE HUMIDITY, PER CENT.
======+=====================================================================+=====
_t_ | Difference between the dry and wet thermometers (_t-t′_). |_t_
(Dry +----+----+----+----+----+----+----+----+-----+-----+-----+-----+-----+(Dry
ther.)|6°.0|6°.5|7°.0|7°.5|8°.0|8°.5|9°.0|9°.5|10°.0|10°.5|11°.0|11°.5|12°.0|ther.)
------+----+----+----+----+----+----+----+----+-----+-----+-----+-----+-----+------
19 | 10 | | | | | | | | | | | | | 19
| | | | | | | | | | | | | |
20 | 13 | 6 | | | | | | | | | | | | 20
21 | 16 | 9 | 2 | | | | | | | | | | | 21
22 | 19 | 12 | 6 | | | | | | | | | | | 22
23 | 21 | 15 | 9 | 2 | | | | | | | | | | 23
24 | 24 | 17 | 11 | 6 | | | | | | | | | | 24
| | | | | | | | | | | | | |
25 | 26 | 20 | 14 | 8 | 3 | | | | | | | | | 25
26 | 28 | 23 | 17 | 11 | 6 | | | | | | | | | 26
27 | 30 | 25 | 19 | 14 | 9 | 3 | | | | | | | | 27
28 | 33 | 27 | 22 | 17 | 11 | 6 | 1 | | | | | | | 28
29 | 35 | 29 | 24 | 19 | 14 | 9 | 4 | | | | | | | 29
| | | | | | | | | | | | | |
30 | 36 | 31 | 26 | 22 | 17 | 12 | 7 | 2 | | | | | | 30
31 | 38 | 33 | 29 | 24 | 19 | 14 | 10 | 5 | | | | | | 31
32 | 40 | 35 | 31 | 26 | 21 | 17 | 12 | 8 | 3 | | | | | 32
33 | 42 | 37 | 33 | 28 | 24 | 19 | 15 | 10 | 6 | 2 | | | | 33
34 | 44 | 39 | 35 | 30 | 26 | 21 | 17 | 13 | 9 | 4 | | | | 34
| | | | | | | | | | | | | |
35 | 45 | 41 | 37 | 32 | 28 | 24 | 19 | 15 | 12 | 7 | 3 | | | 35
36 | 47 | 43 | 38 | 34 | 30 | 26 | 22 | 18 | 14 | 10 | 6 | 2 | | 36
37 | 48 | 44 | 40 | 36 | 32 | 28 | 24 | 20 | 16 | 12 | 8 | 5 | 1 | 37
38 | 50 | 46 | 42 | 38 | 34 | 30 | 26 | 22 | 18 | 15 | 11 | 7 | 3 | 38
39 | 52 | 48 | 44 | 40 | 36 | 32 | 28 | 24 | 20 | 17 | 13 | 9 | 6 | 39
| | | | | | | | | | | | | |
40 | 53 | 49 | 45 | 41 | 38 | 34 | 30 | 26 | 22 | 19 | 16 | 12 | 8 | 40
41 | 54 | 50 | 46 | 43 | 39 | 36 | 32 | 29 | 24 | 21 | 18 | 14 | 10 | 41
42 | 55 | 51 | 48 | 44 | 40 | 37 | 34 | 30 | 27 | 23 | 20 | 16 | 13 | 42
43 | 56 | 52 | 49 | 46 | 42 | 38 | 35 | 32 | 29 | 25 | 22 | 19 | 15 | 43
44 | 57 | 53 | 50 | 47 | 43 | 40 | 37 | 33 | 30 | 27 | 24 | 21 | 17 | 44
| | | | | | | | | | | | | |
45 | 58 | 54 | 51 | 48 | 44 | 41 | 38 | 35 | 32 | 29 | 25 | 22 | 19 | 45
