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^ ,, INSTRUCTIONS.

:\ FOK

COOPERATIVE OBSERVERS.

CIRCULARS B AND C, INSTRUMENT DIVISION.

FIFTH EDITION.

WASHINGTON:
GOVERNMENT PEINTINQ OFIIOB.

1915.

ii I

^B.N.«. »R30^ !.„... „„,.,...

U. S. DEPARTMENT OF AGRICULTURE,
,'.; WEATHER BUREAU. )U5

-^ CHARLES F. MARVIN, Chief.

I
1

TABLE OF CONTENTS.

Page.

Introduction 5

I. Instructions for the erection and care of instruments 6

The object of temperature readings and exposure of thermometers 6

General description of thermometers 8

Instructions for reuniting detached columns of alcohol 10

Instructions for mounting maximum and minimum thermometers 14

The rain gage 17

How to measure rainfall and snowfall 19

General instructions about instruments 21

II. Making and recording observations 22

Temperature records 23

Precipitation records 24

Miscellaneous phenomena 25

Nomenclature 27

Form 1009, meteorological, sample monthly record 29

III. Earthquakes and instructions for their non-instrumental observation 31

Importance of earthquake data 31

Why the Weather Bureau should collect earthquake data 31

Request for cooperative observers 31

Instructions for the collection of earthquake data 32

LIST OF ILLUSTRATIONS.

Circular B & C, Instrument Division.

(Fifth edition.)

Page.

Thermometer shelter and rain gage for cooperative observers Frontispiece.

Fig. 1. Maximum and minimum thermometers on board support 9

Fig. 2. Showing first process of reuniting alcohol column in mimimum ther-
mometer i 11

Fig. 3. Showing second process of reuniting alcohol column in minimum ther-
mometer 12

Fig. 4. Showing third process for reuniting alcohol column in minimum ther-
mometer 13

Fig. 5. Setting maximum thermometer, board support 14

Fig. 6. Setting minimum thermometer, board support 14

Fig. 7. Thermometer supports, Townsend pattern 15

Fig. 8. Setting maximum thermometer, Townsend support 16

Fig. 9. Rain gags, showing details of 18

Fig. 10. Rain gage, and box support 19

INSTRUCTIONS FOR COOPERATIVE OBSERVERS OF THE

WEATHER BUREAU.

INTRODUCTION.

The object of this pamphlet is to furnish cooperative observers
with brief instructions for their guidance in taking and recording
meteorological observations, more especially of temperature and
rainfall, and for reporting earthquakes.

To render these observations of the greatest value and to facilitate
their use in investigating questions relating to chmate, it is important
that a uniform system for the exposure of the instruments and the
recording of the observations be adopted.

There are at this writing about 4,500 cooperative observers in the
United States. The records furnished by these observers are of great
value in affording information upon which many of the important
pubUcations of the Weather Bureau are based, and it is the poUcy of
the bureau to foster and encourage the keeping of such records. The
Annual Report of the Chief of the Weather Bureau, and the Monthly
and Annual Summaries of the several sections of the Climatological
Service of the bureau contain more or less complete summaries of
the observations, and through their wide dissemination the public is
furnished extensive and reUable data concerning the pecuUarities of
climate in every section of the country. Besides the records men-
tioned above the • observers furnish reports that form in part the
basis of the National Weather and Crop Bulletin, which gives from
week to week during the principal growing season, in the most
prompt manner, information as to the weather and crop conditions.
The cooperative observer who each day faithfully records the read-
ings of his instruments and notes the meteorological conditions pre-
vailing at lus station is performing a valuable public service. The
publications in which his records appear are constantly consulted by
persons in practically every walk of life, seeking information regard-
ing climatic conditions from the most authoritative sources.

Cooperative observers receive no money compensation for their
services, but they regularly receive such of the pubUcations of the
Weather Bureau as can be furnished free of cost.

As the value of a meteorological record increases with the length
of the period covered, continuity of record is of the utmost impor-
tance, and it is urgently recommended that those who undertake to
conduct observations endeavor to provide, as far as practicable, for

6 IKSTRUCTIONS FOR COOPERATIVE OBSERVERS.

an uninterrupted series. A member of the observer's family, or other
competent person, should be fully instructed in the matter of taking
and recording observations, so that no break in the record will result
from the temporary absence of the observer or from his inability
from any cause to make the necessary observations.

For the purpose of securing the observations necessary to meet the
requirements of those entitled to such information, the Chief of the
Weather Bureau is authorized by law to loan instruments to persons
willing to take thef observations, on certain conditions. These con-
ditions, in the main, are the safe-keeping of the instruments, their
return to the Weather Bureau if for any reason the station is discon-
tinued, and the furnishing of copies of the observations to the section
director of the cUmatological service of the Weather Bureau for the
State where located, free of expense to the Government.

Cooperative observers are usually furnished with maximum and
minimum thermometers, instrument shelters, and rain gages, but not
with barometers, wind vanes, or anemometers; nor will instruments
be suppUed when the proposed station is considered too near others
aheady estabUshed.

Cooperative observers who fail to comply with the conditions upon
which Weather Bureau instruments have been issued wiQ be caUed
upon by the section director to return them.

Blank forms and franked envelopes are furnished free of expense to
the observers for transmitting reports to the section centers.

Observers willing to furnish the local press with meteorological
data for pubUcation wiU be suppUed with suitable postal-card forms,
properly addressed, upon appUcation to the section director.

The cooperative observer is requested to fill up and forward to the
section center, as soon as the equipment is installed, a copy of Form
No. 4029 Mis. (Description of Cooperative Observer's Station and
Instruments), and when any change is made in the location of instru-
ments to promptly notify the official in charge of the section center.

All correspondence relative to the work of a cooperative station
and requests for instruments, suppUes, etc., should be addressed to
the official in charge of the section center, who will furnish such infor-
mation as may be required and act promptly upon the requests.

I.— INSTRUCTIOirS FOR THE ERECTION AND CARE OF

INSTRUMENTS.

THE OBJECT OF TEMPERATURE READINGS AND THE EXPOSURE OF

THERMOMETERS.

1. Temperature of the air, — ^The use of thermometers m meteoro-
logical observations is for the purpose of obtaining the temperature
of the free air. It is very important to always bear in mind that the
actual temperature of the free air is the object of measurements.

INSTRUCTIONS FOB COOPEKATIVB OBSERVEES. 7

The air near the surface of the earth is nearly always in motion
more or less, and when not confined in a comparatively closed space
the several portions thoroughly intermingle with each other and
have nearly or quite the same temperature. When any portion of
the air is confined, however, so that it can not intermingle freely with
the general air masses, its temperature will be influenced to a marked
extent by the local surroundings and wiU not be a free-air temperature.

2. These ideas show us at once that if we mean to make observa-
tions of the real air temperatures our thermometers must, if possible,
be placed in a perfectly open space where the circulation of the air
is entirely unobstructed. It will not do, however, to place the ther-
mometers simply in the open air, exposed freely to the sky and the
direct rays of the sun. The sunshine would cause the thermometer
to register too high, and even if not exposed directly to the sun it
could not be depended upon to indicate the true air temperature
either day or night.

3. Thermometer shelter, — ^To overcome these difiiculties, it is neces-
sary to employ a thermometer shelter. This is nothing more than a
box with louvered sides made in such a way that the air can move
through it with the greatest possible freedom. This is an essential
condition in thermometer exposure. The object of the box or shelter
is simply to screen off the direct and reflected sunshine and the radia^-
tion to and from the sky, and to keep the thermometers dry.

To obtain the true air temperature, therefore, place aU thermome-
ters in a suitable shelter exposed in the open, or on a house top,
where the circulation of the air is as free as possible. When the
shelter can not be placed in a field or open space or on the top of a
house, it may be placed on the north side of some building. It
should not be placed on a building liable to be shaken, as jarring
tends to displace the index of the minimum thermometer and make
readings of that instrument erroneous.

A shelter of approved pattern on a short wooden support is shown
in the frontispiece, with a set of maximum and minimum thermome-
ters in correct position on the old wooden mounting. These old
style mountings are being replaced by Townsend supports,, shown in
Figures 7 and 8. The picture shows also the rain gage, but in order
to bring this into the picture it was placed nearer the shelter than it
should be in actual use. The rain gage should be at least 15 or 20
feet from the shelter.

4. Locks for instrument shelters. — For several years past aU shelters

issued to stations from the central office have been furnished with

the same kind of lock and key (known as the No. 8). This is the

, standard lock, and new keys can always be procured promptly on

application to the section center, where a small stock will be kept.

8 INSTRUCTIONS FOR COOPERATIVE OBSERVERS.

Prior to the adoption of the above No. 8 lock a so-called No. 9
lock was used for two or three years, and extra keys for this lock can
be obtained from the central office. Sections having trouble with
locks not of either of the above patterns should make appUcation for
the standard lock and key (No. 8).

5. SpecificatioTisfor shelters, — Owing to the cost of shipping shelters
to great distances, it is often economical to build shelters at destina-
tion. Copies of specifications and drawings can be obtained upon
appUcation to the Chief of the Weather Bureau.

6. Location or exposure of shelter. — The shelter should be set up,
whenever possible, over grass-covered ground and in an open, clear
space easily accessible to the observer, and about 4 feet above the
ground. Where such a location is not obtainable, however, the shelter
may be placed on the roof, or secured to the north wall of a building
by means of suitable screws through the back of the shelter, which
should be held 2 or 3 inches away from the waU by previously spiking
thick strips of wood thereon.

In aU cases the position of the shelter must be such that the door
opens to the north.

7. Installation of shelter, — Shelters sent to observers from the
central office are generally assembled complete ready to set up, but
the legs or supports of the shelter are not supphed; these can be
readily made up at station at small cost. The height of shelter
supports should be approximately 4 feet above the ground.

GENERAL DESCRIPTION OF THERMOMETERS.

Figure 1 shows the appearance of the maximum and minimum
thermometers when set up according to the standard method of
mounting on the old style wooden support.

The upper thermometer, occupying the horizontal position, is the
minimum and the lower is the maximum.

8. Before the observer attempts to set up the thermometers, let
him first examine them and compare them with the description and
famiharize himseK with all the pecuharities of each, so that he may
understand which is the maximum and which is the minimum.

9. Maximum thermometer, — ^The maximum thermometer is always
fiUed with mercury, sometimes called quicksilver.

The most distinctive pecuUarity of the maximum thermometer,
however, is not so easily seen. If the observer will hold the ther-
mometer vertically with the bulb down he will notice that the
mercurial column does not extend entirely into the bulb. A close
examination of the thermometer at the point just above the bulb
where the mercurial column stops will show that the glass tube
seems to have been almost closed at that point, in about the manner
shown in figure 1. This is just what has been done, and the passage-

INSraUCTIONS fob COOPEBATIVB 0B8EBVEBS. 9

way for the mercury is so fine at that point that the mercury will go
through only with some difficulty. The observer should next hold
his warm fingers around the bulb. The mercury in the bulb expand-
ing as it becomes warm will then be forced to pass the constricted
portion of the tube, flowing through in little spurts. When the
fingers are removed from the bulb, the mercury below the constric-
tion, contracting as it cools, withdraws toward the bulb, but none of
the mercury above the constriction goes back, and the length of the
column remains the same as it was when the bulb was warmest.
In this way the maximum temperature is registered.

10. Betreaters. — Experience has shown that in spite of every care
in the inspection and testing of maximum thermometers they will
sometimes fail to record the maximum temperature; that is to say,
the constriction in the bore of the tube is not so fine as required, and
when the temperature falls after reaching the maximum point the
mercury in the column of the thermometer withdraws into the bulb

ninimuni tbeimometers on old atyle board auppoit,

and the record of the maximum temperature is lost. Such ther-
mometers are sometimes said "to retreat," and are called "retreaters."

11. Erroneous temperatures due to this cause are almost entirely
avoided by mounting the thermometers as shown in Fig. 1, so that
the bulb of the maximum is higher than the stem. In this position
the column of mercury of the maximum thermometer breaks away
from the constriction to aqch an extent that it will rarely fail to
record the highest temperature reached.

The principal objection to this method of mounting, however, is
that the thermometer must be lowered to a vertical or nearly vertical
position before a reading can be made. This should be done care-
fully, especially in warm weather, as the weight of a long column of
mercury may force a portion through the constriction, thus leading
to an erroneous reading.

The bent wire pin should be carefully withdrawn and the ther-
mometer slowly lowered to the vertical position. The reading should
then be made.

After reading, the thermometer should be set by whirhng as
described in paragraph 25,

12. Minimum thermometer. — This thermometer, as used by the
Weather Bureau, is always filled with alcohol, and is therefore at

10 INSTRUCTIONS FOR COOPERATIVE OBSERVERS.

once distinguished from a mercurial thermometer. Besides the
alcohol there is inside the thermometer also a Uttle black object
having a rounded head on each end. This object is caUed the index
and is the prime characteristic by which this kind of minimuDi
thermometer is distinguished from all other thermometers.

13. Grenerally the index will sUde freely up and down the ther
mometer tube when one end is raised or lowered. Sometimes, how-
ever, and especially after the thermometer has been shipped, the
alcohol in the tube becomes broken up into short, detached columns
and the index is frequently caught and held.

14. Of course the thermometer can not be used until this is reme-
died, which in some cases proves to be a difficult operation. Observ-
ers are requested to use special care in learning and following the
instructions given below and to notice carefully the several eflFects so
that they may judge for themselves as to what need be done to unite
detached columns and avoid the danger of breaking the instrument.

INSTRUCTIONS FOR REUNITING DETACHED COLUMNS OF ALCOHOL.

15. The many different ways in which the alcohol column becomes
separated make it impossible to unite it by any single method,
different methods being required not only for different conditions
but also for different thermometers.

Frequently there are only a few short, detached portions near the
top, and the index sUdes freely along the lower portion of the tube
and drops into the bulb. Again, the detached columns are found
all along the tube, and the index is caught and held at some point
above the main column. In such a case it is advisable to first bring
the index into the bulb, as follows:

16. First process. — Hold the thermometer hghtly between the
thtimb and fingers and strike the lower end of the mefcaUic scale
against the top of a table or other firm object, as shown in figure 2;
first, however, interposing one or two thicknesses of cloth, or several
folds of paper, so as not to produce too severe a shock upon the
thermometer. The taps of the thermometer should be lightly made
at first, and the index examined to see if it has not moved along the
tube even a Uttle distance, as can be told by noticing the exact posi-
tion of the index in reference to the graduations on the tube. If
several taps fail to move the index, increase the force of the taps
a little at a time, imtil the index starts, after which repeat the opera-
tion imtil the index gets within the continuous column. Here it will
fall of its own weight into the bulb. Generally this will be all that is
necessary to place the index in the bulb. Sometimes the detached
columns wiU also have been partly or wholly united. If the column
is still broken in places the observer should try a few more taps, and

INSTRUCTIONS FOB COOPERATIVE OBSERVERS. 11

examine quickly in a very careful maimer. Small portions of the
alcohol will generally be seen slowly moving along the sides of the
tube toward the main column, and a continuation of the taps will
■unite the columns. In some cases 15 or 20 minutes may be required
to completely unite broken columns. If, however, the index can not
"be made to move with quite hard taps, or the columns can not be
united, it is advisable to try some of the methods described next,
"being careful always to avoid carryii^ any process so far as to en-
dai^er breaking the thermometer.

17. Second process. — ^This method will not loosen the index, but
may unite the detached columns. Grasp the thermometer securely a

little below the middle, with the bulb end down, and strike the edge of
the metal back opposite the broken column sharply against the fleshy
portion of the palm of the other hand, or, if necessary, against a small
block of wood held in the hand. (See fig. 3.) A continued jarring
in this way often causes the alcohol to run down, though in many
cases a large number of taps are necessary. Observers should there-
fore not give up if the colunm does not unite at once, but should
watch very closely for the movements of small portions of alcohol
along the sides of the tube. Here, again, care must be exercised not
to strike too hard, and to hold the thermometer by the metal back
in such a manner as not to squeeze or pre.ss against the stem of the

12 INSTHUCTIONS FOB COOPBRATIVB OBSEBVEBS,

thermometer itself. When the bore of the thermometer is large the
above process is almost sure to unite the column. Good results are
also obtained with thermometers of fine bore, though the latter, even
in skilled hands, often require a half hour or more of time if the
colimin is badly detached.

18. Third process. — ^This method can also be used in place of those
above, and is sometimes effective in forcing the index into the bulb.
Grasp the thermometer a httle above the middle, clasping the fingers
and hand firmly against the edges of the metallic back, but not so as
to bring any pressure upon the glass tube, which should be turned
toward you and with the bulb uppermost, as shown in figure 4. With
the thermometer in this position, and about as high as the head, and
the arm free from the body, quickly lower the arm and hand a foot or

more, turning the wrist at the same time, so that the bulb of (he
thermometer describes a somewhat circular path downward through
the air, stopping the motion with a sudden jerk just as the ther-
mometer is vertical. If the thermometer is grasped properly, a very
violent motion can be given in this way without dai^er. It will
sometimes be necessary to repeat the operation a great number of
times to entirely unite the detached columns.

19. Fourth process. — A modification of the swinging process just
described consists in whirling the thermometer rapidly on a short
string. For this purpose a stout string is passed through the hole
in the top of the metal back of the thennometer. This is left double
and firmly grasped at a distance of 6 or 8 inches from the thermome-
ter, which may then be given a very rapid whirling motion. Con-
siderable care and practice are required to whirl the thermometer

INSTBtrCTIONS FOB COOPEBATIVE OBSEBVBHB. 13

rapidly and stop it safely. This metbod will, however, often brii^
down the index and unite detached columns.

20. If observers are unsuccessful after caret'nlly following the above
tnstmct'.ons, the matter should be reported to the section center,
givii^ full particulars as to what has been done.

21. Testing minimum thermometer. —Some one or more of these
procesaes should in nearly all instances be sufficient to unite any
detached column, and when all the bubbles have been removed the
observer can then see how the instrument works. Hold the ther-

mometer vertically and warm up the bulb by holding it in the hand;
then turn the instrument upside down. Watch the index as it glides
along the tube; when it strikes the top of the column it will at once
stop. This operation of bringing the index to the top of the column
is called "setting" the thermometer.

Next hold the thermometer horizontally. Aa the bulb cools off
the index will be dragged backward toward the bulb, but always
remains at the end of the column of alcohol. It is a good plan to
hasten the cooling by placing a little wet cloth or piece of ice against
the .bulb. When you have watched the index go down with the
column, warm the bulb again with the hand. The column will go up
immediately, but the alcohol will flow around the index and leave

INSTRUCTIONS FOR COOPERATIVE OBSERVERS.

it at the lowest point; that is, the index remains so that its top end
is at the lowest point reached by the alcohol column, and the mini-
mum temperature is indicated in this way. The thermometer must
be held horizontally throughout these operations.

When the thermometer is not in use for observation, it is a good
plan to hang it up, as bubbles are less likely to form in the tube in
this position.

The thermometer should also be maintained in a vertical position
for several hours after a broken column has been united to permit
any alcohol clinging to the sides of the bore to drain down.

INSTRUCTIONS FOR MOUNTING MAXIMUM AND MINIMUM THERMOMETERS.

22. The style of wooden support shown in figures 1, 5, and 6, while
in use at many of the oldest stations, is being replaced by the so-called

Fig. 5.

Fig. 5. — Illustrating setting of Tnayimiim ther-
mometer by whirling on wooden support.

Fig. 6.

Fig. 6. — Illustrating setting of minimiun ther-
mometer by turning it to an inverted position
imtil the index falls to the end of the column.

Townsend support, shown in figures 7 and 8. The use of the wooden
support will be sufficiently understood, it is believed, from the figures
without detailed instructions.

23. TTie Townsend thermometer support. — This support, with ther-
mometers attached, shown in figures 7 and 8, should be firmly
screwed to the cross board of the instrument shelter, approximately
in the middle, and with the legend ^^U. S. W. B.'' right side up.

24. Maximum tJiermometer. — Mount the maximum thermometer
on the carrier on the long projection stud, and clamp it somewhat
above the middle point of the scale and with the bulb at the left, so
that it overbalances and tends to hang bulb end down.

25. To whirl and set the maximum thermometer. — ^Release the pawl
fixed near the base of the maximum pin. This unlocks the carrier.

INSTRUCTIONS FOE COOPEBATIVE OBSEHVEES. 15

Place the finger, or pencil, at one side of the thermometer scale and
impart to it a rapid rotation, tis suggested by the dotted line and
arrow in figure 8, Allow the thermometer to whirl until it comes to
rest itself. Do not try to stop it while whirling. Note carefully
whether or not the space between the bulb and constriction is filled
with mercury. Repeat the whirling, if necessary, until the column is
whirled down as far as it can go.

Engage the pawl again and carefully elevate the bulb end of the
thermometer until the pawl catches and holds the carrier. The
thermometer is now "set" and ready to indicate the ensuing maxi-
mum temperature.

26. The revolving carrier for the maximum thermometer must be
oiled occasionally, through the hole in the side provided for the pur-

Fia. 7. — TheTmamfiteraupports,Townsend pattern.

pose, so that the carrier will revolve easily. A fluid, nongumming
oil should be used.

Attention is invited to the fact that maximum thermometers
purchased by the bureau under contracts dating from July 1, 1913,
are not fitted with brass hubs for mounting and whirling the same, as
used with the so-called "old-style" supports. Therefore, where a
cooperative or other station has the old brass supports for maximum
and minimum thermometers in use, and the new pattern maximum
thermometer is suppUed, it is necessary, also, to replace the supports
with the "Townsend" pattern, illustrated in figures 7 and 8, obtain-
able on "Stores" requisition in the usual manner.

27. To read t^e maximum thermometer.— First carefully disengage
the pin or pawl that holds the maximum thermometer in a horizontal
position, then slowly lower it, bulb end down. The thermometer
must not be lowered to tho vertical suddenly, especially in warm
weather, as tho weight of the long column of mercury is likely to
force some portion through the constriction and cause an erroneous
reading. The maximum temperature is the scale reading at the top of
the column of mercury.

16 INSTRUCTIONS FOB COOPEEATIVE OBSEHVEES.

28. Mounting minimum thermometer. — The m inimum' thermometer
must be mounted upon the carrier on the short projecting stud.
Clamp the thermometer in the carrier at about the middle point,
with the hilb end to the left.

29. To set the minimum iherTnometer. — ^Tum the carrier and ther-
mometer to a vertical position, bulb uppermost, and allow the index
to fall to the end of the column. After setting do not fail to turn the

Flo. 8.— ThermameUr supports. Fawl dissugBged, maiimiua rotating.

1 thermometer back to its horizontal position as shown in
figures 1, 7, and 8.

30. To read the minimum thermometer. — The minimum thermometer
must always be read while it is still in its horizontal" position as left
after setting at the previous observation. To avoid possible dis-
placement by vibrations, the min imum thermometer must be read
before whirhng and setting the maximum thcrmonietor. The read-
ing is obtained by noting the number of tiegrees on the scale opposite
the end of the index farthest from, the bulh. A reading taken at the end
of the spirit column will give the current temperature.

INSTRUCTIONS FOR COOPERATIVE OBSERVERS. IT

31. If at any time the column is found to be broken and bubbles'
are observed in the tube the instrument should be taken off the
supports and an effort made to unite the column by some of the
methods already described.

THE RAIN OAOE.

32. The exposure of the rain gago is a very important matter.
The most serious disturbing effect in collecting rainfall is the wind.
In blowing against the gage the eddies of wind formed about the
mouth tend to carry the rain away, so that frequently too Uttle is
caught in the gage.

Observers will therefore take particular care in selecting a place
for the location of the gage, as the value of the records is sometimes
greatly impaired by improper exposure. It is scarcely necessary to
say that every precaution should be taken to protect gages from the
interference of animals and unauthorized persons. Select, if possible,
a position in sonle open lot„unobstructed by large trees, buildings, or
fences. Low bushes and fences, or walls that break the force of the
wind in the vicinity of the gage, are, however, beneficial, if at a dis-
tance at least as great as the height of the object. Such surroundings,
in general, afford the best exposure. Gages should be exposed upon
roofs of buildings only when ground exposures are impracticable, and
then the roof should be flat, or nearly so, and the middle portion
should be selected to get the best results.

33. Rain gages in sUghtly different positions, if badly exposed,
catch very different amounts of rainfall. Within a few yards of each
other two gages may show a difference of 20 per cent in the fall
in a heavy rainstorm. The stronger the wind the greater the differ-
ence is apt to be. In a high location eddies of wind produced by
walls oi buildings divert rain that would otherwise fall in the gage.
A gage near the edge of the roof, on the windward side of a building,
shows less rainfall than one in the center of the roof. The vertical
ascending current along the side of the wall extends shghtly above the

'level of the roof, and part of the rain is carried away from the gage.
In the center of a large, flat roof, at least 60 feet square, the rainfall
collected by a gage does not differ materially from that collected at
the level of the ground.

34. Description of rain gage. — ^The rain gage consists of the following

parts:

The receiver A;

The overflow attachment B;

The measuring tube C.

The top cylindrical portion of the receiver, marked a in fig. 9, is

exactly 8 inches in diameter, inside, and is provided with a funnel-

71982'— 15 3

INSTRUCTIONS FOB COOPERATIVE 0BSEEVEB8.

shaped bottom, which conducts any precipitation caught in the
receiver into the tall cylindrical measuring tube, C, the total height
of which, inside, is exactly 20 inches. The diameter of this tube is
much smaller than the large receiving tube, a, being only 2.53 inches.
In consequence of this a small amount of rain falling into the receiver
and flowing into f fills the latter to a depth greater than the actual
rainfall in proportion as the area of the receiver is greater than the
area of the measuring tube. In the standard gages of the Weather
Bureau the depth of the rainfall, in accordance with this principle, is
magnified just 10 times. The receiver, A, has a sleeve, d, fig. 9,

ri'ant n«u'.

Vertical Secttark

JTorixanMl Seutian.^R

which shps over the tube, C, and very effectually prevents any loss of
rainfall. Again, when the rainfall is very heavy the tube, C, may
overflow. In this case, to prevent loss, a Uttle opening, shown at
e, fig. 9, is made in the sleeve, d, just on a level with the top of the
tube, C. The excess of rainfall escapes through this opening, and
is retained in the large overflow attachment, B, and can be measured
afterwards, as will be described later. The opening e is omitted in,
the latest forms of gages, as the water easily flows between the sleeve
and the tube C which fit each other loosely. The inside diameter
of the overflow attachment is just 8 inches, and this portion of the
instrument can be iised as a snow gage, as will be explained hereafter.

INSTHUGTIONS FOR COOPEBATIVB 0BSERVBB3. 19

35. Bain-gage support.— Th.Q box in which the gage is shipped to
the observer is expressly designed as a stand for the instrument and
should be opened at the head, which is fastened by screws. Set the
box as nearly vertical as possible at the place selected for the ex-
posure and secure it in this position by driving down four stakes
alongside, in the manner indicated in %. 10. Care must be taken
to have the gage held in a truly vertical position. Slip in the head
and lower it to the level of the screw holes in the sides of the box
about 10 inches from the bottom, where the head will be securely

Fia. JO,— Ralo gsgo tuid support.

fastened with the screws taken out in opening the box. The g^a
can now be placed inside, and appears as shown in figure 10.

HOW TO MEA8UBE RAINFALL AND SNOWFALL.

36. RainfaU. — The measuring stick of the rain gage is graduated
into inches and tenths. Remembering that the actual depth of the
rainfall is magnified ten times, as explained above, it is plain that if
we find the water 10 inches deep in the measuring tube, then the
actual rainfall must have been only 1 inch deep, or if the water in
the tube b only one-tenth inch (or written as a decimal, 0.1 inch) deep,
then the rainfall must have been only one-hundredth inch (or written
aa a decimal, 0.01 inch).

20 INSTRUCTIONS FOR COOPERATIVE OBSERVERS.

37. The depth of the water is measured by inserting the measuring
stick into the gage through the small hole in the funnel. "When the
stick reaches the bottom of the measuring tube it should be held for
one or two seconds, and then quickly withdrawn and examined to see
at what division of the graduation the top of the wet portion conies.
The numbering of this division, as stamped on the sticky gives, as has
just been explained, the actual depth of rainfall, and in making out
records and reports observers should always use the decimal expressions.

38. After measuring and recording in this way the precipitation
found in the gage, the top should be removed, the measuring tuTbe
emptied and drained, and the gage put in position again. Observers
should be careful, after emptying the gage, to replace the measuring
tube so that the bottom stands within the ring in the middle of the
bottom of the overflow, and in putting on the receiver that it passes
over the measuring tube and rests squarely down upon the overflo'w.

39. "When the amount of rain that has fallen more than fills the
measuring tube, some care is required to determine the total rainfall.
First carefully remove the receiver so as not to spill any of the water
in the measuring tube, which should be exactly full. If some water
has been slopped out and the measuring tube is not exactly full, the
amount of water remaining must be accurately measured with the
stick, as abeady described. The tube is then lifted out slowly and
carefuUy, so as not to spill any of the water into the overflow, emptied,
and allowed to drain a moment or so. The water remaining in the
overflow is now poured into the measuring tube, care being taken not
to lose any, and measured in the usual way. Suppose we find this to
be 0.47 inch rainfall, then, remembering that the measuring tube is
just 20 inches high, the total rainfall will be 2 inches + 0.47 inch = 2.47
inches. Or, in case some water was spilled from the measuring tube,
the 0.47 inch should be simply added to the first measured amount
to give the total rainfall.

40. Snowfall. — ^During the winter season, especially in those cli-
mates where the precipitation is nearly all in the form of snow, the
overflow attachment only of the rain gage should be exposed in the
support as a snow gage. Remove the receiver and measuring tube to
the house, as these parts can not be used for measuring snow, and even
if rain should occur it is very apt to be frozen while in the measuring
tube, generally bursting it and rendering it worthless or highly
inaccurate.

41. First Tnethod. — ^The snowfall collected in the overflow attach-
ment is measured after placing the vessel in a warm room until the
snow is melted. The water is then carefuUy poured into the measur-
ing tube and measured just as though it were rainfall.

42. Second method, — ^The first method is objectionable, l;>ecause it
often requires considerable time, and is Uable to be inaccurate, owing

INSTRUCTIONS FOB COOPERATIVE OBSERVERS. 21

to the loss of the snow or water by evaporation. The following plan
is much better, unless clumsily conducted so as to spill and waste the
water: Take the overflow into the room and pour into it, carefully,
OTie measuring tube fuU to the brim with water, preferably warm water.
This, in general, will mostly melt, or at least, reduce to a very fluid
slush, a considerable snowfall. The measuring tube should be again
carefully fiUed to the brim from the melted contents of the overflow
and emptied ; whereupon the remaining water in the overflow should
be carefully measured in the measuring tube, thus giving quickly and
easily the depth of melted snow.

43. The amount of snow collected in the overflow of the rain gage
is likely to be greatly deficient when the wind blows during the snow-
fall. In such cases it will be much better if the observer wiU discard
the snowfall in the overflow, empty it out and cut out a section of
the snow in an open place where the depth truly represents the
precipitation. This section is to be taken by plunging the empty
overflow, mouth downward, in the snow so as to cut out a cylindrical
portion the size of the overflow and the depth of the snow. By the
use of a thin board or other means it will not be difiicult to gather up
the complete section of snow inside the overflow, after which it should
be reduced to slush and measured as already exolained.

GENERAL INSTRUCTIONS ABOUT INSTRUMENTS.

44. Shipment of thermometers. — The wooden boxes and packing
material received with thermometers should be carefully preserved
for use in returning instruments.

In packing thermometers for transportation each instrument must
be carefully wrapped in sheet cotton; the whole surrounded with
excelsior or similar packing material, and, to prevent shifting, no
vacant spaces whatever should be left in the box. The lid of the
wooden box should always be secured with screws, as the jarring
resulting from driving nails into the wood is liable to break the
thermometers.

45. Use of ivory Hack, — ^When, from action of the weather and long
exposure, the graduation marks, figures, or lettering on the glass tube,
enamel scale, or metallic back of a thermometer are obht^rated or
illegible, they can easily be renewed by the apphcation of a small
quantity of artists' black pigment (ivory black). The best method of
applying the substance is to put a drop on a small stick, such as a
match, and rub it across the marks or lettering until the spaces are
thoroughly filled. The superfluous pigment should then be wiped
off with a piece of tissue or blotting paper in such manner as not
to draw the pigment from the lines.

46. Action to take when instruments are broken. — When from any
cause instruments are broken they should be promptly returned,
with an explanation, to the section center.

22 I15fSTEUCTI0NS FOR COOPERATIVE OBSERVERS.

Ordinary precautions arc required in the use of instruments, and
observers are requested to use every reasonable care to avoid acci-
dents, breakage, and loss.

n.— TO HAKE Aim BECOBD OBSEBVATIONS.

47. Observations desired. — It is requested that cooperative observers
make and record, daily, observations of the maximum and minimum
temperatures; precipitation (rainfall or snowfall); the state of the
weather — that is, the general character of the day from sunrise to
sunset; and such other miscellaneous phenomena as frost, coronas,
thunderstorms, tornadoes, and am-oras.

Form 1009, furnished by the section centers, is arranged to facilitate
recording the data desired by the Weather Bureau.

48. Time of making observations. — But one observation in each
24 hours is necessary on the part of cooperative observers, since the
average of the readings of the maximum and minimum thermometers
gives an approximately correct mean temperature for the day.

Uniformity as to time of taking observations is desired. A definite
hour should be determined upon and the observations made each day
as near that hour as possible. About sunset is recommended as the
most satisfactory time for making the record, as the thermometers
will then, except under unusual conditions, register both the maxi-
mum and the minimum temperatures for the day. The time at which
observations are taken should invariably be noted on Form No. 1009.

49. Form 1009, meteorological monthly record. — ^At the end of this
pamphlet will be found a copy of the form used by cooperative observ-
ers for recording observations, with data properly filled in, to show
how observations should be recorded.

It is particularly important, in the interest of accuracy, that tho
observations be recorded as soon as made, and that the entries bo
made day by day as observed. Even if no raiu has fallen, the observer
should bear in mind that his official record of that fact is as important
as the record of rainfall.

Special care should be exercised in the preparation of reports;
pencils should be kept sharp, and good carbon paper used to insure
satisfactory duphcate copies. Three copies of the report should be
made, one to be retained by the observer and two to be sent to the
section center on the first of each month. To make three copies of
the record requires two carbon sheets; these should be placed between,
the forms, carbon side facing the form on which the record is to be
made, and an ordinary pencil — one not too soft — used in writing.
If a mistake occms in recording attempt should not be made to writ©
over the figures; draw a line through the incorrect entry and mako
new figiu'es either to the right or left, or on the margin of the form.

INSTRUCTIONS FOB COOPERATIVE OBSERVERS. 23

When the carbon paper no longer makes clear duplicates ask for a
new supply. It is the wish of the Chief of the Weather Bureau to
keep cooperative observers well supplied with aU material pertaining
to their oflBcial duties, and they are requested to make timely requisi-
tions therefor on their respective section centers.

When the name of the station and its post oflBce are not the same
toth shoidd always be entered on Form No. 1009, fcho name of the
station at the top of the form, and any change in location or name
of the station should be explained by note.

TEMPERATURE RECORDS.

50. The readings of the maximum and minimum thermometers
should be made as explained in paragraphs 27 and 30 and recorded in
the appropriate columns of Form 1009.

In recording maximum and minimum temperatures the following
should be borne in mind. The maximum temperature of any day
can not he lower than any of the following readings: (1) The minimum
of the previous day; (2) the minimum of the same day; (3) the mini-
mum of the following day; (4) the set maximum of the preceding
day; (5) the set maximum of the same day.

The minimum temperature of any day can not he higher than
(G) the maximum of the preceding day, (7) the maximum of same
day, (8) the maximum of the following day, (9*) the set maximum
of the day before, (10) the set maximum of the same day.

51. Thermometers set. — Immediately after the thermometers have
been carefully read and the values noted on the form, they should be
set, first noticing, however, that both thermometers are in their
proper position and are securely fastened to their supports.

The maximum should be whirled and set first, and the minimum
next. In no case should the thermometers be set, except once ea^h
day, just after making the observation.

52. Test. — ^After setting the thermometers the readings of the top
end of the index of the minimum thermometer and the top of the
mercurial column of the maximum should give one and the same
temperature within a fraction of a degree. If the difference is a
degree or more, and it can not be corrected by resetting, it is possibly
due to bubbles in the minimum thermometer or shght displacements
of the alcohol. Persistent discrepancies of this sort should be
reported to the section center, and observers are requested to. have
this test in mind and apply it frequently in order to detect this
source of inaccurate records.

53. Plus and minus signs, — ^Temperatures below zero are written
with the minus sign prefixed, thus: —1, —2, —4, etc., all indicate
that the temperature is below zero. If the temperature is exactly

24 INSTRUCTIONS FOB COOPERATIVE OBSERVERS.

zero it should be recorded 0. Temperatures above zero are recorded
simply 2, 45, etc., as the case may be, it being understood by the
absence of any sign that it is plus (+), or above zero.

In determining means when there are minus (below zero) tempera-
tures, the sum of the minus readings must be deducted from the
sum of the plus readings and the remainder divided by the number
of days in the month, unless one or more days' records are missing,
when, of course, those missing days must be deducted from the
divisor.

If the sum of the minus readings is greater than the sum of the
plus readings, the latter should be subtracted from the former and
the remainder divided, as above. The resulting mean is, of course,
a minus temperature.

Observers not provided with self-registering thermometers and
using the exposed thermometer should alter the headings of the
first two, three, or four columns on Form No. 1009 to indicate the
hours at which observations are made and enter the readings accord-
ingly.

54. Shelter locked, — The shelter should be carefully locked after
taking each observation in order to prevent unauthorized persons
from interfering with the instruments.

, PRECIPITATION RECORDS.

55. Rainfall. — ^Measurements of rainfall should be made at the
time of regular observations, and the gage should be emptied of all
the water it may contain as soon as it has been measured and the
parts replaced in readiness for the collection of the next rainfall.
The amount of rainfall will be determined as explained in paragraphs
37, 38, and 39.

56. Snowfall. — Snowfall is preferably measured as depth of water
rather than by the thickness of layer it forms on the ground. When
it can not be measured accurately by melting, it is customary to take
one-tenth the measured depth of the snowfall on a level open place
as the water equivalent of the snowfall. The relation between the
depth of snow and depth of melted snow is very different in different
cases, depending on the wetness of the snow. The equivalent depth
of water in some cases is as great as one-seventh of the depth of snow,
and in others only one thirty-fourth. It is always best to reduce
snow to a liquid condition for measurement, and the simplest way to
do this is to add to it a known volume of water sufficient to reduce it
to a state of slush, as explained in paragraph 42. For each entry in
the column headed "Snowfall" there must be an entry in the cohimn
"Amount." For rainfall but one entry is made; for snowfall two,
one of which is the depth of the snow, the other the depth of the
water obtained by melting the snow.

INSTRUCTIONS FOR COOPERATIVE OBSERVERS. 25

57. In the winter season the overflow only of the gage should be
exposed, as stated in paragraph 40, and the snow collected therein
between observations (or, better, a section of snow cut out as
explained in paragraph 43) should be reduced to a state of slush and
measured in the manner described in paragraph 42.

58. In addition to this measurement by the gage a measurement
will be made of the actual depth in inches of the snow on the ground.
Select a level place of some extent, where the drifting is least pro-
nounced, and measure the snow in at least three places. The mean of
these measurements will give the snowfall, which is to be entered in
the column of the report headed "Depth of snowfall in inches,'' and
whenever it is impracticable to melt the snow, as described in the pre-
ceding paragraph one-tenth of this mean will give an approximate
value in water for the snow which could not be melted. This value
must be set down in the proper column of the report in precisely the
same manner as rainfall or snow melted in the gage. After having
once made a measurement of the snowfall, it is not desired that the
same snow be measured at each succeeding observation until it shall
finally disappear, except to get the actual depth of the snow on
ground for entry in the proper column. Any fresh snow, however,
should be measured and recorded after it falls.

59. If no rain, snow, or hail has fallen since the last observation,
make the entry 0.00 in the proper column. If the amount is too small
to measure, make the entry ''Trace'' or ''T."

MISCELLANEOUS PHENOMENA.

60. Frost — Occurrence of first and last frost of the growing season
should be specially noted.

The terms descriptive of frost will be as follows:

Lightf to indicate a frost that has no destructive effect, although
tender plants and vines in exposed places may be injured. Heavy j to
indicate a frost that in itself is severer than a light frost — ^that is,
the deposit of frost is heavier and the temperature falls to a lower
point, although the staple products of the locality may not have been
generally destroyed. KiUingy to indicate a frost that is generally
destructive of vegetation and the staple products of the locality.

61. Coronas. — ^These must be distinguished from halos. Coronas
are small circles, very commonly seen around the moon, due to rays
of light passing through a thin layer of cloud. Sometimes as many
as three small concentric circles may be seen whose diameters are
in the ratio of 1:2:3. They are frequently colored, red being the
outside color. These colors are not the pure colors of the spec-
trum, but rather those of the opal, and are caused by interference
and not refraction. A solar corona is not often visible, on account
of the dazzling brightness of the sun, but it may often be seen by

26 INSTRUCTIONS FOR COOPERATIVE OBSERVERS.

viewing the sun through colored glass, or noticing its reflection in
water.

62. Halos are large circles of about 45^ or 90° in diameter — that is,
the diameter is equal to one-eighth or one-fourth the circimiference
of the horizon. The colors are very feeble; the red is the inside
color. Halos arise from the presence in the atmosphere of minute
prisms of ice, and are due to refraction of light. Sometimes the halo
is intensified into two bright spots, one on each side of the central
limiinary. These are called "parheUa'' or ''paraselensB" (mock suns
or mock moons), sometimes sim-dogs. Still more compUcated opti-
cal phenomena are sometimes seen, though rarely, except in high
latitudes.

63. Thunderstorms. — Thimderstorms six hours apart may be con-
sidered as separate storms.

Upon the occurrence of thimder, give as nearly as possible the
times of first and loudest thimder and its duration, being careful to
note if a. m. or p. m.

Give the direction from which the storm appears to be coming, as
shown by threatening sky, hghtning flashes, or thunder peaJs. Also
the direction toward which it goes.

64. Tornadoes. — All the meteorological circumstances attending
these should be minutely noted, viz, the form and color of the clouds;
the direction and intensity of the wind; the frequency, intensity, and
form of the lightning; the occurrence of haU, destructive effects, etc.

65. Auroras. — ^The date, hour, and minute of the beginning and
ending of auroras should be carefully noted, as well as the azimuth
of the base and the altitude of the extremity, and of the crown of any
arch of light.

When the observer is familiar with the names of the principal
fixed stars, he may locate the arch or crown by reference to them,
but it is preferable that he should observe directly the altitude and
azimuth.

Observers should be particular as to the date of the aurora; and
when it begins in the evening of one day and continues into the early
morning of the next day, it will be entered as occurring on the^rs^
day, but its details will be given in the record as occurring between
the hours of its actual beginning and ending. Thus, an aurora that
began on the evening of the 12th of January and continued xmtil the
early morning of the 13th would be entered as the aurora of the 12th.,
but its details would be recorded as occurring, for instance, between
the hours of 10 p. m. of January 12 and 2 a. m. of January 13.