46 | 58 | 55 | 52 | 49 | 46 | 42 | 39 | 36 | 33 | 30 | 27 | 23 | 21 | 46
47 | 59 | 56 | 53 | 50 | 47 | 44 | 40 | 38 | 34 | 31 | 28 | 25 | 22 | 47
48 | 60 | 56 | 53 | 51 | 48 | 45 | 42 | 39 | 36 | 33 | 30 | 27 | 24 | 48
49 | 60 | 57 | 54 | 52 | 49 | 46 | 43 | 40 | 37 | 34 | 31 | 29 | 26 | 49
| | | | | | | | | | | | | |
50 | 61 | 58 | 55 | 52 | 50 | 47 | 44 | 41 | 38 | 36 | 33 | 30 | 27 | 50
51 | 62 | 59 | 56 | 53 | 50 | 48 | 45 | 42 | 39 | 37 | 34 | 31 | 28 | 51
52 | 63 | 60 | 57 | 54 | 51 | 48 | 46 | 43 | 40 | 38 | 35 | 33 | 30 | 52
53 | 63 | 61 | 58 | 55 | 52 | 49 | 47 | 44 | 42 | 39 | 36 | 34 | 31 | 53
54 | 64 | 61 | 59 | 56 | 53 | 50 | 48 | 45 | 43 | 40 | 38 | 35 | 32 | 54
| | | | | | | | | | | | | |
55 | 65 | 62 | 59 | 57 | 54 | 51 | 49 | 46 | 43 | 41 | 39 | 36 | 34 | 55
56 | 65 | 63 | 60 | 57 | 55 | 52 | 50 | 47 | 44 | 42 | 40 | 37 | 35 | 56
57 | 66 | 64 | 61 | 58 | 55 | 53 | 50 | 48 | 45 | 43 | 40 | 38 | 36 | 57
58 | 67 | 64 | 61 | 59 | 56 | 53 | 51 | 49 | 46 | 44 | 42 | 39 | 37 | 58
59 | 67 | 65 | 62 | 60 | 57 | 54 | 52 | 49 | 47 | 45 | 43 | 40 | 38 | 59
| | | | | | | | | | | | | |
60 | 68 | 65 | 63 | 60 | 58 | 55 | 53 | 50 | 48 | 46 | 44 | 41 | 39 | 60
61 | 68 | 66 | 63 | 61 | 58 | 56 | 54 | 51 | 49 | 47 | 44 | 42 | 40 | 61
62 | 69 | 66 | 64 | 61 | 59 | 57 | 54 | 52 | 50 | 47 | 45 | 43 | 41 | 62
63 | 69 | 67 | 64 | 62 | 60 | 57 | 55 | 53 | 51 | 48 | 46 | 44 | 42 | 63
64 | 70 | 67 | 65 | 62 | 60 | 58 | 56 | 53 | 51 | 49 | 47 | 45 | 43 | 64
| | | | | | | | | | | | | |
65 | 70 | 68 | 65 | 63 | 61 | 59 | 56 | 54 | 52 | 50 | 48 | 46 | 44 | 65
66 | 71 | 68 | 66 | 63 | 61 | 59 | 57 | 55 | 53 | 51 | 49 | 47 | 45 | 66
67 | 71 | 69 | 66 | 64 | 62 | 60 | 58 | 55 | 53 | 51 | 49 | 47 | 45 | 67
68 | 71 | 69 | 67 | 65 | 63 | 60 | 58 | 56 | 54 | 52 | 50 | 48 | 46 | 68
69 | 72 | 70 | 67 | 65 | 63 | 61 | 59 | 57 | 55 | 53 | 51 | 49 | 47 | 69
| | | | | | | | | | | | | |
70 | 72 | 70 | 68 | 66 | 64 | 62 | 60 | 57 | 55 | 53 | 52 | 50 | 48 | 70
71 | 72 | 70 | 68 | 66 | 64 | 62 | 60 | 58 | 56 | 54 | 52 | 50 | 48 | 71
72 | 73 | 71 | 69 | 67 | 65 | 63 | 61 | 59 | 57 | 55 | 53 | 51 | 49 | 72
73 | 73 | 71 | 69 | 67 | 65 | 63 | 61 | 59 | 57 | 55 | 53 | 52 | 50 | 73
74 | 74 | 72 | 70 | 68 | 66 | 64 | 62 | 60 | 58 | 56 | 54 | 52 | 50 | 74