66. General pJienomena of climate, — Information of a general char-
acter relating to the growth of plants will be of value in determining
the climatology of a district,

INSTRUCTIONS FOR COOPERATIVE OBSERVERS. 27

67. Character of the day, — ^The general character of the day from
sunrise to sunset should be recorded as '' clear/' when the sky averages
three-tenths or less obscured; partly cloudy, when from four-tenths to
seven-tenths obscured; and cloudy, when more than seven-tenths
obscured. The average cloudiness from sunrise to sunset may be esti-
mated with considerable accuracy by noting the degree of cloudiness,
on the scale given, as near simrise as possible, between noon and 1
p. m., and near sunset; add these and divide this sum by 3; the
quotient will be considered the average cloudiness.

When light fog, light haze, or light smoke has prevailed during the
greater part of the day, with three-tenths or less of clouds, its character
should be recorded as "clear,'' but when dense fog, dense haze, or
dense smoke has prevailed the character of the day should be recorded
as '^ foggy," ''hazy," or ''smoky," as the case may be. When the last-
named conditions prevail, it is recommended that observers note in
the column headed "Miscellaneous phenomena" the duration of same,
e. g., "dense fog from early morning till 3.00 p. m.," etc.

NOMENCLATURE.

68. The great diversity in the usage of meteorological terms by
the daily press and meteorological observers makes it desirable to
adhere to the following:

The word "storm" will refer to a disturbance of the ordinary
average conditions or to unusual phenomena, and imless specifically
qualified may include any or all meteorological disturbances, such as
wind, rain, snow, hail, thunder, etc. This word may be qualified by
some peculiarity, e. g., sand storm, or dust storm (such as the
"simoom"), hot wind (such as the "khamsin," "foehn," or "chi-
nook"), cold windstorm (such as the "norther" and the "pampero"),
cold rainstorm and snowstorm (such as the "blizzard").

69. A hurricane or "typhoon" is a large storm, often several hun-
dred miles in diameter, within which violent winds circulate around
a center. The center of a hurricane or "typhoon" is a compara-
tively calm region, where sometimes the clouds break away and the
rain ceases; whereas the center of a thimderstorm is the region of
greatest intensity of wind, rain, or lightning.

28 INSTRUCTIONS FOB COOPERATIVE OBSERVERS.

as in the "derecho/' or straight-line wind, or which have a quasi-
rotation aroxind a horizontal axis, as in the blast that accompanies
the front of a ''norther'' or the gust in front of the heavy rain of a
thunderstorm. Endeavor should be made as far as possible to sepa-
rate the true tornado, which is rare, from the numerous destructive
winds, squalls, and gusts, which are frequently called tornadoes, hurri-
canes, cyclones, and other high-sounding names.

71. The term ''whirlwind" is applied to any revolving mass of
air, and includes at one extreme the hurricane and at the other
extreme the dust whirl of our street comers.

72. A "cyclone'' is a mass of air circulating around a center. The
lower portion of the air near the earth's surface has a vorticose move-
ment toward a center, while the upper layers have a movement
from a center. The line joining the upper and lower centers is
the axis of the cyclone. The direction of rotation is the same in
both upper and lower layers. In the Northern Hemisphere this
rotation is said to be in a negative direction, or opposite to the
diurnal motion of the sun in azimuth, and opposite to the movement
of the hands of a watch lying with its face uppermost.

73. An "anticyclone" also is a mass of air circulating around a
center, but the lower layer of air has a movement out from a center
and the direction of rotation is opposite to that of a cyclone, being
positive in the Northern Hemisphere.

74. The terms "cyclone" and "anticyclone" describes phenomena
that can not be observed at a single station. They should therefore
not be used in the description of local phenomena; they represent
generalizations based upon the charting and study of winds and
clouds observed at many stations, and should only be used when the
nature of the rotation of the winds has been clearly demonstrated
or can be safely inferred.

75. The terms "cyclonic winds," "cyclonic system," and "cyclonic
rotation" are equivalent to "cyclone." The outer portion of a
cyclone generally has feeble winds and fair weather.

76. The terms "high" and "low" refer to areas in which baro-
metric pressure is above or below that of the surrounding country,
without reference to any normal values and without implying any
specific peculiarity as to winds or weather.

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INSTRUCTIONS FOB COOPERATIVE OBSERVERS. 31

III.— EAETHQXTAKES AND IirSTEXTCTIOirS FOE THEIE NONIir-

STEUMENTAL OBSEEVATION.

IMPORTANCE OF EARTHQUAKE DATA.

77. While really destructive earthquakes are unusual, only a few
occurring during the course of a year in any part of the world, tremors
strong enough to produce slight damage occur somewhere every few
days. Indeed, if we count all disturbances from the most destructive
to the feeblest it would appear that the earth is seldom, if ever,
wholly at rest.

78. Some portions of the earth's surface are, as is well known, far
more frequently visited by earthquakes, both great and small, than
are certain others, but no place is entirely fre© from at least an occa-
sional shock. Hence, seismology, or the science of earthquakes and
their phenomena, is of some importance to every one and of great
importance to many. Thus, to be specific, and to confine attention
strictly to the obviously and eminently practical, we should know
the exact locations of those numerous breaks and weak vertical
seams in the earth's crust along which abrupt slipping and sliding
(the cause of nearly all earthquakes) most frequently occur, so that,
as far as possible, we may avoid them in the location of such perma-
nent structures as dams, irrigation channels, aqueducts, bridges, and
even ordinary houses.

WHY THE WEATHER BUREAU SHOUTJ> COLLECT EARTHQUAKE DATA.

79. In spite of the good it clearly would serve, there is, however,
no map of any country that gives at all fully the locations of earth-
quake breaks or faults, nor is the collection of the data essential to the
construction of such a map of any extensive section possible, except
through the long and constant cooperation of a large number of
observers widely scattered over the area in question.

80. If then the people of the United States are to be supplied with
such practical maps as would enable then to reduce to a minimum
their fears of and losses from earthquake disasters, the necessary data
obviously may most easily be collected by the Weather Bureau, since
it alone, of the various Federal scientific institutions, already has the
adequate personnel and necessary organization.

REQUEST FOR COOPERATIVE OBSERVERS.

81. Although each of the Weather Bureau's regular stations,
approximately 200, will report all earthquakes felt, yet the territory
covered is so great that its seismic disturbances can not adequately be
recorded without the aid of a large number of voluntary assistants.
Hence it is earnestly hoped that, so far as possible, all the bureau's

32 INSTRUCTIONS FOR COOPERATIVE OBSERVERS.

numerous cooperative observers will assist also in the collection of
seismologies! data, by reporting, on cards that will be furnished for
that purpose, the date, etc., of each earthquake that they may
experience. To each observer the labor will be exceedingly light,
and the time consumed only a few minutes in a whole year, but the
collected results will be permanent and extremely valuable — abso-
lutely essential to the construction of the maps in question and
exceedingly helpful in the explanation of many obscure earthquake
phenomena.

INSTRUCTIONS FOR THE COLLECTION OF EARTHQUAKE DATA.

82. The particular earthquake data desired is indicated on the
question cards that will be supphed to all who take part in this work,
but the method of collecting and forwarding this information to the
central office for classification and study is explained by the following
instructions:

(1) Regular Weather Bureau stations will be communicated with
directly from the central office; cooperative stations entirely by, or,
when necessary, through section centers.

(2) All routine communications on seismology directed to the
central office will be inclosed in penalty envelopes marked ''Seis-
mology.''

(3) Each regular Weather Bureau station and each cooperative
station that agrees to assist in this work will be furnished with a
supply of question cards.

(4) Each station, regular and assisting cooperative, will promptly
fill out and forward in a penalty envelope one question card for each
earthquake felt.

(5) The regular stations at Boston, Atlanta, St. Louis, Denver, and
San Francisco will also send to the central office such newspaper
clippings in regard to earthquakes in the United States as may come
to their notice.

(6) Each section center may supply question cards to other
rehable persons in addition to the cooperative observers. This is
especially desirable in those portions of the country which are either
subject to earthquake shocks or sparsely inhabited.

(7) An earthquake that produces any appreciable damage will be
made the subject of a special investigation determined upon at the
time.

(8) All question cards collected by section centers recording the
occurrence of an earthquake will be promptly forwarded to the
central office.

INDEX.

Subjects. Paragraph.
Address of station 49

Air, temperature of 1

Alcohol, in minimum thermometers 12

column detached 13.14,15,31

reuniting column 16, 17, 18, 19

Anticyclone 73, 74

Auroras 47 , 65

Black pigment fof thermometers 45

"BHzzard" 68

Boxes, for shipping thermometers 44

Box support, for rain gage 35

Broken instruments, returning of 46

Bubbles in minimum thermometers 31

prevented by hanging up 21

reuniting column 16, 17, 18, 19

Carbon sheets for making records 49

Cards for reporting earthquakes 81, 82

forwarding to central office 82

Catch of rain gage 33

"Chinook" 68

Climate, general phenomena of 66

Clippings, newspaper, of earthquakes 82

Constriction in maximum thermometers 9

Cooperative observer's meteorological record 47

Coronas 47, 61

Correcting mistakes in meteorological record 49

Communication with cooperative observers, conducting 82

Communications on seismology with central office, addressing 82

Clouds 67

Cyclone 72, 74, 75

Daily meteorological observations 47

Day, character of 67

Data comprising meteorological observations 47

earthquake observations 82

Defective maximum thermometers, " retreaters " 10

minimum thermometers, broken alcohol columns 13, 14, 15, 31

reuniting alcohol columns 16, 17, 18, 19

"Derecho" 70

Diameter of rain-gage receiver 34

tube 34

Discrepancies in readings of thermometers 52

"Dust storm" 68

Duties of making earthquake observations 81

Earthquake data 77 to 82

from outside sources 82

Earthquake districts, location of 78, 79, 80

34 INDEX.

Paragraph.

Earthquakes, importance of cooperative observationfl 81

intensity of 77

of appreciable damage .* 82

Erroneous temperatures, guarding against 11

Exposure of rain gage 3, 32

instrument shelter 3

thermometers 2

"Foehn" 68

Fog 67

Form 1009 Metl. (Observer's record) 49

Frost 47,60

light 60

heavy 60

kilhng 60

Funnel of rain gage 34

Gage, rain, catch of 33

description of 34

distance from shelter 3

exposure of 32

size of 34

snow, description of 34

Graduation marks, renewal of on thermometers 45

Gusts 70

Hail 64

Halos 62

Haze 67

"High" 76

Hurricane 69

Index of minimum thermometers 12

reading of 30

sticking of 13

Instruments, broken, returning of 46

Ivory black, use of, on thermometers 45

Keys for shelter locks 4

"Khamsin " Q8

Legs or support for instrument shelter 7

Location of shelters 6

Location of station, change in 49

Locks for shelters 4

"Low" 76

Lightning 63, 64

Map of earthquake districts 79, 80, 81

Marks, graduation, renewal of, on thermometers 45

Maximum thermometer 9

care in reading 11

description of 9

mounting 22, 24

new supports for 23, 26

wooden supports for 22

reading of 27

" retreaters" 10

setting of 25, 51

temperature 47

reading of 50

INDEX. 35

Paragraph.
Mean temperature 48

determining of, from plus and minus 53

Measuring rainfall, units of 36

Mercury in maximum thermometer 9

Meteorological record 49

Meteorological terms 68-76

Minimum thermometer 12

alcohol column of 12

detached 13,14,15,31

hanging up 21

index of 12

sticking 13

mounting 22, 28

reuniting columns of 16, 17, 18, 19

reading of 30

setting of 21, 29, 51

temperature of 47

reading 50

testing 21

Minus and plus temperature signs 53

mean of 53

Mistakes made in record 49

Mock suns 62

Mounting thermometers 22, 24, 28

Nails, objection to use of, in packing 44

Name of station, change in 49

Newspaper clippings of earthquakes 82

* ' Norttier " 68, 70

Overflow of rain gage 34

Observations desired 47

of earthquakes 81, 82

time of making 48

Packing thermometers 44

" Pampero " 68

" Parhelia or Paraselenae " 62

Phenomena of climate 66

miscellaneous 67

Pigment, black, for thermometers 45

Plus and minus temperature signs 53

mean of 53

Post-oflSce address 49

Precipitation. {See Rain and snow.)

Processes of reuniting broken alcohol columns 16, 17, 18, 19

Quicksilver {see Mercury) 9

Rainj^U, absence of, recorded 49, 59

catch of 33

measuring of 34, 36, 37, 38, 39

overflow of 34

record of 55

units of measurements 36

Rain gage, catch of 33

description of 34

distance from shelter 3

exposure of 32

36 INDEX.

Paragraph.

Rain gage, size of 34

Reading maximum thermometer 11, 27

minimum thennometer 30

thennometers, use of plus and minus signs 53

discrepancies in 52

Receiver of rain gage , 34

Record of meteorological observations 47

Reports, preparation of 49

"Retreaters" 10

Roof exposure of rain gage 32

Sand storm 68

Screws, use of, in packing. 44

Seismology (see Earthquakes) 77-82

^'Setting" maximum thermometer 25, 51

minimum thermometer 21, 29, 51

thermometers, test of correctness 52

Shelter, instrument 3

exposure of 6

height above ground 7

installation of 7

legs or support of 7

locking of 54

locks for 4

'^Simoom'' 68

Smoke 67

Snowfall, measuring of 40, 41, 42, 43, 56, 57, 58, 59

record of 56

units of measurement 56

Snow gage 34

Solar corona 61

Squalls 70

Station, location of, change in 49

name of, change in 49

Stationery, for making records 49

Stick, measuring, for rainfall 36

Supports, box, for rain gage 35

maximum and minimum thermometers 3, 26

shelter 7

Temperature of free air 1

erroneous, guarding against 11

maximum 47

reading of 27

mean 48

when plus and minus 53

minimum 47

reading of 30

Testing minimum thermometers for defects 21

Thermometers, exposure of 2

broken, returning of 46

maximum. (See Maximum thermometer.)
minimum. (See Minimum thermometer.)

nonregistering (exposed) 53

packing of 44

INDEX. 37

Paragraph.

Thermometers, setting of 21, 25, 29, 51

test of correctness 52

time of 51

shelter for 3

shipment of 44

Thunderstorms 47, 63

Time of maldng observations. 48

Tornadoes 47, 64, 70

* * Townsend " thermometer supports, mounting of 23

oiling of 26

**Trace" of rainfall 59

Tube, measuring, of rain gage 34

diameter of 34

"Typhoon" 69

Water, measuring of, in rain gage 36, 37, 38, 39

Weather, state of 47

Whirling (setting) maximum thermometer 25

Whirlwind 71

Wind, disturbing effect on rain gage 32

intensity of, in tornadoes 64

Zero temperature reading 53

U. S. DEPARTMENT OF AGRICULTURE

WEATHER BUREAU :: :: :: Washington, D. C.

Instructions for
Cooperative Observers

CIRCULARS B AND C, INSTRUMENT
DIVISION :: Eighth Edition (Revised 1935)

1 •id C. Vaiha B<

TbeimooteMr sheltei and raltt gage lor cooperative ot

W. B. No. 843

U. S. DEPARTMENT OF AGRICULTURE
WEATHER BUREAU

INSTRUCTIONS

FOR

COOPERATIVE OBSERVERS

CIRCULARS B AND C, INSTRUMENT DIVISION
EIGHTH EDITION (REVISED 1935)

UNITED STATES

GOVERNMENT PRINTING OFFICE

WASHINGTON: 1836

Fur anil! Iij the SuperluteodeDt ot Dnc^uropats. Wash log! on. D. C. -

UNITED SI MISO'" AMERICA

S?P

•»

TABLE OF CONTENTS

Introduction

Page
1

T. Instructions for the erection and care of instruments 2

The object of temperature readings and exposure of thermometers _. 2

General description of thermometers 5

Instructions for reuniting detached columns of alcohol 7

Instructions for mounting maximum and minimum thermometers 10

The rain gage 13

How to measure rainfall and snowfall 15

General instructions about instruments 17

II. To make and record observations 18

Temperature records 19

Precipitation records 20

Miscellaneous phenomena 21

Nomenclature 23

Form 1009, meteorological, sample monthly record 25, 26

III. Earthquakes and instructions for their noninstrumental observation. 27

Importance of earthquake data 27

Why the Weather Bureau should collect earthquake data 27

Request for cooperative observers 28

Instructions for the collection of earthquake data 28

LIST OF ILLUSTRATIONS

Circular B & C, Instrument Division

(Seventh edition)

Page

Thermometer shelter and rain gage for cooperative observers Frontispiece

Fig. 1 . Details of support for small instrument shelter 4

Fig. 2. Instrument shelter on support, showing angle anchors buried in

ground Opposite p. 5

Fig. 3. Showing first process of reuniting alcohol column in minimum

thermometer 8

Fig. 4. Showing second process of reuniting alcohol column in minimum

thermometer 8

Fig. 5. Showing third process for reuniting alcohol column in minimum

thermometer 9

Fig. 6. Setting maximum thermometer, board support 11

Fig. 7. Setting minimum thermometer, board support 11

Fig. 8. Townsend support, pawl disengaged, maximum rotating 11

Fig. 9. The maximum thermometer should be gently lowered to the read-
ing position 12

Fig. 10. Rain gage, showing details of 14

Fig. 11. Rain gage and box support 16

INSTRUCTIONS FOR COOPERATIVE OBSERVERS OF THE

WEATHER BUREAU

INTRODUCTION

To render these observations of the greatest value and to facilitate
their use in investigating questions relating to climate, a uniform
system for the exposure of the instruments and the recording of the
observations is in use.

The cooperative observer who each day faithfully records the read-
ings of liis instruments and notes the meteorological conditions pre-
vailing at his station is performing a valuable public service. The
publications in which his records appear are constantly consulted by
persons in practically every walk of life, seeking information regard-
ing cUmatic conditions from the most authoritative sources.

Cooperative observers receive no money compensation for their
services, but they regularly receive such of the publications of the
Weather Bureau as can be furnished free of cost.

As the value of a meteorologoical record increases with the length
of the period covered, continuity of record is of the utmost impor-
tance, and it is urgently recommended that those who undertake to

I INSTRUCTIONS FOR COOPERATIVE OBSERVERS

conduct observations endeavor to provide, as far as practicable, for
an uninterrupted series. A member of the observer's family, or other
competent person, should be fully instructed in the matter of taking
and recording observations, so that no break in the record will result
from the temporary absence of the observer or from his inability
from any cause to make the necessary observations.

For the purpose of securing the observations necessary to meet the
requirements of those entitled to such information, the Chief of the
Weather Bureau is authorized by law to loan instruments to persons
willing to take the observations, on certain conditions. These con-
ditions, in the main, are the safe-keeping of the instruments, their
return to the Weather Bureau if for any reason the station is discon-
tinued, and the furnishing of copies of the observations to the section
director of the climatological service of the Weather Bureau for the
State where located, free of expense to the Government.

Cooperative observers are usually furnished with maximum and
minimum thermometers, instrument shelters, and rain gages, but not
with barometers, wind vanes, or anemometers; nor will instruments
be supplied when the proposed station is considered too near others
already established.

Cooperative observers who fail to comply with the conditions upon
which Weather Bureau instruments have been issued will be called
upon by the section director to return them.

Blank forms and franked envelopes are furnished free of expense
to the observers for transmitting reports to the section centers.

Observers willing to furnish the local press with meteorological
data for pubhcation will be supplied with suitable postal-card forms,
properly addressed, upon application to the section director.

The cooperative observer is requested to fill up and forward to the
section center, as soon as the equipment is installed, a copy of Form
No. 4029 Mis. (Description of cooperative observer's station and
instruments), and when any change is made in the location of instru-
ments to promptly notify the official in charge of the section center.

All correspondence relative to the work of a cooperative station
and requests for instruments, supplies, etc., should be addressed to
the official in charge of the section center, who will furnish such infor-
mation as may be required and act promptly upon the requests.

I. INSTRUCTIONS FOR THE ERECTION AND CARE OF INSTRUMENTS

THE OBJECT OF TEMPERATURE READINGS AND THE EXPOSURE OF

THERMOMETERS

1. Temperature of the air. — The use of thermometers in meteoro-
logical observation is for the purpose of obtaining the temperature of
the free air. It is very important to always bear in mind that the
actual temperature of the free air is the object of measurements.

INSTKXJCTIONS FOR COOPERATIVE OBSERVERS 3

The air near the surface of the earth is nearly always in motion
more or less, and when not confined in a comparatively closed space
the several portions thoroughly intermingle with each other and
have nearly or quite the same temperature. When any portion of
the air is confined, however, so that it can not intermingle freely
with the general air masses, its temperature will be influenced to a
marked extent by the local surroundings and will not be a free-air
temperature.

2. These ideas show us at once that if we mean to make observa-
tions of the real air temperatures our thermometers must, if possible,
be placed in a perfectly open space where the circulation of the air
is entirely unobstructed. It will not do, however, to place the ther-
miometers simply in the open air, exposed freely to the sky and the
direct rays of the sun. The sunshine would cause the thermometer
to register too high, and" even if not exposed directly to the sun it
could not be depended upon to indicate the true air temperature
either day or night.

3. Thermometer shelter. — To overcome these difficulties it is neces-
sary to employ a thermometer shelter. This is nothing more than a
white box with louvred sides made in such a way that the air can
move through it with the greatest possible freedom. This is an
essential condition in thermometer exposure. The object of the box
or shelter is simply to screen off the direct and reflected sunshine and
the radiation to and from the sky and to keep the thermometers dry.

To obtain the true air temperature, therefore, place all thermome-
ters in a suitable shelter exposed in the open, or on a house top,
where the circulation of the air is as free as possible. When the
shelter can not be placed in a field or open space or on the top of a
house, it may be placed on the north side of some buildings. It
should not be placed on a building liable to be shaken, as jarring
tends to displace the index of the minimum thermometer and make
readings of that instrument erroneous.

The standard shelter for cooperative work is shown with its support
in the frontispiece, together with the maximum and minimum ther-
mometers properly mounted on the Townsend support,which are
illustrated in greater detail in figures 8 and 9. The picture shows also
the rain gage, but in order to bring this into the picture it was placed
nearer the shelter than it should be in actual use. The rain gage
should be at least 15 or 20 feet from the shelter.

4. Installation oj shelter and support. — Shelters sent to observers
from the central office are assembled complete ready to be set up,
and each shelter is usually accompanied by a support made up accord-
ing to the details given in figure 1 . The assembled support with the
shelter mounted thereon is plainly shown in the frontispiece and in
figure 2. It is frequently better to arrange for a support to be con-

4 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

structed locally so that four substantial posts of material, known to
last well in the ground and long enough to provide a good anchorage,
may be employed.

The instrument shelter support comes shipped knocked down, and
must be assembled as follows:

Make up each end section first as follows: Lay two legs on a floor
or other flat surface. There will be found on each leg a pencil mark
near the top and another near the middle on two adjacent sides of
the legs. Place the legs so that these marks are on top and on the
outside. A wide short girt, having two countersunk screw holes,
should be nailed to the two legs, the lower edge to the pencil line near
the top oj the legs. It will be noticed that this girt extends 1 inch
beyond the top of the legs. This is to enable it when the support is
completed to clasp the shelter and be screwed thereto. The short
lower girt will be nailed to the legs with its upper edge on the lower

Front or rear section. End section.

Fig. 1. — Details of support for small instrument shelter.

pencil mark. The ends of both girts should be flush with the outside
of the legs. A short brace should then be nailed in position with
the lower end to right and with the beveled ends flush with the out-
side faces of the legs. It is suggested that the parts be laid down
before nailing, and that only one nail be driven at each joint until
after the brace is in position.

The two long upper girts can then be nailed on, their ends coining
out flush with the outside edges of the wide upper girts, and their
lower edges to the pencil lines. In a similar maimer nail the two
long lower girts, their upper edges to the pencil lines and their ends
flush with the outside faces of the lower girts of the end sections.
Now nail the two long braces in position, left end lowermost, and if
the end sections were braced properly it will be found that the ends of
the long braces will meet and cover the ends of the short braces.

Ciicului B iiid C Wuihct Bi

FiouEE 2.~lii3mitneat shelter on support, sbowlng anile ancbora bi

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 5

The eight crosspieces from the crate in which the instrument shelter
support is shipped may be used to anchor it to the ground, but it is
much better to provide suitable anchor posts locally of material
known to last well in the ground.

5. Locks jor instrument shelters. — For several years past all shelters
issued to stations from the central office have been furnished with
the same kind of lock and key (known as the- no. 39.). This is the
standard lock, and new keys can always be procured promptly on
application to the section center, where a small stock will be kept.

6. Old-style locks. — Prior to the adoption of the above no. 39 lock
a so-called **No. 9'' lock was used for 2 or 3 years, and extra keys for
this lock can be obtained from the Central Office. Sections having
trouble with locks not of either of the above patterns should make
appUcation for the standard lock (no. 39) and key (no. 6).

7. Location or exposure oj shelter. — The shelter should be set up,
whenever possible, over grass-covered ground and in an open, clear
space easily accessible to the observer, and about 4 feet above the
ground. Where such a location is not obtainable, however, the
shelter may be placed on the roof, or secured to the north wall of a
building by means of suitable screws through the back of the shelter,
which should be held 2 or 3 inches away from the wall by previously
spiking thick strips of wood thereon.

GENERAL DESCRIPTION OF THERMOMETEPS

8. Before the observer attempts to set up the thermometers, let
him first examine them and compare them with the description and
famiUarize himself with all the peculiarities of each, so that he may
understand which is the maximum and which is the minimum.

9. Maximum thermometer. — The maximum thermometer is always
filled with mercury, sometimes called quicksilver.

The most distinctive peculiarity of the maximum thermometer,
however, is not so easily seen. If the observer will hold the ther-
mometer vertically with the bulb down, he will notice that the mer-
curial column does not extend entirely into the bulb. A close exami-
nation of the thermometer at the point just above the bulb where the
mercurial column stops will show that the glass tube seems to have
been almost closed at that point. This is just what has been done,
and the passageway for the mercury is so fine at that point that the
mercury will go through only with some difficulty. The observer
should next hold his warm fingers around the bulb. The mercury in
the bulb, expanding as it becomes warm, will then be forced to pass
the constricted portion of the tube, flowing through in little spurts.
When the fingers are removed from the bulb the mercury below the
constriction, contracting as it cools, withdraws toward the bulb, but
none of the mercury above the constriction goes back, and the length

119719—35 2

6 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

of the column remains the same as it was when the bulb was warmest.
In this way the maximum temperature is registered.

If the thermometer is held in a horizontal position and then alter-
nately tilted — first with bulb higher than stem, then with bulb lower
than stem — it will be noticed that the thread of mercury may be
made to flow to either end of the tube as desired.

10. Retreaters. — Experience has shown that in spite of every care
in the inspection and testing of maximum thermometers they will,
if exposed vertically, sometimes fail to record the maximum tempera-
ture; that is to say, the constriction in the bore of the tube is not so
fine as required, and when the temperature falls after reaching the
maximum point the mercury in the column of the thermometer
withdraws into the bulb and the record of the maximum temperature
is lost. Such thermometers are sometimes said *Ho retreat'', and are
called ''retreaters."

A good maximum thermometer may be made a retreater by a too
violent throwdown of the mercury, as explained in paragraph 25.

1 1 . Since it is known that a maximum thermometer may become a
retreater without that fact being noticed, the safest procedure is to
mount it with the bulb a little higher than the stem, as shown in
figure 7. In this position the column of mercury is not under pres-
sure, and when the thermometer is lowered gently to reading position
it will rarely fail to record the highest temperature reached.

When it is desired to make a reading, the thermometer must be
slowly and carefully lowered to a position in which the mercury rests
on the constriction. This reading position, or angle, is not the same
for all maximum thermometers, but rather should be determined by
the observer watcliing the manner in which the mercurv flows in the
tube at different angles of elevation. Greater care must be used with
high temperatures because of the greater weight of the long column
of mercury.

After reading, the thermometer should be set by whirling as
described in paragraph 25.

12. Minimum thermometer, — This thermometer, as used by the
Weather Bureau, is always fiUed with alcohol, and is therefore at
once distinguished from a mercurial thermometer. Besides the alco-
hol there is inside the thermometer also a little black object having a
rounded head on each end. This object is called the index and is
the prime characteristic by which this kind of minimum thermometer
is distinguished from all other thermometers.

13. Generally the index will slide freely up and down the thermom-
eter tube when one end is raised or lowered. Sometimes, however,
and especially after the thermometer has been shipped, the alcohol
in the tube becomes broken up into short, detached columns and the
index is frequently caught and held.

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 7

14. Of course the thermometer cannot be used until this is reme-
died, which in some cases proves to be a difficult operation. Observ-
ers are requested to use special care in learning and following the
instructions given below and to notice carefully the several effects
so that they may judge for themselves as to what need be done to
unite detached columns and avoid the danger of breaking the
instrument.

The fact that vapor of alcohol condenses in the upper end of a
minimum thermometer is well known to those who handle a con-
siderable number of such thermometers. Manufacturers seal off
such thermometers under considerable air pressure in order to lessen
the probability of separation; but it will be apparent upon reflection
that when a marked fall of air temperature occurs, conditions favor-
able for condensation of the vapor of the alcohol coincide with lessen-
ing of internal pressure, due to increased space above the column.

Under such circumstances a good minimum thermometer is likely
to be misjudged as defective, when all that is needed to correct the
condition is to reunite the column, then hang it in a vertical position
for an hour or more so that the alcohol adhering to the walls may
drain down. The test for the success of the effort is simple — merely
to set the thermometer, immersed up to the reading point in melting,
shaved, pure ice, or snow. Within an hour or so it should read very
close to 32''.

15. The many different ways in which the alcohol column becomes
separated make it impossible to unit it by any single method, different
methods being required not only for different conditions but also for
different thermometers.

Frequently there are only a few short, detached portions near the
top, and the index sUdes freely along the lower portion of the tube
and drops into the bulb. Again, the detached columns are found all
along the tube, and the index is caught and held at some point above
the main column. In such a case it is advisable to first bring the
index into the bulb as follows:

16. First process. — Hold the thermometer lightly between the
thumb and fingers and strike the lower end of the metallic scale
against the top of a table or other firm object, as shown in figure 3,
first, however, interposing 1 or 2 thicknesses of cloth or several folds
of paper, so as not to produce too severe a shock upon the thermom-
eter. The taps of the thermometer should be Ughtly made at first
and the index examined to see if it has not moved along the tube
even a little distance, as can be told by noticing the exact position
of the index in reference to the graduations on the tube. If several
taps fail to move the index, increase the force of the taps a little at a
time until the index starts, after which repeat the operation until the
index gets within the continuous (^.olumn. Here it will fall of its

» INSTRUCTIONS FOR COOPERATIVE OBSERVERS

own weight into the bulb. Generally this will be all that is necessary
t,n n]nc.p flip inripv in tlic biilb. Sometimes the
ilso have been partly or
column is still broken in
places, the observer
' should try a few more
taps, and examine quick-
ly in a very careful man-
ner. Small portions of
the alcohol will general-
ly be seen slowly mov-
ing along the sidei^ of the
tube toward the main
column, and a continu-
ation of the taps will
unite the columns. In
some cases 15 or 20
;es may be required to
completely unite broken col-
umns. If, however, the index
cannot be made to move with
quite hard taps, or the columns
cannot be united , it is advisable
to try some of the methods des-
cribed next, being careful always to avoid carrying any process so far
as to endanger breaking the
thermometer.

17. Second process. — This
method will not loosen the index,
but may unite the detached col-
umns. Grasp the thermometer
securely a little below the mid-
dle, with the bulb end down, and
strike the edge of the metal back
opposite the broken column
sharply against the fleshy por-
tion of the palm of the other
hand, or, if necessary, against a
small block of wood held in the
hand. (See fig. 4.) A continued
jarring in this way often causes
the alcohol to run down, though p^^ ^

in many cases a large number of

taps are necessary. Observers should therefore not give up if the
column does not unite at once, but should watch very closely for the

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 9

■novements of small portions of alcohol along the sides of the tube.
Here, again, care must be exercised not to strike too hard and to hold
the thermometer by the metal back in such a manner as not to
squeeze or press against the stem of the thermometer itself. When
the bore of the thermometer is large, the above process is almost sure
to unite the column. Good results are also obtained with thermom-
eters of fine bore, though the latter, even in skilled hands, often
require a half hour or more of time if the column is badly detached.

18. Third process. — This method can also be used in place of those
above and is sometimes effective in forcing the index into the bulb.
Grasp the thermometer a little above the middle, clasping the fingers
and hand firmly against the edges of

the metallic back, but not so as to
bring any pressure upon the glass
tube, which should be turned toward
you and with the bulb uppermost, as
shown in figure 5. Witli the thermom-
eter in this position and about as
high as the liead and the arm free
from the body, quickly lower the arm
and hand a foot or more, turning the
wrist at the same time, so that the
bulb of the thermometer describes a
somewhat circular path downward
through the air, stopping the motion
with a sudden jerk just as the ther-
mometer is vertical. If the thermom-
eter isgrasped properly, a very violent
motion can be given in this way
without danger. It will sometimes
be necessary to repeat the operation
a great number of times to entirely
unite the detached columns,

19. Fourth process. — A modification ^"'^^^

of the swinging process just described consists in whirling the ther-
mometer rapidly on a short string. For this purpose a stout string
is passed through the hole in the top of the metal back of the ther-
mometer. This is left double and firmly grasped at a distance of 6 or
8 inches from the thermometer, wliich may then be given a very rapid
whirling motion. Considerable care and practice are required to whirl
the thermometer rapidly and stop it safely. This method will, how-
ever, often bring down the index and unite detached columns.

"20. If observers are unsuccessful after carefully following the above
instructions, the matter should be reported to the section center,
giving full particulars as to what has been done.

10 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

21 . Testing minimum thermometer. — Some one or more of these proc-
esses should in nearly all instances be suflBcient to unite any detached
column, and when all the bubbles have been removed the observer
can then see how the instrument works. Hold the thermometer
vertically and warm up the bulb by holding it in the hand ; then turn
the instrument upside down. Watch the index as it glides along the
tube; when it strikes the top of the column it will at once stop. This
operation of bringing the index to the top of the column is called
** setting*' the thermometer.

Next hold the thermometer horizontally. As the bulb cools off
the index will be dragged backward toward the bulb, but alw^ays
remains at the end of the column of alcohol. It is a good plan to
hasten the cooling by placing a Uttle wet cloth or piece of ice against
the bulb. When you have watched the index go down with the
column, warm the bulb again with the hand. The column will go up
immediately, but the alcohol will flow around the index and leave
it at the lowest point; that is, the index remains so that its top end
is at the lowest point reached by the alcohol column, and the mini-
mum temperature is indicated in this way. The thermometer must
be held horizontally throughout these operations.

When the thermometer is not in use for observation, it is a good
plan to hang it up, as bubbles are less likely to form in the tube in
this position.

The thermometer should also be maintained in a vertical position
for several hours after a broken column has been united to permit
any alcohol clinging to the sides of the bore to drain down.

INSTRUCTIONS FOR MOUNTING MAXIMUM AND MINIMUM THERMOMETERS

22. The style of wooden support shown in figures 6 and 7, while
in use at many of the oldest stations is being replaced by the so-called
'^Townsend support'^ shown in figures 8 and 9. The use of the wooden
support will be suflBciently understood, it is believed, from the figures
without detailed instructions.

23. The Tovmsend thermometer support. — This support, with ther-
mometers attached, shown in figures 8 and 9, should be firmly screwed
to the cross board of the instrument shelter, approximately in the
middle, and with the legend **U. S. W. B. '' right side up.

24. Maximum thermometer. — Mount the maximum thermometer
on the carrier on the long projection stud, and clamp it just below
the upper strap, and with the bulb at the left, so that it over balances
and tends to hang bulb end down.

25. To whirl and set the maximum thermometer. — Release the pawl
fixed near the base of the maximum pin. This unlocks the carrier.
Place the finger, or pencil, at one side of the thermometer scale and
impart to it a rapid rotation, as suggested by the dotted Une and

INSTRUCTIONS FOR COOPERATIVE OBSERVERS

arrow in figure 8. Allow the thermometer to whirl until it comes
to rest itself. Do not try to stop it while whiiling. Note carefully

whether or not the space between the bulb and constriction is filled
with mercury. Repeat the whirling, if necessary, until the column is
whirled down as far as it can go.

12 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

The space in the bore of the tube not occupied by the mercury is a
vacuum. Hence, the mercury should rest upon the constriction when
whirling is started. Otherwise its violent throwdown may fracture
the glass constriction. When such internal fracture has occurred it
will be apparent as an irridescent patch in the neighborhood of the
constriction when the thermometer is examined by reflected light.

26. The revolving carrier for the maximum thermometer must be
oiled occasionally through the hole in the side provided for the pur-
pose so that the carrier will revolve easily. A thin, nongumming
oil should be used.

Fra. 0.~The maiiniiim tbennometet abould be gsotly lowerPd to Ibe readiDg poaitioo.

Attention is invited to the fact that maximum thermometers
purchased by the bureau under contracts dating from July 1, 1913,
are not fitted with brass hubs for mounting and whirling the same,
as used with the so-called "old-style" supports. Therefore, where a
cooperative or other station has the old brass supports for maximum
and minimum thermometers in use, and the new pattern maximum
thermometer is supplied, it is necessary, also, to replace the supports
with the Townsend pattern, obtainable on stores requisition in the
usual manner,

27, To read the maximum thermometer . — First carefully dis-
engage the pin or pawl that holds the maximum thermometer in a
nearly horizontal position, then slowly lower it, bulb end down, until
the mercury rests on the constriction. The thermometer must not
be lowered suddenly, especially in warm weather, as the weight of
the long column of mercury is likely to force some portion through

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 13

the constriction and cause an erroneous reading. The maximum
temperature is the scale reading at the top of the column of mercury.

28. Mounting minimum thermometer, — The minimum thermom-
eter must be mounted upon the carrier on the short projecting stud.
Clamp the thermometer in the carrier at about the middle point,
with the bulb end to the left.

29. To set the minimum thermometer. — Turn the carrier and ther-
mometer to a vertical position, bulb uppermost, and allow the index
to fall to the end of the column. After setting do not fail to turn the
minimum thermometer back to its horizontal position as shown in
figures 8 and 9.

30. To read the minimum thermometer. — The minimum thermom-
eter must always be read while it is still in its horizontal position as
left after setting at the previous observation. To avoid possible dis-
placement by vibrations, the minimum thermometer must be read
before whirling and setting the maximum thermometer. The read-
ing is obtained by noting the number of degrees on the scale opposite
the end of the index farthest from the bulb. A reading taken at the
end of the spirit column will give the current temperature.

31. If at any time the column is found to be broken and bubbles
are observed in the tube the instrument should be taken off the
supports and an effort made to unite the column by some of the
methods already described.

THE RAIN QAGE

32. The exposure of the rain gage is a very important matter.
The most serious disturbing effect in collecting rainfall is the wind.
In blowing against the gage the eddies of wind formed about the
mouth tend to carry the rain away, so that frequently too little is
caught in the gage.

Observers will therefore take particular care in selecting a place
for the location of the gage, as the value of the records is sometimes
greatly impaired by improper exposure. It is scarcely necessary to
say that every precaution should be taken to protect gages from the
interference of animals and unauthorized persons. Select, if possi-
ble, a position in some open lot, unobstructed by large trees, buildings,
or fences. Low bushes and fences, or walls that break the force of
the wind in the vicinity of the gage, are, however, beneficial, if at a
distance at least twice as great as the height of the object. Such
surroimdings, in general, afford the best exposure. Gages should be
exposed upon roofs of buildings only when ground exposures are
impracticable, and then the roof should be flat, or nearly so, and the
middle portion should be selected to get the best results.

119719 — 35 3

INSTRUCTIONS FOR COOPERATIVE OBSERVERS

33. Kain gages in slightly different positions, if badly exposed,
catch very different amounts of rainfall. Within a few^ yards of
each other two gages may show a difference of 20 percent in the
fall in a heavy rainstorm. The stronger the wind the greater the
difference is apt to be. In a high location eddies of wind produced
by walls of buildings divert rain that would otherwise fall in the
gage. A gnge near the edge of the roof, on the windward side of a
building, shows less rainfall than one in the center of the roof. The
vertical ascending current along the side of the wall extends slightly
above the level of the roof, and part of the rain is carried away
from the gage. In the center of a lai^e, flat roof, at least 60 feet

FiQ. 10.— Rain gage.

square, the rainfall collected by a gage does not differ materially
from that collected at the level of the ground.

34. Description oj rain gage. — The rain gage consists of the follow-
ing parts:

The receiver A;

The overflow attachment B;

The measuring tube C

The top cylindrical portion of the receiver, marked a in figure
10, is exactly 8 inches in diameter, inside, and is provided with a
funnel-shaped bottom, which conducts any precipitation caught in
the receiver into the tall cylindrical measuring tube, C, the total height

INSTKXJCTIONS FOR COOPERATIVE OBSERVERS 15

of which, inside, is exactly 20 inches. The diameter of this tube is

much smaller than the large receiving tube, a, being only 2.53 inches.

In consequence of this a small amount of rain falling into the receiver

and flowing into C fills the latter to a depth greater than the actual

rainfall in proportion as the area of the receiver is greater than the

area of the measuring tube. In the standard gages of the Weather

Bureau the depth of the rainfall, in accordance with this principle, is

magnified just 10 times. The receiver, A^ has a sleeve, rf, figure 10,

which sUps over the tube, C, and very effectually prevents any loss of

rainfall. Again, when the rainfall is very heavy, the tube, C, may

overflow. In this case, to prevent loss, a little opening, shown at

c, figure 10, is made in the sleeve, d, just on a level with the top of

the tube, C The excess of rainfall escapes through this opening, and

is retained in the large overflow attachment, J5, and can be measured

afterwards, as will be described later. The opening e is omitted in

the latest forms of gages, as the water easily flows between the sleeve

and the tube C, which fit each other loosely. The inside diameter

of the overflow attachment is just 8 inches, and this portion of the

instrument can be used as a snow gage, as will be explained hereafter.

35. Rain-gage support, — The box in which the gage is shipped to
the observer is expressly designed as a stand for the instrument, and
should be opened at the head, which is fastened by screws. Set the
box as nearly vertical as possible at the place selected for exposure and
secure it in this position by driving down four stakes alongside, in the
manner indicated in figiu'e 1 1 . Care must be taken to have the gage
held in a truly vertical position. Slip in the head and lower it to the
level of the screw holes in the sides of the box about 10 inches from
the bottom, where the head will be securely fastened with the screws
taken out in opening the box. The gage can now be placed inside,
and appears as shown in figure 11.

HOW TO MEASURE RAINFALL AND SNOWFALL

36. Rainfall, — The measuring stick of the rain gage is graduated
into inches and tenths. Remembering that the actual depth of the
rainfall is magnified 10 times, as explained above, it is plain that if
we find the water 10 inches deep in the measuring tube, then the actual
rainfall must have been only 1 inch deep, or if the water in the tube
is only one-tenth inch (or written as a decimal, 0.1 inch) deep, then
the rainfall must have been only one one-hundredth inch (or written
as a decimal, 0.01 inch).