| | | | | | | | | | | | | |
75 | 74 | 72 | 70 | 68 | 66 | 64 | 62 | 60 | 58 | 56 | 55 | 53 | 51 | 75
76 | 74 | 72 | 70 | 68 | 66 | 64 | 63 | 61 | 59 | 57 | 55 | 53 | 52 | 76
77 | 74 | 73 | 71 | 69 | 67 | 65 | 63 | 61 | 59 | 57 | 56 | 54 | 52 | 77
78 | 75 | 73 | 71 | 69 | 67 | 65 | 63 | 62 | 60 | 58 | 56 | 54 | 53 | 78
79 | 75 | 73 | 71 | 70 | 68 | 66 | 64 | 62 | 60 | 58 | 57 | 55 | 53 | 79
| | | | | | | | | | | | | |
80 | 75 | 73 | 72 | 70 | 68 | 66 | 64 | 63 | 61 | 59 | 57 | 55 | 54 | 80
------+----+----+----+----+----+----+----+----+-----+-----+-----+-----+-----+------
_t._ |6°.0|6°.5|7°.0|7°.5|8°.0|8°.5|9°.0|9°.5|10°.0|10°.5|11°.0|11°.5|12°0|_t._
======+====+====+====+====+====+====+====+====+=====+=====+=====+=====+=====+======
TABLE II.——RELATIVE HUMIDITY, PER CENT.
======+=============================================================================+======
_t_ | Difference between the dry and wet thermometers (_t-t′_). | _t_
(Dry +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+(Dry
ther.)|12°.0|12°.5|13°.0|13°.5|14°.0|14°.5|15°.0|15°.5|16°.0|16°.5|17°.0|17°.5|18°.0|ther.)
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
40 | 8 | 5 | 1 | | | | | | | | | | | 40
41 | 10 | 7 | 4 | | | | | | | | | | | 41
42 | 13 | 10 | 6 | 3 | | | | | | | | | | 42
43 | 15 | 12 | 9 | 5 | 2 | | | | | | | | | 43
44 | 17 | 14 | 11 | 8 | 5 | 1 | | | | | | | | 44
| | | | | | | | | | | | | |
45 | 19 | 16 | 13 | 10 | 7 | 4 | 1 | | | | | | | 45
46 | 21 | 18 | 15 | 12 | 9 | 6 | 3 | | | | | | | 46
47 | 22 | 20 | 16 | 14 | 11 | 8 | 5 | 3 | | | | | | 47
48 | 24 | 21 | 19 | 16 | 13 | 10 | 7 | 5 | 2 | | | | | 48
49 | 26 | 23 | 20 | 17 | 15 | 12 | 9 | 7 | 4 | 1 | | | | 49
| | | | | | | | | | | | | |
50 | 27 | 24 | 22 | 19 | 16 | 14 | 11 | 9 | 6 | 4 | 1 | | | 50
51 | 28 | 26 | 23 | 21 | 18 | 16 | 13 | 10 | 8 | 5 | 3 | | | 51
52 | 30 | 27 | 24 | 22 | 20 | 17 | 15 | 12 | 10 | 7 | 5 | | | 52
53 | 31 | 29 | 26 | 24 | 21 | 19 | 16 | 14 | 12 | 9 | 7 | 4 | 2 | 53
54 | 32 | 30 | 28 | 25 | 23 | 20 | 18 | 15 | 13 | 11 | 8 | 6 | 4 | 54
| | | | | | | | | | | | | |
55 | 34 | 31 | 29 | 26 | 24 | 22 | 19 | 17 | 15 | 12 | 10 | 8 | 6 | 55