16 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

niimboring of this division, as stamped on the stick, ffives, as has just
heen explained, the actual depth of rainfall, and in making out records
and reports observers should always use the decimal expressions.

38. After measuring and recording in this way the precipitation
found in the gage the top should be removed, the measuring tube
emptied and drained, and the gage put in position again. Observers
should be careful after emptying the gage to replace the measuring
tube so that the bottom stands within the ring in the middle of the
bottom of the overflow, and in putting on the receiver that it passes
over the measuring tube and rests squarely down upon the overflow,
39. When the amount of rain that has
fallen more than fills the measuring tube,
some care is required to determine the
total rainfall. First carefully remove the
receiver so as not to spill any of the water
in the measuring tube, which should be
exactly full. If some water has been
slopped out and the measuring tube is
not exactly full, the amount of water re-
maining must be accurately measured
with the stick, as already described. The
tube is then lifted out slowly and care-
fully, so as not to spill any of the water
into the overflow, emptied, and allowed
to drain a moment or so. The water
remaining in the overflow is now poured
into the measuring tube, care being taken
not to lose any, and measured in the usual
way. Suppose we find this to be 0.47
inch rainfall; then, remembering that the
measuring tube is just 20 inches high,
the total rainfall will be 2 inclie3-l-0.47
lo.ii.— aagagenn support. inch=2.47 inches. Or, in casc some Water
was spilled from the measuring tube, the 0.47 inch should be simply
added to the first measured amount to give the total rainfall.

40. Snowfall. — During the winter season, especially in those cli-
mates where the precipitation is nearly all in the form of snow, the
overflow attachment only of the rain g^e should be exposed in the
support as a snow gage. Remove the receiver and measuring tube to
the house, as these parts cannot be used for measuring snow, and
even if rain should occur it is very apt to be frozen while in the
measuring tube, generally bursting it and rendering it worthless or
highly inaccurate.

41. First method. — The snowfall collected in the overflow attach-
ment is measured after placing the vessel in a warm room until the

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 17

snow is melted. The water is then carefully poured into the meas-
uring tube and measured just as though it were rainfall.

42. Second method, — The first method is objectionable, because it
often requires considerable time, and is Uable to be inaccurate, owing
to the loss of the snow or water by evaporation. The following plan
is noLUch better, unless clumsily conducted so as to spill and waste
the water: Take the overflow into the room and pour into it care-
fully one measuring tube full to the brim with water, preferably warm
water. This, in general, will mostly melt, or at least reduce to a
very fluid slush, a considerable snowfall. The measuring tube should
be again carefully filled to the brim from the melted contents of
the overflow and emptied; whereupon the remaining water in the
overflow should be carefully measured in the measuring tube, thus
giving quickly and easily the depth of melted snow.

43. The amount of snow collected in the overflow of the rain gage
is likely to be greatly deficient when the wind blows during the
snowfall. In such cases it will be much better if the observer will
discard the snowfall in the overflow, empty it out and cut out a sec-
tion of the snow in an open place where the depth truly represents the
precipitation. This section is to be taken by plunging the empty
overflow, mouth downward, in the snow so as to cut out a cylindrical
portion the size of the overflow and the depth of the snow. By the
use of a thin board or other means it will not be difl5cult to gather
up the complete section of snow inside the overflow, after which it
should be reduced to slush and measured as already explained.

GENERAL INSTRUCTIONS ABOUT INSTRUMENTS

44. Shipment of thermometers, — The boxes and packing material
received with thermometers should be carefully preserved for use in
returning instruments.

45. Use of ivory black. — When, from action of the weather and
long exposure, the graduation marks, figures, or lettering on the glass
tube, enamel scale, or metallic back of a thermometer are obliterated
or illegible, they can easily be renewed by the application of a small
quantity of artists' black pigment (ivory black). The best method
of applying the substance is to put a drop on a small stick, such as
a match, and rub it across the marks or lettering until the spaces are
thoroughly filled. The superfluous pigment should then be wiped
off with a piece of tissue or blotting paper in such manner as not
to draw the pigment from the lines.

it-V \ i •4.tl1,-

18 INSTKUCTIONS FOR COOPERATIVE OBSERVERS

46. Action to take when instruments are broken. — When from any
cause instruments are broken they should be promptly returned,
with an explanation, to the section center.

Ordinary precautions are required in the use of instruments, and
observers are requested to use every reasonable care to avoid acci-
dents, breakage, and loss.

n. TO MAKE AND RECORD OBSERVATIONS

47. Observations desired. — It is requested that cooperative observers
make and record, daily, observations of the maximum and minimum
temperatures; precipitation (rainfall or snowfall); the state of the
weather (that is, the general character of the day from sunrise to
sunset) ; and such other miscellaneous phenomena as fog, frost, coro-
nas, thunderstorms, hail, sleet, tornadoes, and auroras.

Form no. 1009, furnished by the section centers, is arranged to facili-
tate recording the data desired by the Weather Bureau.

48. Time of making observations. — ^But one observation in each 24
hours is necessary on the part of cooperative observers, since the aver-
age of the readings of the maximum and minimum thermometers gives
an approximately correct mean temperature for the day.

Uniformity as to time of taking observations is desired. A definite
hour should be determined upon and the observations made each day
as near that hour as possible. About sunset is recommended as the
most satisfactory time for making the record, as the thermometers
will then, except under unusual conditions, register both maximum
and minimum temperatures for the day. The time at which obser-
vations are taken should invariably be noted on form no. 1009.

49. Form no. 1009 , meteorological monthly record.-^At the end of this
pamphlet will be foimd a copy of the form used by cooperative ob-
servers for recording observations, with data properly filled in, to
show how observations should be recorded.

It is particularly important, in the interest of accuracy, that the
observations be recorded as soon as made, and that the entries be
made day by day as observed. Even if no rain has fallen, the observer
should bear in mind that his oflBcial record of that fact is as impor-
tant as the record of rainfall.

Special care should be exercised in the preparation of reports; pen-
cils should be kept sharp, and good carbon paper used to insure sat-
isfactory duplicate copies. Three copies of the report should be
made, one to be retained by the observer and two to be sent to the
section center on the first of each month. To make 3 copies of
the record requires 2 carbon sheets; these should be placed between
the forms, carbon side facing the form on which the record is to be
made, and an ordinary pencil — one not too soft — used in writing.
If a mistake occurs in recording, attempt should not be made to write

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 19

over the figures; draw a line through the incorrect entry and make
new figures either to the right or left, or on the margin of the form.

When the carbon paper no longer makes clear duplicates, ask for
a new supply. It is the wish of the Chief of the Weather Bureau to
keep cooperative observers well supplied with all material pertaining
to their oflBcial duties, and they are requested to make timely requisi-
tions therefor on their respective section centers.

When the name of the station and its post office are not the same,
both should always be entered on form no. 1009, the name of the
station at the top of the form, and any change in location or name
of the station should be explained by note.

TEMPERATURE RECORDS

50. The readings of the maximum and minimum thermometers
should be made as explained in paragraphs 27 and 30 and recorded in
the appropriate columns of form no. 1009.

In recording maximum and minimum temperature the following
should be borne in mind. The maximum temperature of any day
cannot be lower than any of the following readings: (1) The minimum
of the previous day; (2) the minimum of the same day; (3) the mini-
mum of the following day; (4) the set maximum of the preceding day;
(5) the set maximum of the same day.

The minimum temperature of any day cannot be higher than (6) the
maximum of the preceding day, (7) the maximum of same day, (8) the
maximum of the following day, (9) the set maximum of the day before,
(10) the set maximum of the same day.

The maximum should be whirled and set first, and the minimum
next. In no case should the thermometer be set, except once each
day, just after making the observation.

52. Test. — After setting the thermometers the readings of the toj)
end of the index of the minimum thermometer and the top of the
mercurial column of the maximum should give one and the same
temperature generally within a fraction of a degree. If the difference
is a degree or more, and it cannot be corrected by resetting, it is pos-
sibly due to bubbles in the minimum thermometer or slight displace-
ments of the alcohol. Persistent discrepancies of this sort should be
reported to the section center, and observers are requested to have
this test in mind and apply it frequently in order to detect this source
of inaccurate records.

53. Plus and minus signs. — Temperatures below zero are written
with the minus sign prefixed, thus: —1, —2, —4, etc., all indicate that

20 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

the temperature is below zero. If the temperature is exactly zero it
should be recorded 0. Temperatures above zero are recorded simply
2, 45, etc., as the case may be, it being understood by the absence of
any sign that it is (+), or above zero.

In determining means when there are minus (below zero) tempera-
tures, the sum of the minus readings must be deducted from the sum
of the plus readings and the remainder divided by the number of
days in the month, unless one or more days' records are missing, when,
of course, those missing days must be deducted from the divisor.

If the sum of the minus readings is greater than the sum of the plus
readings, the latter should be subtracted from the former and the re-
mainder divided, as above. The resulting mean is a minus temperature.

54. Shelter locked. — The shelter should be carefuUv locked after
taking each observation in order to prevent unauthorized persons from
interfering with the instruments.

PRECIPITATION RECORDS

55. Rainfall. — Measurements of rainfall should be made at the
time of regular observations, and the gage should be emptied of all
the water it may contain as soon as it has been measured and the
parts replaced in readiness for the collection of the next rainfall.
The amount of rainfall will be determined as explained in paragraphs
37, 38, and 39.

56. Snowfall. — Snowfall is preferably measured as depth of water
rather than by the thickness of layer it forms on the ground. When
it cannot be measured accurately by melting, it is customary to take
one-tenth the measured depth of the snowfall on a level, open place
as the water equivalent of the snowfall. The relation between the
depth of snow and depth of melted snow is very different in different
cases, depending on the wetness of the snow. The equivalent depth
of water in some cases is as great as one-seventh of the depth of snow,
and in others only one thirty-fourth. It is always best to reduce
snow to a liquid condition for measurement, and the simplest way to
do this is to add to it a known volume of water sufficient to reduce it
to a state of slush, as explained in paragraph 42. For each entry in
the column headed ^* Snowfall" there must be an entry in the column
*' Amount." For rainfall but one entry is made; for snowfall, two,
one of which is the depth of the snow, the other the depth of the
water obtaining by melting the snow.

57. In the winter season the overflow only of the gage should be
exposed, as stated in paragraph 40, and the snow collected therein
between observations (or, better, a section of snow cut out as explained
in paragraph (43) should be reduced to a state of slush and measured
in the manner described in paragraph 42.

INSTKUCTIONS FOR COOPERATIVE OBSERVERS 21

58. In addition to this measurement by the gage, a measurement
will be made of the actual depth in inches of the snow on the ground.
Select a level place of some extent, where the drifting is least pro-
nounced, and measure the snow in at least three places. The mean of
these measurements will give the snowfall, which is to be entered in
the column of the report headed ** Depth of snowfall in inches"; and
whenever it is impracticable to melt the snow as described in the pre-
ceding paragraph, one-tenth of this mean will give an approximate
value in water for the show which could not be melted. This value
must be set down in the proper column of the report in precisely the
same manner as rainfall or snow melted in the gage. After having
once made a measurement of the snowfall, it is not desired that the
same snow be measured at each succeeding observation until it shall
finally disappear, except to get the actual depth of the snow on ground
for entry in the proper column. Any fresh snow, however, should be
measured and recorded after it falls.

59. If no rain, snow, or hail has fallen since the last observation,
make an entry 0.00 in the proper column. If the amount is too small
to measure, make the entry ^^Trace" or **T.''

MISCELLANEOUS PHENOMENA

60. Frost. — Occurrence of first and last frost of the growing season
should be specially noted.

The terms descriptive of frost will be as follows:

Lighty to indicate a frost that has no destructive effect, although
tender plants and vines in exposed places may be injured. Heairy,
to indicate a frost that in itself is severer than a light frost — that is,
the deposit of frost is heavier and the temperature falls to a lower
point, although the staple products of the locality may not have been
generally destroyed. Killing^ to indicate a frost that is generally
destructive of vegetation and the staple products of the locality.

61. Coronas. — These must be distinguished from halos. Coronas
are small circles, very commonly seen around the moon, due to rays
of light passing through a thin layer of cloud. Sometimes as many
as three small concentric circles may be seen whose diameters are
in the ratio 1:2:3. They are frequently colored, red being the
outside color. These colors are not the pure colors of the spectrum,
but rather those of the opal, and are caused by interference and not
refraction. A solar corona is not often visible, on account of the
dazzling brightness of the sun, but it may generally be seen by viewing
the sun through colored glass, or noticing its reflection in water.

62. Halos are large circles of about 45° or 90° in diameter — that is,
the diameter is equal to one-eighth or one-fourth the circumference
of the horizon. The colors are very feeble; the red is the inside

22 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

color. Halos arise from the presence in the atmosphere of minute
prisms of ice, and are due to refraction of Ught. Sometimes the halo
is intensified into two bright spots, one on each side of the central
lumuiary. These are called ** parhelia'' or ^^paraselenae" (mock suns
or mock moons), sometimes sun dogs. Still more compUcated opti-
cal phenomena are sometimes seen, though rarely except in high
latitudes.

63. Thunderstorms. — Thunderstorms 6 hours apart may be con-
sidered as separate storms.

Upon the occurrence of thunder, give as nearly as possible the times
of first and loudest thunder and its duration, being careful to note if
a. m. or p. m.

Give the direction from which the storm appears to be coming, as
shown by threatening sky, Ughtning flashes, or thunder peals. Also
the direction toward which it goes.

64. Tornadoes. — All the meteorological circumstances attending
these should be minutely noted; viz. the form and color of the clouds;
the direction and intensity of the wind ; the frequency, intensity, and
form of the Ughtning; the occurrence of hail, destructive effects, etc.

65. Auroras. — The date, hour, and minute of the beginning and
ending of auroras should be carefully noted, as well as the azimuth
of the base and the altitude of the extremity, and of the crown of any
arch of light.

Observers should be particular as to the date of the aurora; and
when it begins in the evening of one day and continues into the early
morning of the next day, it will be entered as occuring on the first
day, but its details will be given in the record as occurring between
the hours of its actual beginning and ending. Thus, an aurora that
began on the evening of the 12 th of January and continued until the
early morning of the 13th would be entered as the aurora of the 12th,
but its details would be recorded as occuring, for instance, between
the hours of 10 p. m. of January 12 and 2 a. m. of January 13.

66. General phenomena of climate. — Information of a general char-
acter relating to the growth of plants will be of value in determining
the climatology of a district.

67. Character of the day. — The general character of the day from
sunrise to sunset should be recorded as "clear'', when the sky aver-
ages three-tenths or less obscured; ** partly cloudy", when from
four-tenths to seven-tenths obscured; and "cloudy'', when more than
seven-tenths obscured. The average cloudiness from sunrise to
sunset may be estimated with considerable accuracy by noting the

INSTKUCTIONS FOB COOPERATIVE OBSERVERS 23

degree of cloudiness, on the scale given, as near sunrise as possible,
between noon and 1 p. m., and near sunset; add these and divide this
sum by 3 ; the quotient will be considered the average cloudiness.

When Ught fog, light haze, or light smoke has prevailed during the
greater part of the day, with three-tenths or less of clouds, its char-
acter should be recorded as ** clear'', but when dense fog, dense haze
or dense smoke has prevailed the character of the day should be
recorded as ** foggy", **hazy'', or ** smoky'', as the case may be
When the last-named conditions prevail, it is recommended that
observers note in the column headed ** Miscellaneous phenomena"
the duration of same, e. g., ** dense fog from early morning till 3:00
p. m. ", etc.

NOMENCLATURE

68. The great diversity in the usage of meteorological terms by
the daily press and meteorological observers makes it desirable to
adhere to the following:

The word "storm" will refer to a disturbance of the ordinary
average conditions or to unusual phenomena, and unless specifically
qualified may include any or all meteorological disturbances, such as
wind, rain, snow, hail, thunder, etc. This word may be qualified by
some peculiarity, e. g., sand storm, or dust storm (such as the
"simoon"), hot wind (such as the "khamsin", "foehn", or " Chi-
nook"), cold windstorm (such as the "norther" and the "pam-
pero"), cold rainstorm, and snowstorm (such as the "blizzard").

69. A hurricane or "typhoon" is a large storm, often several hun-
dred miles in diameter, within which violent winds circulate around
a center. The center of a hurricane or "typhoon" is a compara-
tively calm region, where sometimes the clouds break away and the
rain ceases; whereas the center of a thunderstorm is the region of
greatest intensity of wind, rain, or lightning.

70. A tornado is of very much smaller size, usually less than 2
miles in diameter, within which even more violent winds prevail.
In the typical tornado these violent winds circulate about a central
axis rapidly ascending at the same time, and forming a funnel-shaped
cloud, whose top is at the average cloud level; but there have been
classed as tornadoes many destructive winds, which are not circulat-
ing about such a funnel-shaped cloud or vertical axis, but which are
either blowing straight ahead on the earth's surface, as in the
"derecho", or straight-line wind, or which have a quasi rotation
around a horizontal axis, as in the blast that accompanies the front
of a "norther" or the gust in front of the heavy rain of a thunder-
storm. Endeavor should be made as far as possible to separate the
true tornado, which is rare, from the numerous destructive winds,
squalls, and gusts wliich are frequently called tornadoes, hurricanes,
cyclones, and other high-sounding names.

24 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

71. The term ** whirlwind'* is applied to any revolving mass of air,
and includes at one extreme the hurricane and at the other extreme
the dust whirl of our street corners.

72. A ^Vyclone'' is a mass of air circulating around a center.
The lower portion of the air near the earth's surface has a vorticose
movement toward a center, while the upper layers have a move-
ment from a center. The line joining the upper and lower centers is
the axis of the cyclone. The direction of rotation is the same in
both upper and lower layers. In the Northern Hemisphere this
rotation is said to be in a negative direction, or opposite to the diurnal
motion of the sun in azimuth, and opposite to the movement of the
hands of a watch lying with its face uppermost.

73. An ** anticyclone'* also is a mass of air circulating around a
center, but the lower layer of air has a movement out from a center,
and the direction of rotation is opposite to that of a cyclone, being
positive in the Northern Hemisphere.

74. The term ** cyclone'* and ** anticyclone** describe phenomena
that cannot be observed at a single station. They should, therefore,
not be used in the description of local phenomena; they represent
generalizations based upon the charting and study of winds and
clouds observed at many stations and should only be used when the
nature of the rotation of the winds has been clearly demonstrated or
can be safelv inferred.

75. The term ^^cyclonic winds**, **cyclonic system**, and **cyclonic
rotation** are equivalent to **cyclone.** The outer portion of a
cyclone generally has feeble winds and fair weather.

76. The terms **high** and *4ow** refer to areas in which baro-
metric pressure is above or below that of the surrounding country,
without reference to any normal values and without implying any
specific peculiarity as to winds or weather.

INSTHUCTIONS FOR COOPERATIVE OBSERVERS

§ , III

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INSTRUCTIONS FOR COOPERATIVE OBSERVERS

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INSTRUCTIONS FOR COOPERATIVE OBSERVERS 27

in. EARTHQUAKES AND INSTRUCTIONS FOR THEIR NONINSTRU MENTAL

OBSERVATIONS

IMPORTANCE OF EARTHQUAKE DATA

77. While really destructive earthquakes are unusual, only a few
occurring during the course of a year in any part of the world, tremors
strong enough to produce slight damage occur somewhere every few
days. Indeed, if we count all disturbances from the most destructive
to the feeblest, it would appear that the earth is seldom, if ever,
wholly at rest.

78. Some portions of the earth's surface are, as is well known, far
more frequently visited by earthquakes, both great and small, than
are certain others, but no place is entirely free from at least an occa-
sional shock. Hence, seismology, or the science of earthquakes and
their phenomena, is of some importance to everyone and of great
importance to many. Thus, to be specific and to confine attention
strictly to the obviously and eminently practical, we should know
the exact locations of those numerous breaks and weak vertical seams
in the earth's crust along which abrupt slipping and sliding (the
cause of nearly all earthquakes) most frequently occur, so that as
far as possible we may avoid them in the location of such permanent
structures as dams, irrigation channels, aqueducts, bridges, and even
ordinary houses.

WHY THE WEATHER BUREAU SHOULD COLLECT EARTHQUAKE DATA

79. In spite of the good it clearly would serve, there is, however,
no map of any country that gives at all fully the locations of earth-
quake breaks or faults, nor is the collection of the data essential to
the construction of such a map of any extensive section possible,
except through the long and constant cooperation of a large number
of observers widely scattered over the area in question.

80. If then the people of the United States are to be supplied with
such practical maps as would enable them to reduce to a minimum
their fears of and losses from earthquake disasters, the necessary data
obviously may most easily be collected by the Weather Bureau, since
it alone, of the various Federal scientific institutions, already has the
adequate personnel and necessary organization.

REQUEST FOR COOPERATIVE OBSERVERS

81. Although each of the Weather Bureau's regular stations,
approximately 200, will report all earthquakes felt, yet the territory
covered is so great that its seismic disturbances cannot adequately
be recorded without the aid of a large number of voluntary assist-
ants. Hence it is earnestly hoped that, so far as possible, all the
bureau's numerous cooperative observers will assist also in the
collection of seismological data, by reporting, on cards that will be

28 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

furnished for that purpose, the date, etc., of each earthquake that
they may experience. To each observer the labor will be exceed-
ingly light, and the time consumed only a few minutes in a whole
year, but the collected results will be permanent and extremely
valuable — absolutely essential to the construction of the maps in
question and exceedingly helpful in the explanation of many obscure
earthquake phenomena.

INSTRUCTIONS FOR THE COLLECTION OF EARTHQUAKE DATA

82. The particular earthquake data desired is indicated on the
question cards that will be supplied to all who take part in this
work, but the method of collecting and forwarding this information
to the central office for classification and study is explained by the
following instructions:

(1) Regular Weather Bureau stations will be communciated with
directly from the central office; cooperative stations entirely by, or
when necessary, through section centers.

(2) All routine communications on seismology directed to the
cential office will be enclosed in penalty envelops marked *^ Seis-
mology.^^

(3) Each regular Weather Bureau station and each cooperative
station that agrees to assist in this work will be furnished with a
supply of question cards.

(4) Each station, regular and assisting cooperative, will promptly
fill out and forward in a penalty envelop one question card for each
earthquake felt.

(5) The regular stations at Boston, Atlanta, St. Louis, Denver,
and San Francisco will also send to the central office such news-
paper clippings in regard to earthquakes in the United States as
may come to their notice.

(6) Each section center may supply question cards to other re-
liable persons in addition to the cooperative observers. This is
especially desirable in those portions of the countrj'^ which are either
subject to earthquake shocks or sparsely inhabited.

(7) An earthquake that produces any appreciable damage wall be
made the subject of a special investigation determined upon at the
time.

(8) All question cards collected by section centers recording the
occurrence of an earthquake will be promptly forwarded to the
central office.

INDEX

Paragraph

Address of station 49

Air, temperature of 1

Alcohol, in minimum thermometers 12

column detached 13, 14, 15, 31

reuniting column 16, 17, 18, 19

Anticyclone 73, 74

Auroras 47, 65

Black pigment for thermometers 45

''Blizzard" 68

Boxes, for shipping thermometers 44

Box support, for rain gage 35

Broken instruments, returning of 46

Bubbles in minimum thermometers 31

prevented by hanging up 21

reuniting column 16, 17, 18, 19

Carbon sheets for making records 49

Cards for reporting earthquakes 81, 82

forwarding to central ofRce 82

Catch of rain gage 33

"Chinook" 68

Climate, general phenomena of 66

Clippings, newspapers, of earthquakes 82

Constriction in maximum thermometers 9

Cooperative observer's meteorological record 47

Coronas 47, 61

Correcting mistakes in meteorological record 49

Communication with cooperative observers, conducting 82

Communications on seismology with central office, addressing 82

Clouds 67

Cyclones 72, 74, 75

Daily meteorological observations 47

Day, character of 67

Data comprising meteorological observations 47

earthquake observations 82

Defective maximum thermometers, ' * retreaters " 10

minimum thermometers, broken alcohol columns 13, 14, 15, 31

reuniting alcohol columns 16, 17, 18, 19

"Derecho" 70

Diameter of rain-gage receiver 34

tube 34

Discrepancies in readings of thermometers 52

"Dust storm" 68

Duties of making earthquake observations 81

Earthquake data 77 to 82

from outside sources 82

Earthquake districts, location of 78, 79, 80

30 INDEX

Paragraph

Earthquakes, importance of cooperative observations 81

intensity of 77

of appreciable damage 82

Erroneous temperatures, guarding against 11

Exposure of rain gage 3, 32

instrument shelter 3

thermometers 2

**Foehn" 68

Fog 67

Form 1009 Metl. (Observer's record) 49

Frost 47,60

light 60

heavy 60

killing 60

Funnel of rain gage 34

Gage, rain, catch of 33

description of 34

distance from shelter 3

exposure of 32

size of 34

snow, description of 34

Graduation marks, renewal of, on thermometers 45

Gusts 70

Hail 64

Halos 62

Haze 67

*'High" 76

Hurricane 69

Index of minimum thermometers 12

reading of 30

sticking of 13

Instruments, broken, returning of 46

Ivory black, use of, on thermometers 45

Keys for shelter locks 5

"Khamsin" 68

Legs or support for instrument shelter 4

Location of shelters 7

Location of station, change in 49

Locks for shelters 5, 6

''Low" 76

Lightning 63, 64

Map of earthquake districts 79, 80, 81

Marks, graduation, renewal of, on thermometers 45

Maximum thermometer 9

care in reading 11

description of 9

mounting 22, 24

new supports for 23, 26

wooden supports for 22

reading of 27

"retreaters" 10

setting of 25, 51

temperature 47

reading of 50

INDEX 31

Paragraph

Mean temperature 48

determining of, from plus and minus 53

Measuring rainfall, units of 36

Mercury in maximum thermometer 9

Meteorological record 49

Meteorological terms 68-76

Minimum thermometer 12

alcohol, column of 12

detached 13, 14, 15, 31

hanging up 21

index of 12

sticking 13

mounting 22, 28

reuniting columns of 16, 17, 18, 19

reading of 30

setting of 21,29,51

temperature of 47

reading 50

testing 21

Minus and plus temperature signs 53

mean of 53

Mistakes made in record 49

Mock suns 62

Mounting thermometers 22, 24, 28

Nails, objection to use of, in packing 44

Name of station, change in 49

Newspaper clippings of earthquakes 82

''Norther" 68,70

Overflow of rain gage 34

Observations desired 47

of earthquakes 81, 82

time of making 48

Packing thermometers 44

"Pampero" 68

" Parhelia or Paraselenae " 62

Phenomena of climate 66

miscellaneous 67

Pigment, black, for thermometers 45

Plus and minus temperature signs 53

mean of 53

Post-office address 49

Precipitation. (See Rain and snow.)

Processes of reuniting broken alcohol columns 16, 17, 18, 19

Quicksilver (see Mercury) 11

Rainfall, absence of, recorded 49, 59

catch of 33

measuring of 34,36,37,38,39

overflow of 34

record of 55

units of measurements 36

32 INDEX

Paragraph

Rain gage, catch of 33

description of 34

distance from shelter 3

exposure of 32

Rain gage, size of 34

Reading maximunoi thernoioineter 11, 27

minimum thermometer 30

thermometers, use of plus and minus signs 53

discrepencies in 52

Receiver of rain gage 34

Record of meteorological observations 47

Reports, preparation of 49

''Retreaters" 10

Roof exposure of rain gage 32

Sand storm 68

Screws, use of, in packing 44

Seismology (see Earthquakes) 77-82

"Setting " maximum thermometer 26, 52

minimum thermometer 21, 30,52

thermometers, test of correctness 52

Shelter, instrument 3

exposure of 7

height above ground S

installation of 4

legs or support of 4

locking of 54

locks for 5

''Simoon" 68

Smoke 67

Snowfall, measuring of 40,41,42,43,56,57,58,59

record of 56

units of measurement 56

Snow gage 34

Solar corona 61

Squalls 70

Station, location of, change in 49

r name of, change in 49

^ Stationery, for making records 49

Stick, measuring, for rainfall 36

' Supports, box, for rain gage 35

* maximum and minimum thermometers 3, 26

/ shelter 4

Temperature of free air 1

erroneous, guarding against H

maximum 47

reading of 27

mean 48

when plus and minus 53

minimum 47

reading of 34

Testing minimum thermometers for defects 21

INDEX 33

Paragraph

Thermometers, exposure of 2

broken, returning of 46

maximum. (See Maximum thermometer.)
minimum. (See Minimum thermometer.)

nonregistering (exposed) 53

packing of 44

setting of 21,25.29,51

test of correctness 52

time of 51

shelter for 3

shipment of 44

Thunderstorms 47, 63

Time of making observations 48

Tornadoes 47, 64, 70

" Townsend " thermometer supports, mounting of 23

oiling of 26

"Trace'' of rainfall 59

Tube, measuring, of rain gage 34

diameter of 34

"Typhoon" 69

Water measuring of, in rain gage 36, 37, 38, 39

Weather, state of 47

Whirling (setting) maximum thermometer 25

Whirlwind 71

Wind, disturbing effect on rain gage 32

intensity of, in tornadoes 64

Zero temperature reading 53

r-~-

U. S. DEPARTMENT OF COMMERCE

WEATHER BUREAU :: :: Washington, D. C.

Instructions for
Cooperative Observers

CIRCULARS B AND C, INSTRUMENT
DIVISION :: Ninth Edition {Revised 1941)

Thermometer slielter and rain gage for cooperative observer.

W. B. No. 843

UNITED STATES DEPARTMENT OF COMMERCE

WEATHER BUREAU

INSTRUCTIONS

FOR

COOPERATIVE OBSERVERS

CIRCULARS B AND C, INSTRUMENT DIVISION

NINTH DIVISION (REVISED 1941)

UNITED STATES

GOVERNMENT PRINTING OPFICE

WASHINGTON : 1941

For sale by the Superintendent of Documents, Washineton, D. C- --.--. Price 10 cents

CONTENTS

Page

Introduction 1

I. Instructions for the erection and care of instruments 2

The object of temperature readings and exposure of thermometers 2

General description of thermometers 6

Instructions for reuniting detached columns of alcohol 8

Instructions for mounting maximum and minimum thermometers 12

The rain gage 14

How to measure rainfall and snowfall 17

General instructions about instruments 19

II. To make and record observations 20

Temperature records 21

Precipitation records 22

Miscellaneous phenomena 24

Definitions 26

Form 1009, meteorological, sample monthly record 34

III. Earthquakes and instructions for their noninstrumental observation. 27

Importance of earthquake data 27

Why the Weather Bureau should collect earthquake data 27

Instructions for the collection of earthquake data 28

Index 29

ILLUSTRATIONS

Circular B & C, Instrument Division

(Ninth Edition)

Page

Thermometer shelter and rain gage for cooperative observers Frontispiece

Figure 1 . Details of support for small instrument shelter 3

Figure 2. Instrument shelter on support, showing angle anchors buried in

ground 4

Figure 3. Showing first process of reuniting alcohol column in minimum

thermometer 9

Figure 4. Showing second process of reuniting alcohol column in minimum

thermometer 10

Figure 5. Showing third process of reuniting alcohol column in minimum

thermometer 11

Figure 6. Setting maximum thermometer 13

Figure 7. Setting minimum thermometer 13

Figure 8. The maximum thermometer should be gently lowered to the

reading position 13

Figure 9. Rain gage, showing details of 15

Figure 10. Rain gage and box support 18

DEPOSITED BY TH^ ^.
ED STATES OF AMERICA

0CT29'4\

INSTRUCTIONS FOR COOPERATIVE OBSERVERS

OF THE WEATHER BUREAU

INTRODUCTION

The object of this pamphlet is to furnish cooperative observers
with instructions for their guidance in taking and recording meteoro-
logical observations, more especially of temperature and rainfall,
and for reporting earthquakes.

There are at this writing about 5,500 cooperative observers in the
United States. The records furnished by these observers are of great
value in affording information upon which many of the important
publications of the Weather Bureau are based, and it is a policy of
the Bureau to foster and encourage the keeping of such records. The
Meteorological Yearbook and the monthly and annual summaries of
the several sections of the climatological service of the Bureau con-
tain more or less complete sunmiaries of the observations, and through
their wide dissemination the public is furnished extensive and reli-
able data concerning the peculiarities of climate in every section of
the country. Besides the records mentioned above, the observers
furnish reports that form in part the basis of the Weekly Weather
and Crop Bulletin, which gives prompt information as to weather
and crop conditions during the principal growing season.

The cooperative observer who each day faithfully records the read-
ings of his instrument and notes the meteorological conditions pre-
vailing at his station is performing a valuable public service. The
publications in which his records appear are widely consulted by
persons seeking information regarding climate and weather.

Cooperative observers receive no money compensation for their
services, but they regularly receive such of the publications of the
Weather Bureau as can be furnished free of cost.

As the value of a meteorological record increases with its dura-
tion, continuity of record is of the utmost importance, and it is ur-
gently recommended that those who undertake to conduct observa-
tions endeavor to provide, as far as practicable, for an uninterrupted

2 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

series. A member of the observer's family, or other competent person,
should be fully instructed in the matter of taking and recording ob-
servations, SO that no break in the record will result from the tem-
porary absence of the observer or from his inability from any cause
to make the necessary observations.

For the purpose of securing these observations, the Chief of the
Weather Bureau is authorized by law to lend instruments to persons
willing to take the observations, on certain conditions. These con-
ditions, in the main, are the safe-keeping of the instruments, their
return to the Weather Bureau if for any reason the station is discon-
tinued, and the furnishing of copies of the observations to the section
director of the climatological service of the Weather Bureau for the
State where located, free of expense to the Government.

Cooperative observers are usually furnished with maximum and
minimum thermometers, instrument shelters, and rain gages, but not
with barometers or recording instruments; nor will instruments be
supplied when the proposed station is considered too near others
already established.

Cooperative observers who fail to comply with the conditions upon
which Weather Bureau instruments have been issued will be called
upon by the section director to return them.

Blank forms and franked envelopes are furnished free of expense
to the observers for transmitting reports to the section centers.

Observers willing to furnish the local press with meteorological
data for publication will be supplied with suitable postal-card forms,
properly addressed, upon application to the section director.

The cooperative observer is requested to fill up and forward to the
section center, as soon as the equipment is installed, a copy of Form
No. 4029 — ^Mis. (Description of cooperative observer's station and
instruments), and when any change is made in the location of instru-
ments to notify promptly the official in charge of the section center.

All correspondence relative to the work of a cooperative station
and requests for instruments, supplies, repairs, etc., should be ad-
dressed to the official in charge of the section center, who will furnish
such information as may be required and act promptly upon the
requests.

I. INSTRUCTIONS FOR THE ERECTION AND CARE OF INSTRUMENTS

THE OBJECTT OF TEMPERATURE READINGS AND THE EXPOSURE OF

THERMOMETERS

1. Temperature of the air, — The use of thermometers in meteoro-
logical observation is for the purpose of obtaining the tnie temperature
of the free air.

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 3

The air near the surface of the earth is nearly always in motion
and when not confined in a comparatively closed space the several
portions are thoroughly mixed and have nearly or quite the same
temperature. When any portion of the air is confined, however,
so that it cannot intermingle freely with the general air masses,
its temperature will be influenced to a marked extent by the local
surroundings and will not be a free-air temperature.

2. These ideas show us at once that if we intend to make observa-
tions of the real air temperatures our thermometers must, if possible,
be placed in an open space where the circulation of the air is quite
unobstructed. It will not do, however, to place the thermometers
simply in the open air, exposed freely to the sky and the direct rays

SC/f£W /fOLE^

Front or rear section. End view showing ties and brace.

Figure 1. — Details of support for small instrument shelter.

of the sun. The sunshine would cause the thermometer to register
too high, and even if not exposed directly to the sun it could not
be depended upon to indicate the true air temperature either day
or night.

3. Thermometer shelter. — ^To overcome these difficulties it is neces-
sary to employ a thermometer shelter. This is nothing more than a
wooden box painted white with louvred sides made in such a way that
the air can move through it with the greatest possible freedom.
This is an essential condition in thermometer exposure. The object
of the box or shelter is simply to screen off the direct and reflected
sunshine and the radiation to and from the sky and to keep the
thermometers dry.

4 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

To obtain the true air temperature, therefore, all thermometers
will be placed in a suitable shelter where the circulation of the air
is as free as possible.

The standard shelter for cooperative work is shown with its support
in the frontispiece. The maximum and minimum thermometers
mounted on the Townsend support are illustrated in figures 2 and 6.
The frontispiece shows also
the rain gage, but in order
to bring this into the picture
it was placed nearer the
shelter than it should be in
actual use. The rain gage
should be at least 16 or 20
feet from the shelter.

4. Installation of skelter
and support. — Shelters sent
to observers are assembled
complete ready to be set up,
and each shelter is usually
accompanied by a support
made up according to the
details given in figure 1.
The assembled support with
the shelter mounted thereon
is plainly shown in the fron-
tispiece and in figure 2. It
is occasionally better to ar-
range for a support to be
constructed locally. Four
substantia) posts, of mate-
rial known to last well in the
ground and long enough to
provide a good anchorage,
may be employed.

The instrument shelter
t sbowina support comes shipped
chrome er j^jj^^^g^j down, and must
be assembled as follows:
Make up each end section first as follows: Lay two legs on a floor
or other flat surface. There will be found on each leg a pencil mark
near the top and another near the middle on two adjacent sides of
the legs. Place the legs so that these marks are on top and on the
outside. A wide short girt, having two countersunk screw holes,
should be nailed to the two legs, the lower edge to the pencil line near
the top of the legs. It will be noticed that this girt extends 1 inch

INSTRUCTIONS FOR COOPERATrV'E OBSERVERS 5

beyond the top of the legs. This is to enable it when the support is
completed, to clasp the shelter and be screwed thereto. The short
lower girt will be nailed to the legs with its upper edge on the lower
pencil mark. The ends of both girts should be flush with the outside
of the legs. A short brace should then be nailed in position with
the lower end to right and with the beveled ends flush with the out-
side faces of the legs. It is suggested that the parts be laid down
before nailing, and that only one nail be driven at each joint until
after the brace is in position.

The two long upper girts can then be nailed on, their ends coming
out flush with the outside edges of the wide upper girts, and their
lower edges to the pencil lines. In a similar manner nail the two
long lower girts, their upper edges to the pencil lines and their ends
flush with the outside faces of the lower girts of the end sections.
Now nail the two long braces in position, left end lowermost, and if
the end sections were braced properly it will be found that the ends of
the long braces will meet and cover the ends of the short braces.

5. Steel shelter supports. — To provide a more rigid and lasting
support, steel supports have been procured locally on specifications
which may be obtained from the Instrument Division, if desired.
The corner posts of these supports may be footed in concrete or
otherwise weighted to prevent the overturning of the shelter in high
winds.

6. Locks for instrument shelters, — ^For many years all shelters
issued to stations from the Central Office have been furnished with
the same kind of lock and key (known as the No. 39). This is the
standard lock, and new keys can always be procured promptly on
application to the section center, where a small stock will be kept.

7. Location or exposure of shelter. — ^The location chosen should
meet the following requirements so far as practicable, having as the
objective the determination of the true maximum and minimum
temperatures at the elevation above ground of the thermometers,
nearly 4 feet 6 inches.

(a) Choose a level, open space or small clearing so that the ther-
mometers are ventilated so far as possible by the natural wind.
At the same time, consideration must be given to the convenience of
the observer, which requires the shelter to be reasonably close to the
observer's dwelling.

(6) The location should be, in general, typical of the near-by area
and not be unduly influenced by local conditions. While the ground

326040*— 41 — —2

6 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

beneath the shelter may be grass-covered, as a rule, being part of the
observer's premises, the air reaching the thermometers should be
representative of the surrounding area. This is of particular impor-
tance as regards the minimum temperature, which often occurs when
there is little or no wind. The character and color of the ground
surface influences the rate of loss of heat by radiation during clear
nights, so that the ground near to, if not directly beneath the shelter,
should be representative of the area in general ; or, the grass-covered
surface small enough not to seriously affect the temperature distribu-
tion. It should be borne in mind that during clear, calm nights the
lowest temperature is at or very close to the ground, while it will
often be considerably higher at the elevation of the thermometers in
the shelter.

Roof installations are undesirable but, if unavoidable, the shelter
should be located where heat from the building will influence the
temperature readings the least, and an open-board platform placed
beneath the shelter will usually be required to minimize the effect
of heat reflected from the surface of the roof.

GENERAL. DESCRIPTION OP THERM03IETERS

8. Before the observer attempts to set up the thermometers, let
him first examine them and compare them with the description and
familiarize himself with all the peculiarities of each, so that he may
understand which is the maximum and which is the minimum.

9. MaadmAjum thermometer, — The glass bulb and bore of a maximum
thermometer is always filled with mercury, sometimes called quick-
silver.

The most distinctive peculiarity of the maximum thermometer,
however, is not so easily seen. If the observer will hold the ther-
mometer vertically with the bulb down, he will notice that the mer-
curial column does not extend entirely into the bulb. A close examina-
tion of the thermometer at the point just above the bulb where the
mercurial column stops will show that the glass tube seems to have
been almost closed at that point. This is just what has been done,
and the passageway for the mercury is so fine at that point that the
mercury will go through only with some difiiculty. The observer
should next hold his warm fingers around the bulb. The mercury in
the bulb, expanding as it becomes warm, will then be forced to pass
the constricted portion of the tube, flowing through in little spurts.
When the fingers are removed from the bulb the mercury below the
constriction, contracting as it cools, withdraws toward the bulb, but
none of the mercury above the constriction goes back, and the length
of the column remains the same as it was when the bulb was warmest.
In this way the maximum temperature is registered.

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 7

If the thermometer is held in a horizontal position and then alter-
nately tilted — first with bulb higher than stem, then with bulb lower
than stem — it will be noticed that the thread of mercury may be made
to flow to either end of the tube as desired.

10. Retreaters. — Experience has shown that in spite of every care
in the inspection and testing of maximum thermometers, they will,
if exposed vertically, sometimes fail to record the maximum tempera-
ture; that is to say, the constriction in the bore of the tube is not so
fine as required, and when the temperature falls after reaching the
maximum point the mercury in the column of the thermometer with-
draws into the bulb and the record of the maximum temperature is lost.
Such thermometers are sometimes said "to retreat," and are called
"retreaters."

A good maximum thermometer may be made a retreater by a too
violent throw-down of the mercury, as explained in paragraph 24.

11. Since it is known that a maximum thermometer may become a
retreater without that fact being noticed, the safest procedure is to
mount it with the bulb a little higher than the stem, as shown in
figure 7. The support is so made that the angle of elevation of the
thermometer back is 5 degrees. In this position the column of mer-
cury is not under pressure, and when the thermometer is lowered
gently to reading position it will rarely fail to record the highest
temperature reached.