56 | 35 | 33 | 30 | 28 | 25 | 23 | 21 | 19 | 16 | 14 | 12 | 10 | 8 | 56
57 | 36 | 34 | 32 | 29 | 27 | 24 | 22 | 20 | 18 | 16 | 13 | 11 | 9 | 57
58 | 37 | 35 | 33 | 30 | 28 | 26 | 24 | 21 | 19 | 17 | 15 | 13 | 11 | 58
59 | 38 | 36 | 34 | 31 | 29 | 27 | 25 | 23 | 21 | 18 | 16 | 14 | 12 | 59
| | | | | | | | | | | | | |
60 | 39 | 37 | 34 | 32 | 30 | 28 | 26 | 24 | 22 | 20 | 18 | 16 | 14 | 60
61 | 40 | 38 | 35 | 33 | 32 | 29 | 27 | 25 | 23 | 21 | 19 | 17 | 15 | 61
62 | 41 | 39 | 37 | 34 | 32 | 30 | 28 | 26 | 24 | 22 | 20 | 18 | 16 | 62
63 | 42 | 40 | 38 | 35 | 33 | 31 | 29 | 28 | 26 | 24 | 22 | 20 | 18 | 63
64 | 43 | 41 | 38 | 36 | 34 | 32 | 30 | 29 | 27 | 25 | 23 | 21 | 19 | 64
| | | | | | | | | | | | | |
65 | 44 | 42 | 39 | 37 | 35 | 33 | 31 | 29 | 28 | 26 | 24 | 22 | 20 | 65
66 | 45 | 42 | 40 | 38 | 36 | 34 | 32 | 30 | 29 | 27 | 25 | 23 | 22 | 66
67 | 45 | 43 | 41 | 39 | 37 | 35 | 33 | 32 | 30 | 28 | 26 | 25 | 23 | 67
68 | 46 | 44 | 42 | 40 | 38 | 36 | 34 | 33 | 31 | 29 | 27 | 26 | 24 | 68
69 | 47 | 45 | 43 | 41 | 39 | 37 | 35 | 33 | 32 | 30 | 28 | 26 | 25 | 69
| | | | | | | | | | | | | |
70 | 48 | 46 | 44 | 42 | 40 | 38 | 36 | 34 | 33 | 31 | 29 | 27 | 26 | 70
71 | 48 | 46 | 45 | 43 | 41 | 39 | 37 | 35 | 34 | 32 | 30 | 28 | 27 | 71
72 | 49 | 47 | 45 | 43 | 42 | 40 | 38 | 36 | 35 | 33 | 31 | 30 | 28 | 72
73 | 50 | 48 | 46 | 44 | 42 | 41 | 39 | 37 | 35 | 34 | 32 | 30 | 29 | 73
74 | 50 | 48 | 47 | 45 | 43 | 41 | 40 | 38 | 36 | 35 | 33 | 31 | 30 | 74
| | | | | | | | | | | | | |
75 | 51 | 49 | 47 | 46 | 44 | 42 | 40 | 39 | 37 | 35 | 34 | 32 | 31 | 75
76 | 52 | 50 | 48 | 46 | 45 | 43 | 41 | 39 | 38 | 36 | 35 | 33 | 31 | 76
77 | 52 | 50 | 49 | 47 | 45 | 44 | 42 | 40 | 39 | 37 | 35 | 34 | 32 | 77
78 | 53 | 51 | 49 | 48 | 46 | 44 | 43 | 41 | 39 | 38 | 36 | 35 | 33 | 78
79 | 53 | 52 | 50 | 48 | 47 | 45 | 43 | 42 | 40 | 39 | 37 | 36 | 34 | 79
| | | | | | | | | | | | | |
80 | 54 | 52 | 51 | 49 | 47 | 45 | 44 | 42 | 41 | 39 | 38 | 36 | 35 | 80
------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+------
_t._ |12°.0|12°.5|13°.0|13°.5|14°.0|14°.5|15°.0|15°.5|16°.0|16°.5|17°.0|17°.5|18°.0| _t._
======+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+=====+======
TABLE II.——RELATIVE HUMIDITY, PER CENT.