When it is desired to make a reading, the thermometer must be
slowly and carefully lowered to a position in which the mercwry rests
on the constriction. This reading position, or angle, is not the same
for all maximum thermometers, but rather should be determined by
tlhe observer watching the manner in which the mercury flows in the
tube at different angles of elevation. Greater care must be used with
high temperatures because of the greater weight of the long column
of mercury.

After reading, the thermometer should be set by whirling as
described in paragraph 24.

12. Minirwwm thermometer, — The bulb and bore of this thermom-
eter are always filled with alcohol, sometimes colored to aid visibility.
It is, therefore, at once distinguished from a mercurial thermometer.
Besides the alcohol, the bore of the thermometer contains an elongated,
dark-colored object, made of glass, having rounded heads on each
end. This object is called the index.

13. Generally the index will slide freely up and down the thermom-
eter tube when one end is raised or lowered. Sometimes, however,
and especially after the thermometer has been shipped, the alcohol in
the tube becomes broken up into short, detached columns and the
index is frequently caught and held.

8 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

14. Of course the thermometer caimot be used until this is reme-
died, which in some cases proves to be a diflBcult operation. Observ-
ers are requested to use special care in learning and following the
instructions given below and to notice carefully the several effects
so that they may judge for themselves as to what must be done to
unite detached columns and avoid the danger of breaking the
instrument.

The fact that vapor of alcohol condenses in the upper end of a
minimum thermometer is well known to those who handle a con-
siderable number of such thermometers. Manufacturers seal off such
thermometers under considerable air pressure in order to lessen the
probability of separation; but it will be apparent upon reflection
that when a marked fall of air temperature occurs, conditions favor-
able for condensation of the vapor of the alcohol coincide with lessen-
ing of internal pressure, due to increased space above the column.

Under such circumstances a good minimum thermometer is likely
to be misjudged as defective, when all that is needed to correct the
condition is to reunite the column, then hang it in a vertical position
for an hour or more so that the alcohol adhering to the walls may
drain down. The test for the success of the effort is simple — ^merely
to set the thermometer, immersed up to the reading point in melting,
shaved, pure ice, or snow. Within an hour or so it should read very-
close to 32°.

15. The many different ways in which the alcohol column becomes
separated make it impossible to unite it by any single method, different
methods being required not only for different conditions but also for
different thermometers.

Frequently there are only a few short, detached portions near the
top, and the index slides freely along the lower portion of the tube
and drops into the bulb. Again, the detached columns are found all
along the tube, and the index is caught and held at some point above
the main column. In such a case it is advisable first to bring the
index into the bulb as follows :

16. First process, — ^Hold the thermometer lightly between the
thumb and fingers and strike the lower end of the metallic scale
against the top of a table or other firm object, as shown in figure 3,
first, however, interposing one or two thicknesses of cloth or several
folds of paper, so as not to produce too severe a shock upon the ther-
mometer. The taps of the thermometer should be made lightly at
first and the index examined to see if it has moved along the tube
even a little distance, as can be told by noticing the exact position
of the index in reference to the graduations on the tube. If several
taps fail to move the index, increase the force of the taps a little at a

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 9

time until tlie index starts, after which repeat the operation until the
index gets within the continuous column. Here it will fall of its
own weight into the bulb. Generally this will be all that is necessary
to place the index in the bulb. Sometimes the detached column will
also have been partly or wholly united. If the column is still broken
in places, the observer should try a few more taps, and examine quickly
in a very careful manner. Small portions of the alcohol will gener-
ally be seen slowly moving along the sides of the tube toward the
main column, and a continua-
tion of the taps will unite the
columns. In some cases 15 or
20 minutes may be required to
completely unite broken col-
umns. If, however, the index
cannot be made to move with
quite hard taps, or the columns
cannot be united, it is advisable
to try some of the methods
described next, being careful
always to avoid carrying any
process so far as to endanger
breaking the thermometer.

17. Second process. — This
method will not loosen the in-
dex, but may unite the detached
columns. Grasp the thermome-
ter securely a little below the
middle, with the bulb end down,
and strike the edge of the metal
back opposite the broken col-
umn sharply against the fleshy
portion of the palm of the other

r , ■, t'lGtKB a.— SliuiviiifC first pi-oi-een ut reuniting

hand, or, if necessary, against aieohol <^oiumn h, nilnlmum themiompter.

a small block of wood held in

the hand. (See fig. 4.) A continued Jarring in this way often causes
the alcohol to run down, though in many cases a large number of
taps are necessary. Observers should therefore not give up if the
column does not unite at once, but should watch very closely for
the movements of small portions of alcohol along the sides of the
tube. Here, again, care must be used not to strike too hard and to
hold the thermometer by the metal back in such a manner as not
to squeeze or press against the stem of the thermometer itself. When
the bore of the thermometer is large, the above process is almost

10 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

sure to unite the column. Good results are also obtained with ther-
mometers of fine bore, though the latter, even in skilled hands, often
require a half hour or more of time if the column is badly detached.
18. Third process. — This method can also be used in place of those
above and is sometimes effective in forcing the index into the bulb.
Grasp the thermometer a little above the middle, clasping the fingers

FIGUHU 4.— SbowUis f

and hand firmly against the edges of the metallic back, but not so
as to bring any pressure upon the glass tube, which should be turned
toward you and with the bulb uppermost, as shown in figure 5. With
the thermometer in this position and about as high as the head and
the arm free from the body, quickly lower tlie arm and hand a foot
or more, turning the wrist at the same time, so that the bulb of the
thermometer describes a somewhat circular path downward through
the air, stopping the motion with a sudden jerk just as the ther-

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 11

mometej- is vertical. If the thermometer is grasped properly, a
very violent motion can be given in this way without danger. It will
sometimes be necessary to repeat the operation a considerable num-
ber of times to entirely unite the detached columns.

19. Fourth process, — A. modification of the swinging process just
described consists in whirling the thermometer rapidly on a short
string. For this purpose a stout string is passed through the hole
in the top of the metal back of the thermometer. This is left double
and firmly grasped at a

distance of 6 or 8 inches
from the thermometer,
which may then be given
a very rapid whirling
motion. Considerable
care and practice are re-
quired to whirl the ther-
mometer rapidly and
stop it safely. This
method will, however,
often bring down the in-
dex and unite detached
columns.

20. If observers are
unsuccessful after care-
fully following the above
instructions, the matter
should be reported to the
section center, giving
full particulars as to
what has been done.

21. Testing mini/rmmb

., J o FiGi'BE 5. — SLowlng tdltd proceaa of reuoltlng aleoUol

therTnoTmter.— Some one ^.„i„„„ ,„ ,„i^i,„„^ thermometer.

or more of these proc-
esses should in nearly ail instances be sufficient to unite any detached
column, and when all the bubbles have been removed the observer
can then see how the instrument works. Hold the thermometer
vertically and warm up the bulb by holding it in the hand; then turn
the instrument upside down. Watch the index as it glides along the
tube; when it strikes the top of the column it will at once stop. This
operation of bringing the index to the top of the colmun is called
"setting" the thermometer.

Next hold the thermometer horizontally. As the bulb cools off
the index will be dragged backward toward the bulb, but always
remains at the end of the column of alcohol. It is a good plan to
hasten the cooling by placing a little wet cloth or piece of ice against

12 IXSTRUCnOXS for COOPERAXn-E OBS£R\^RS

the bulb. When you have watched the index go down with the
column, warm the bulb again with the hand. The column will go up
immediately, but the alcohol will flow around the index and leave
it at the lowest point ; that is, the index remains so that its top end
is at the lowest point reached by the alcohol column, and the mimnnnii
temperature is indicated in this way. The thermometer must be held
horizontally throughout these operations.

When the thermometer is not in use for observation, it is a good
plan to hang it up, as bubbles are less likely to form in the tube in
this position.

The thermometer should also be maintained in a vertical position
for several hours after a broken column has been united to permit any
alcohol clinging to the sides of the bore to drain down.

INSlKUCnONS FOR MOUNTING MAXIMUM AND MINIMUM THERMOMETERS

22. The Tovm^end thermometer support, — This support, with ther-
mometers attached, shown in figures 6 and 8, should be firmly screwed
to the cross board of the instrument shelter, approximately in the
middle, and with the legend "U. S. W. B." right side up.

23. MttximumA thermjometer. — ^Mount the maximum thermometer
on the carrier on the loTig projection stud, and clamp it just below the
upper strap, and with the bulb at the left, so that it over-balances and
tends to hang bulb end down.

24. To whirl and set the maxim/umA therm/)meter. — ^Release the pawl
fixed near the base of the maximum pin. This unlocks the carrier.
Place the finger, or pencil, at one side of the thermometer scale and
impart to it a rapid rotation, as suggested by the dotted line and
arrow in figure 8. Allow the thermometer to whirl until it comes
to rest itself. Do not try to stop it while whirling. Note carefully
whether or not the space between the bulb and constriction is filled
with mercury. Repeat the whirling, if necessary, until the column is
whirled down as far as it can go.

The space in the bore of the tube not occupied by the mercury is
a vacuum. Hence, the mercury should rest upon the constriction
when whirling is started. Otherwise its violent throwdown may
fracture the glass constriction. When such internal fracture has
occurred it will be apparent as an irridescent patch in the neigh-
borhood of the constriction when the thermometer is examined by
reflected light.

IXSTRUCTIONS FOR COOPEBAXnE OBSERVERS

E 7. — Illustrating Betting ot mlnl-

I'tMl i»Hitlan until tLe Index (ullB
lie end of the coliiniu.

14 IXSTRUCTIONS FOR COOPERATIVE OBSERVERS

25. The revolving carrier for the maximum thermometer must be
oiled occasionally through the hole in the side provided for the pur-
pose so that the carrier will revolve easily. A thin, nongumming"
oil should be used.

26. To read the maxirwwirb thermometeT. — ^First carefiuUy dis-
engao^e the pawl that holds the maximum thermometer, then slowly^
lower it, as shown in Fig. 8, bulb end down, until the mercury rests
on the constriction. The thermometer must not be lowered sud-
denly, especially in warm weather, as the weight of the long column
of mercury is likely to force some portion through the constriction
and cause an erroneous reading. The maximunh temperature is the
scale reading at the top of the colwmn of mercury.

27. Mounting minimum thermometer, — The minimum thermom-
eter must be mounted in the support on the short projecting stud.
Clamp the thermometer as shown in the support at about two-thirds
of the thermometer length as measured from the bulb end, with the
huJh end to the left,

28. To set the minimum thermx)meter, — Turn the carrier and ther-
mometer to a vertical position, bulb uppermost, and allow the index
to fall to the end of the column. After setting do not fail to turn
the minimum thermometer back to its nearly horizontal position, as
shown in figure 8.

29. To read the minimum therm/mieter, — The minimum thermom-
eter must always be read while it is still in its horizontal position as
left after setting at the previous observation. To avoid possible dis-
placement by vibrations, the minimum thermometer must be read
before whirling and setting the maximum thermometer. The read-
ing is obtained by noting the number of degrees on the scale opposite
the end of the index farthest from the huTb, A reading taken at the
end of the spirit column will give the current termperature.

30. If at any time the column is found to be broken and bubbles
are observed in the tube the instrument should be taken off the
supports and an effort made to unite the column by some of the
methods already described.

THE RAIN GAGE

31. The exposure of the rain gage is a very important matter.
The most serious disturbing effect in collecting rainfall is the wind.
In blowing against the gage the eddies of wind formed about the
mouth tend to carry the rain away, so that frequently too little is
caught in the gage.

Weather Bureau officials will therefore take particular care in
selecting a place for the location of the gage, as the value of the

IXSTRUCTIONS FOR COOPERATIVE OBSER\"ERS 15

records is sometimes greatly impaired by improper exposure. It
is scarcely necessary to say that every precaution should be taken
to protect gages from the interference of animals and unauthorized
persons. Select, if possible, a position in some open lot, unobstructed
by large trees, buildings, or fences. Low bushes and fences, or walls
that break the force of the wind in the vicinity of the gage, are,
however, beneficial, if at a distance at least twice as great as the
lieight of the object. Such surroundings, in general, afford the best
exposure. Gages should be exposed upon roofs of buildings only

yirticttZ SeaUark

when ground exposures are impracticable, and then the roof should
be flat, or nearly so, and the middle portion should be selected to
get the best results.

32. Kain gages in slightly different positions, if badly exposed,
catch very different amounts of rainfall. Within a few yards of
each other two gages may show a difference of 20 percent in the
fall in a heavy rainstorm. The stronger the wind the greater the
difference will be. In a high location eddies of wind produced
by walls of buildings divert rain that would otherwise fall in the
gage. A gage near the edge of the roof, on the windward side of a
building, sliows less rainfall than one in the center of the roof. The

16 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

vertical, ascending current along the side of the wall extends slightly
above the level of the roof, and part of the rain is carried away from
the gage. In the center of a large, flat roof, at least 60 feet square,
the rainfall collected by a gage does not differ materially from that
collected at the level of the ground.

33. Wind Shields, — ^In windy locations, as before mentioned rain
and snow gages give a more or less deficient catch, unless aided by
fortuitous features of topography, and gage location, with respect
to structures which shield the gage from the wind in varying degrees.
Shields for precipitation gages made of metal or cloth have lonfx
been known to be effective in securing a reasonably normal catch,
and are needed especially for snowfall.

Shields of various type have been used quite extensively in ex-
periments carried out in the State of Utah and have been found to
be distinctly beneficial ("Shielded Storage Precipitation Gages,"
by J. Cecil Alter, Monthly Weather Review, July 1937). They con-
sist essentially of a circular metal frame from which are suspended
wedged-shaped pieces of thin metal, free to be deflected inward by
the wind about their suspension. The wind is thereby deflected
downward at the windward side of the gage, resulting in a normal
instead of an accelerated wind speed over the top of the gage in
the absence of shields. When the wind speed over the gage is not
accelerated the precipitation enters the receiver instead of being
blown past the gage to the lee of the gage where an excess would be
deposited.

34. Description of rain gage, — The rain gage consists of the fol-
lowing parts:

The receiver A;

The overflow attachment B;

The measuring tube C,

The top cylindrical portion of the receiver, marked a in figure 9,
is exactly 8 inches in diameter, inside, and is provided with a funnel-
shaped bottom, which conducts any precipitation caught in the re-
ceiver into the tall cylindrical measuring tube, C^ the total height
of which, inside, is exactly 20 inches. The diameter of this tube is
much smaller than the large receiving tube, a^ being only 2.53 inches.
In consequence of this a small amount of rain falling into the receiver
and flowing into C fills the latter to a depth greater than the actual
rainfall in proportion as the area of the receiver is greater than the
area of the measuring tube. In the standard gages of the Weather
Bureau the depth of the rainfall, in accordance with this principle, is
magnified just 10 times. The receiver, A^ has a sleeve, c?, figure 9,
which slips over the tube, C^ and very effectually prevents any loss of
rainfall. Again, when the rainfall is very heavy, the tube, C^ may

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 17

overflow. In this case, to prevent loss, a little opening, shown at
6, figure 9, is made in the sleeve, tZ, just on a level with the top of
the tube, G. The excess of rainfall escapes through this opening, and
is retained in the large overflow attachment, 5, and can be measured
afterwards, as will be described later. The opening e is omitted in
the latest forms of gages, as the water easily flows between the sleeve
and the tube (7, which fit each other loosely. The inside diameter
of the overflow attachment is just 8 inches, and this portion of the
instrument can be used as a snow gage, as will be explained hereafter.

35. Ram-gage support, — ^The box in which the gage is shipped to
the observer is expressly designed as a stand for the instrument, and
should be opened at the head, which is fastened by screws. Set the
box as nearly vertical as possible at the place selected for exposure
and secure it in this position by driving down four stakes alongside,
in the manner indicated in figure 10. Care must be taken to have the
gage held in a truly vertical position. Slip in the head and lower it
to the level of the screw holes in the sides of the box about 10 inches
from the bottom, where the head will be securely fastened with the
screws taken out in opening the box. The gage can now be placed
inside, and appears as shown in figure 10. Separate the botttom of
the box support from the ground sufficiently to prevent rotting of
the wood.

More durable supports have occasionally been substituted for the
box support, but the wooden support protects the gage somewhat
from the sun's rays and thereby mostly prevents the loss through
evaporation of a small part of the rainfall which may have fallen.

HOW TO MEASURE RAINFALL AND SNOWFALL

36. Rainfall. — The measuring stick of the rain gage is graduated
into inches and tenths. Remembering that the actual depth of the
rainfall is magnified 10 times, as explained above, it is plain that if
we find the water 10 inches deep in the measuring tube, then the ac-
tual rainfall must have been only 1 inch deep, or if the water in the
tube is only one-tenth inch (or written as a decimal, 0.1 inch) deep,
then the rainfall must have been only one-hundredth inch (or
written as a decimal, 0.01 inch.)

37. The depth of the water is measured by inserting the measuring
stick into the gage through the small hole in the funnel. When the
stick reaches the bottom of the measuring tube it should be held for a
moment and then quickly withdrawn and examined to see at what
division of the graduation the top of the wet portion comes. The
numbering of this division, as stamped on the sticky gives, as has just
been explained, the actual depth of rainfall, and in making out rec-
ords and reports observers should always use the decimal expressions.

18 IXSTRUCTIONS FOR COOPERATIVE OBSERVERS

38. After measuring and recording in this way the precipitation
found in the gsige, the top should be i-emoved, the measuring tube
emptied and drained, and the gage put in position again. Observers
should be careful after emptying the gage to replace the measuring
tube so that the bottom stands within the ring in the middle of the
bottom of the overflow, and in putting on tlie receiver that it passe?;
over the measuring tube and rests squarely down upon the overflow.

39. When the amount of rain that has fallen more than fills the
measuring tube, some care is required to determine the total rainfall-
First, carefully remove the receiver so as not to spill any of the water

in the measuring tube, which
should be exactly full. If some
water has been slopped out and
the measuring tube is not ex-
actly full, the amount of water
remaining must be accurately
measured with the stick, as
already described. The tube is
then lifted out slowly and care-
fully, so as not to spill any of
the water into the overflow,
emptied, and allowed to drain
a moment or so. The water
remaining in tlie overflow is
now poured into the measuring
tube, care being taken not to
lose any, and measured in the
usual way, Suppose we find
FiGUiiB 10 — Rain gag,, nnii bux Buppoii ^his to be 0,47 inch rainfall;

then, remembering that the
measuHng tube is just 20 inches high, the total rainfall will be 2
inches + 0.47 inch=2.47 inches. Or, in case some water was spilled
from the measuring tube, the 0.47 inch should be simply added to
the first measured amount to give the total rainfall,

40. Snowfall. — During the winter season, especially in those cli-
mates where the precipitation is nearly all in the form of snow, the
overfiow attachment only of the rain gage should be exposed in the
support as a snow gage, Eemove the receiver and measuring tube to
(he house, as these parts cannot be used for measuring snow, and
even if rain should occur it is very apt to be frozen while in the meas-
uring tube, generally bursting it and rendering it worthless or highly
inaccurate.

41. First method. — Tlie snowfall collected in the overfiow attach-
ment is measured after placing the vessel in a warm room until the

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 19

snow is melted. The water is then carefully poured into the meas-
uring tube and measured just as though it were rainfall.

42. Second method, — ^The first method is objectionable, because It
often requires considerable time, and is liable to be inaccurate, owing
to the loss of the snow or water by evaporation. The following plan
is much better, unless clumsily conducted so as to spill and waste
the water: Take the overflow into the room and pour into it care-
fully one measuring tube full to the brim with water, preferably warm
water. This, in general, will mostly melt, or at least reduce to a
very fluid slush, a considerable snowfall. The measuring tube should
be again carefully filled to the brim from the melted contents of
the overflow and emptied; whereupon the remaining water in the
overflow should be carefully measured in the measuring tube, thus
giving quickly and easily the depth of melted snow.

43. The amount of snow collected in the overflow of the rain gage
is likely to be greatly deficient when the wind blows during the snow-
fall. In such cases it will be much better if the observer will discard
the snowfall in the overflow, empty it out and cut out a section of the
snow in an open place where the depth truly represents the precipi-
tation. This section is to be taken by plunging the empty overflow,
mouth downward, in the snow so as to cut out a cylindrical portion
the size of the overflow and the depth of the snow. By the use of a
thin board or other means it will not be difficult to gather up the com-
plete section of snow inside the overflow, after which it should be
reduced to slush and measured as already explained.

GENEILVL INSTRUCTIONS ABOUT INSTRUMENTS

44. Shipment of thermometers. — ^The boxes and packing material
received with thermometers should be carefully preserved for use in
returning instruments.

45. Care of thermometers^ and support, — ^When, from action of the
weather and long exposure, the graduation marks, figures, or letter-
ing on the glass tube, or metallic back of a thermometer are oblit-
erated or illegible, they can easily be renewed by the application of a
small quantity of artists' black pigment (ivory black). The best
method of applying the substance is to put a drop on a small stick,
such as a match, and rub it across the marks or lettering until the
spaces are thoroughly filled. The superfluous pigments should then
be wiped off with a piece of tissue or blotting paper in such manner
as not to draw the pigment from the lines.

20 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

The thermometer support shoukl be watched to see that the ther-
mometers are securely held by the set screws and shims when used.
This attention should prevent a considerable breakage of ther-
mometers, especially the maximum.

46. Care of gages^ shelters^ etc, — The rain and snow gage should
be critically inspected now and then to see that neither the measuring^
tube nor the overflow leak. Any such defect will be promptly
reported to the section director, as will also the need for the repair,
repainting, or replacement of the shelter and support, or the rain-
gage support.

47. Action to take when instruments are broken. — ^When from anv
cause instruments are broken they should be promptly returned,
with an explanation, to the section center.

Ordinary precautions are required in the use of instruments, and
observers are requested to use every reasonable care to avoid acci-
dents, breakage, and loss.

II. TO MAKE AND RECORD OBSERVATIONS

48. Ohservatio7is desired. — ^It is requested that cooperative observ^ers
make and record, daily, observations of the maximum and minimum
temperatures; precipitation (rainfall or snowfall); the state of the
weather (that is, the general character of the day from sunrise to
sunset), and such other miscellaneous phenomena as fog, frost, coro-
nas, thunderstorms, hail, sleet, tornadoes, and auroras.

Form No. 1009, furnished by the section centei^, is arranged to
facilitate recording the data desired by the Weather Bureau.

49. Time of making observations, — ^But one observation in each 24
hours is necessary on the part of cooperative observers, since the aver-
age of the readings of the maximum and minimum thermometers
gives an approximately correct mean temperature for the day.

Uniformity as to time of taking observations is desired. A definite
hour should be determined upon and the observations made each day
as near that hour as possible. About sunset is recommended as the
most satisfactory time for making the record, as the thermometers
will then, except under unusual conditions, register both maximum
and minimum temperatures for the day. The time at which obser-
vations are taken should invariably be noted on Form No. 1009.

50. Form No, 1009^ meteorological monthly record, — At the end of
this pamphlet will be found a copy of the form used by cooperative
observers for recording observations, with data properly filled in to
show how observations should be recorded. The instructions on the
cover of a book of WB Form 1009, similar to those here given, should
also be carefully followed.

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 21

It is particularly important, in the interest of accuracy, that the
observations be recorded as soon as made, and that the entries be
made day by day as observed. Even if no rain has fallen the ob-
server should bear in mind that his official record of that fact is as
important as the record of rainfall.

Special care should be exercised in the preparation of reports;
pencils should be kept sharp, and good carbon paper used to insure
satisfactory duplicate copies. Three copies of the report should be
made, one to be retained by the observer and two to be sent to the
section center on the first of each month. To make three copies of
the record requires two carbon sheets; these should be placed between
the forms, carbon side facing the form on which the record is to be
made, and an ordinary pencil — one not too soft — ^used in writing.
If a mistake occurs in recording, attempt should not be made to write
over the figures; draw a line through the incorrect entry and make
new figures either to the right or left, or on the margin of the form.

When the carbon paper no longer makes clear duplicates, ask for
a new supply. It is the wish of the Chief of the Weather Bureau to
keep cooperative observers well supplied with all material pertaining
to their official duties, and they are requested to make timely requisi-
tions therefor on their respective section centers.

When the name of the station and its post office are not the same,
both should always be entered on Form No. 1009, the name of the
station at the top of the form, and any change in location or name
of the station should be explained by note.

TEMPERATURE RECORDS

51. The readings of the maximum and minimum thermometers
should be made as explained in paragraphs 26 and 29 and recorded in
the appropriate columns of Form No. 1009.

Enter temperatures to the nearest whole degree. When the tem-
perature is an even number of degrees with an additional half degree,
e. g., 76i/2°9 drop the half and enter 76°. When an odd number and
a half degree, e. g. 731^°, enter 74°, the next higher whole number.

In recording maximum and minimum temperature the following
should be borne in mind. The maximum temperature of any day
cannot he lower than any of the following readings : (1) The minimum
of the previous day; (2) the minimum of the same day; (3) th'e mini-
mum of the following day; (4) the set maximum of the preceding
day ; (5) the set maximum of the same day.

The Tninvmum temperature of any day cannot he higher than (6)
the maximum of the preceding day, (7) the maximum of same
day, (8) the maximum of the following day, (9) the set maximum
of the day before, (10) the set maximum of the same day.

22 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

52. Thermometers set, — ^Immediately after the thermometers have
been carefully read and the values noted on the form, they should be
set; first noticmg, however, that both thermometers are in their
proper position and are securely fastened to their supports.

The maximum should be whirled and set first, and the minimum
neirt. In no case should the thermometer be set, except once each
day^ just after making the observation.

53. Test, — After setting the thermometers, the readings of the top
end of the index of the minimum thermometer and the top of the
mercurial column of the maximum should give the same temperature
generally within a fraction of a degree. If the difference is a degree
or more, and it cannot be corrected by resetting, it is possibly due to
bubbles in the minimum thermometer or slight displacements of the
alcohol. Persistent discrepancies of this sort should be reported to
the section center, and observers are requested to have this test in
mind and apply it frequently in order to detect this source of
inaccurate records.

54. Plus and minus signs. — Temperatures below zero are written
with the minus sign prefixed, thus: —1, —2, —4, etc., all indicating
that the temperature is below zero. If the temperature is exactly
zero, it should be recorded 0. Temperatures above zero are recorded
simply 2, 45, etc., as the case may be, it being understood by the
absence of any sign that it is ( + ) , or above zero.

In determining means when there are minus (below-zero) tempera-
tures, the sum of the minus readings is deducted from the sum of
the plus readings and the remainder divided by the number of days
in the month, imless one or more days' records are missing, when,
of course, those missing days are deducted from the divisor.

If the sum of the minus readings is greater than the sum of the
plus readings, the latter is subtracted from the former and the
remainder divided, as above. The resulting mean is a minus
temperature.

The preceding remarks about the computation of monthly means
is given only for information. Present practice requires the ob-
server to enter sums only, the means being computed afterward at
the section center,

55. Shelter locked, — The shelter should be carefully locked after
taking each observation in order to prevent unauthorized persons
from interfering with the instruments.

PRECIPITATION RECORDS

56. Rainfall, — ^Measurements of rainfall should be made at the
time of regular observations, and the gage should be emptied of all

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 23

the water it may contain as soon as it has been measured and the
parts replaced in readiness for the collection of the next rainfall.
The amount of rainfall will be determined as explained in paragraphs
37, 38, and 39.

57. Snowfall, — Snowfall is measured both in terms of the depth
of water equivalent and also by the thickness of the layer of snow-
fall on the ground. Wlien the water equivalent can not be deter-
mined accurately by melting, as given in paragraphs 41-43, inclusive,
as a last resort, take one-tenth the average measured depth of the
snowfall on a level, open place as the water equivalent of the snow-
fall; for example, 10 inches of snow squals 1 inch of melted snow
or water. Some estimate of the wetness or density of the snow
should be made, for the relation between the depth of snow and
depth of water equivalent varies widely in different storms, depending
on the wetness of the snow. It is, therefore, always best if possible
to reduce snow to a liquid condition for measurement, and the
simplest way to do this is to add to it a known volume of water
sufficient to change it to a state of slush, as explained in paragraph 42.
For each entry in the column 7 of Form 1009, headed "Snowfall,
inches and tenths," there must be an entry in the column 6, "Amount."
For rainfall, only one entry is made; for snowfall, two, one of which
is the depth of the snow, the other the depth of the water obtained
by melting the snow.

68. In the winter season the overflow only of the gage should be
exposed, as stated in paragraph 40, and the snow collected therein
between observations (or, better, a section of snow cut out, as
explained in paragraph 43) should be reduced to a state of slush
and measured in the manner described above and in paragraph 42.

59. In addition to the entry of the 24-hour precipitation as the
water equivalent of the snowfall, column 6 in WB Form 1009, the
snowfall in inches and tenths, is itself entered in column 7, and also
the total depth on the ground at time of observation, column 8.
This latter measurement is made by taking the mean of the depths
at three or more places least affected by drifting. Sometimes, in the
absence of more accurate determinations, the average depth of the
24-hour snowfall is used to obtain the entry for columns 6 and 7, using
Vioth of the snowfall depths as the water equivalent. This value
must be set down in column 8 of the report in precisely the same
manner as rainfall or snow melted in the gage. After having once
made a measurement of the snowfall, it is not desired that the same
snow be measured at each succeeding observation until it shall finally
disappear, except to get the actual depth of the snow on ground
for entry in the proper column. Any fresh snow, however, should be
measured and recorded after it falls.

24 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

60. If no rain, snow, or hail has fallen since the last observation,
make an entry 0.00 in the proper column. If the amount is too small
to measure, make the entry "Trace" or "T."

MISCELLANEOUS PHENOMENA

61. Frost, — Occurrence of first and last frost of the growing season
should be specially noted.

The terms descriptive of frost will be as follows :

Lights to indicate a frost that has no destructive effect, although
tender plants and vines in exposed places may be injured. Heavy^
to indicate a frost that in itself is severer than a light frost — ^that is,
the deposit of frost is heavier and the temperature falls to a lower
point, although the staple products of the locality may not have been
generally destroyed. Killing^ to indicate a frost that is generally
destructive of vegetation and the staple products of the locality.

62. Coronas. — These must be distinguished from halos. Coronas
are broad bands of light, very commonly seen around the moon, due
to rays of light passing through a thin layer of cloud. Sometimes
as many as three small concentric circles may be seen whose diameters
are in the ratio 1:2:3. They are frequently colored, red being the
outside color. These colors are not the pure colors of the spectrum,
but rather those of the opal, and are caused by interference and not
refraction. A solar corona is not often visible, on account of the
dazzling brightness of the sun, but is may generally be seen by view-
ing the sun through colored glass, or noticing its reflection in water.

63. Halos are large rings of about 45° or 90° in diameter — ^that is,
the diameter is equal to one-eighth or one-fourth the circumference
of the horizon. The colors are very feeble; the red is the inside
color. Halos arise from the presence in the atmosphere of minute
prisms of ice, and are due to refraction of light. Sometimes the halo
is intensified into two bright spots, one on each side of the central
luminary. These are called "parhelia" or "paraselence" (mock suns
or mock moons) , sometimes sun dogs. Still more complicated opti-
cal phenomena are sometimes seen, though rarely, except in high
latitudes.

64. Thvmderstorms, — Thunderstorms 6 hours apart may be con-
sidered as separate storms.

Upon the occurrence of thunder, give as nearly as possible the times
of first and loudest thimder and its duration, being careful to note if
a. m. or p. m.

Give the direction from which the storm appears to be coming, as
shown by threatening sky, lightning flashes, or thunder peals. Also
the direction toward which it goes.

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 25

65. Tornadoes, — ^AU the meteorological circumstances attending
these should be minutely noted, viz, the form and color of the clouds ;
the direction and intensity of the wind, direction of movement and
width of path, the frequency, intensity, and form of the lighting;
the occurrence of hail, destructive effects, etc.

66. Auroras, — The date, hour, and minute of the beginning and
ending of auroras should be carefully noted, as well as the azimuth
of the base and the altitude of the extremity, and of the crown of any
arch of light.

Observers should be particular as to the date of the aurora; and
when it begins in the evening of one day and continues into the early
morning of the next day, it will be entered as occurring on the f/rst
day, but its details will be given in the record as occurring between
the hours of its actual beginning and ending. Thus, an aurora that
began on the evening of the 12th of January and continued until the
early morning of the 13th would be entered as the aurora of the 12th,
but its details would be recorded as occurring, for instance, between
the hours of 10 p. m. of January 12 and 2 a. m. of January 13.

67. General phenomena of climate. — ^Information of a general char-
acter relating to the growth of plants will be of value in determining
the climatology of a district.

68. Charaxiter of the day, — The general character of the day from
sunrise to sunset should be recorded as "clear," when the sky aver-
ages three-tenths or less obscured; "partly cloudy," when from
four-tenths to seven-tenths obscured, and "cloudy," when more than
seven-tenths obscured. The average cloudiness from sunrise to
sunset may be estimated with considerable accuracy by noting the
degree of cloudiness, on the scale given, as near sunrise as possible,
between noon and 1 p. m., and near sunset ; add these and divide this
sum by 3 ; the quotient will be considered the average cloudiness.

When light fog, light haze, or light smoke has prevailed during the
greater part of the day, with three-tenths or less of clouds, its char-
acter should be recorded as "clear," but when dense fog, dense haze
or dense smoke has prevailed the character of the day should be
recorded as "foggy," "hazy," or "smoky," as the case may be. When
the last-named conditions prevail, it is recommended that observers
note in the column headed "Miscellaneous phenomena" the duration
of same, e. g., "dense fog from early morning till 3 p. m.," etc.

mSTHUCTIONS FOR COOPERS ~,ve OBSERVERS

60. If no rain, snow, or hail has if
make an entry 0.00 in the proper col"
to measure, make the entry "Trace"

MISCELLANE-

used by the public

^y are used by r

clone" and ''

61. Frost. — Occurrence of fii ' " ^ . .

should be specially noted. ' ■ ■ ,-, „ -^

The terms descriptive oi^ ' -_ \
Light, to indicate a frr ' -. ■ i

tender plants and vines .. ' f

to indicate a frost that

the deposit of frost ' ' ■ ' .r clone" to mea

point, ahhough the _i.ate latitudes that is

generally destroye pressure over an extensive area,

destructive of ve? ,^ with which is associated a system

.ally strong, winds that (in the Northern
.ally inward in a counterclockwise direction
commonly accompanied by more or less wide-
iuid precipitation, and constitutes the ordinary,
rnin- or snowstorm of temperate latitudes. A num-
lalions usually move across the United States each
from westerly toward easterly directions, and rc-
nore to pass over a given place.

storms of the tropics, such as the West Indian hurri-
as tropical cyclones, to distinguish them from the
of the temperate regions ; they are smaller in diam-
more violent than the extra-tropical cyclones.
the tornado, or, indeed, any violent and destructive
led a cyclone; but this usage is not accepted among
id is not practiced by the Weather Bureau.
lane is characterized by relatively high barometric
extensive area, with winds that in the Northern
ilate spirally outward in a clockwise direction about
commonly, though not always, accompanied by fair
her; the winds may be very strong over a narrow
belt around the outer part, but tliroughout most of the anticyclone
they are gentle.

75. The terms "high" and "low" refer to areas in which barometric
pressure is above or below that of the surrounding country, without
reference to any noimal values and without implying any specific
peculiarity as to winds or weather.

' mSTRUCTIOTSIS Toa

III. EARTHQUAKES A
NONINSTRl

IMFORTAN

•ally destru
■ the cou

to pr ^ : _

■f . -' ;

: - . ■ 50

• • . I

• - 12

" - . 13, 14, 15, 30

,,ted b; , IC 17, 18, 18

rs, but no plact^ "• ''^

.V. Hence, seismology, v
^,iieiiomena, is of some importa.,
.portance to many. Thus, to be specih^
strictly to the obviously and eminently praci.
the exact locations of those numerous breaks and \i
in the earth's crust along which abrupt slipping a
cause of nearly all earthquakes) most frequently c
far as possible we may avoid them in the location of
structures as dams, irrigation channels, aqueducts, b
ordinary houses.

WHY THE WEATHEH BUBEAtT SHOnLD COU^ECTT EART

78. In spite of the good it clearly would serve, tl
no map of any country that gives at all fully the lo
quake breaks or faults, nor is the collection of the i
the construction of such a map of any extensive
except through the long and constant cooperation of
of observers widely scattered over the area in questic

79. If then the people of the United States are to I
such practical maps as would enable them to reduo
their fears of and losses from earthquake disasters, tl
obviously may most easily be collected by the Weath

it alone, of the various Federal scientific institutions, already has the
adequate personnel and necessary organization.

REQDESTS FOR COOPERATIVE OBSERA'EBS

80. Although each of the Weather Bureau's regular firs^order
stations, approximately 300, will report all earthquakes felt, yet the
territory covered is so great that its seismic disturbances cannot ade-
quately be recorded without the aid of a large number of voluntary
assistants. Hence it is earnestly hoped that, so far as possible, all the

28 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

Bureau's numerous cooperative observers will assist also in the
collection of seismological data, by reporting, on forms (No. 50OO)
that will be furnished for that purpose, the date, etc., of each earth-
quake that they may experience. To each observer the labor will be
exceedingly light, and the time consumed only a few minutes in a
whole year, but the collected results will be permanent and extremely
valuable — absolutely essential to the construction of the maps in
question and exceedingly helpful in the explanation of many obscure
earthquake phenomena. The data thus secured is finally analyzed
by the United States Coast and Geodetic Survey.

INSTRUCTIONS FOR THE COIXECTION OF EARTHQUAKE DATA

81. The particular earthquake data desired are indicated on the
forms that will be supplied to all who take part in this work, but the
method of collecting and forwarding this information to the Central
Office for classification and study is explained by the following
instructions-:

(1) Regular Weather Bureau stations will be communicated with
directly from the Central Office; cooperative stations entirely by, or
when necessary, through section centers.

(2) All routine communications on seismology directed to the Cen-
tral Office will be enclosed in penalty envelopes marked "Earthquake
Reports."

(3) Each regular Weather Bureau station and each cooperative
station that agrees to assist in this work will be furnished with a
supply of forms.

(4) Each station, regular and assisting cooperative, will promptly
fill out and forward in a penalty envelope one form for each earthquake
felt.

(5) The regular stations at Boston, Atlanta, St. Louis, Denver,
and San Francisco will also send to the Central Office such newspaper
clippings in regard to earthquakes in the United States as may come
to their notice.

(6) Each section center may supply forms to other reliable persons
in addition to the cooperative observers. This is especially desirable
in those portions of the country which are either subject to earthquake
shocks or sparsely inhabited.

(7) An earthquake that produces any appreciable damage will be
made the subject of a special investigation determined upon at the
time.

(8) All forms collected by section centers recording the occurrence
of an earthquake will be promptly forwarded to the Central Office.

INDEX

Address of station 50

Air, temperature of 1

Alcohol, in minimum thermometers 12

column detached 13, 14, 15, 30

reuniting column IC, 17, 18, 19

Anticyclone 74, 75

Auroras 48, 66

Black pigment for thermometers 45

Boxes, for shipping thermometers ^ 44

Box support, for rain gage 35

Broken instruments, returning of 44, 47

Bubbles in minimum thermometers 30

prevented by hanging up 21

reuniting column 16, 17, 18, 19

Carbon sheets for making records 50

Catch of rain gage 32

Climate, general phenomena of 67

Clippings, newspapers, of earthquakes 81

Constriction in maximum thermometers 9

Cooperative observer's meteorological record 48

Coronas 48, 62

Correcting mistakes in meteorological record 50

Communication with cooperative observers, conducting 81

Communications on seismology with central office, addressing 81

Clouds 68

Cyclones 69, 71, 72, 73

Daily meteorological observations 48

Day, character of 68

Data comprising meteorological observations 48

earthquake observations 81

Defective maximum thermometers, "retreaters" 10

minimum thermometers, broken alcohol columns 13, 14, 15, 30

reuniting alcohol columns 16, 17, 18, 19

Diameter of rain-gage receiver 34

tube 34

Discrepancies in readings of thermometers 53

Duties of making earthquake observations 80

Earthquake data 76 to 81

from outside sources 81

Earthquake districts, location of 77, 78, 79

Earthquakes, importance of cooperative observations 80

intensity of 76

of appreciable damage 81

Erroneous temperatures, guarding against 11

30 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

Exposure of rain gage 3, 31

instrument shelter 3, 7

thermometers 2, 7

Fog 67

Form 1009 Metl. (Observer's record) 49

Forms for reporting earthquakes 80, 81

forwarding to Central Office 81

Frost 48,61

light 61

heavy 61

killing 61

Funnel of rain gage 34

Gage, rain, catch of 32

description of 34

distance from shelter 3

exposure of 31

size of 34

snow, description of 34

Graduation marks, renewal of, on thermometers 45

Hail 65

Halos 63

Haze 68

"High" 75

Hurricane 72

Index of minimum thermometers 12

reading of 29

sticking of 13

Instruments, broken, returning of 44, 47

Ivory black, use of, on thermometers 45

Keys for shelter locks 6

Legs or support for instrument shelter 4

Location of shelters 7

Location of station, change in 50

Locks for shelters 6

"Low" 75

Lightning 64, 65

Map of earthquake districts 78, 79, 80

Marks, graduation, renewal of, on thermometers 45

Maximum thermometer 9

care in reading 11

description of 9

mounting 28

supports for 22, 25

reading of 26

"retreaters" 10

setting of 24, 52

temperature 48

reading of 51

Mean temperature 49

determining of, from plus and minus 54

Measuring rainfall, units of 36

Mercury in maximum thermometer 9

Meteorological definitions , 69-75

INSTRUCTIONS FOR COOPERATIVE OBSERVERS 31

Meteorological record 50

Minimum thermometer 12

alcohol, column of 12

detached 13, 14, 15, 30

hanging up 21

index of 12

sticking 13

mounting 23, 27

reuniting columns of 16, 17, 18, 19

reading of 29

setting of 21, 28, 52

temperature of 48

reading 51

testing 21

Minus and plus temperature signs 54

mean of 53

Mistakes made in record 50

Mock suns 63

Mounting thermometers 23, 24, 27

Name of station, change in 50

Newspaper clippings of earthquakes 81

Overflow of rain gage 34

Observations desired 48

of earthquakes 80, 81

time of making 49

Packing thermometers 44

"Parhelia or Paraselenae" 63

Phenomena of climate 67

miscellaneous 68

Pigment, black, for thermometers 45

Plus and minus temperature signs 54

mean of 54

Post-ofllce address 50

Precipitation. (See Rain and snow.)

Processes of reuniting broken alcohol columns 16, 17, 18, 19

Rainfall, absence of, recorded 50, 60

catch of 32

measuring of 33, 34, 37, 38, 39

overflow of 34

record of 56

units of measurements 36

Rain gage, catch of 32, 33

description of 34

distance from shelter 3

exposure of 31

size of 34

Reading maximum thermometer 11, 26

minimum thermometer 29

Thermometers, use of plus and minus signs 54

discrepancies in 53

Receiver of rain gage., 34

Record of meteorological observations 48

Reports, preparation of 50

32 INSTRUCTIONS FOR COOPERATIVE OBSERVERS

**Retreaters" lO

Roof exposure of rain gage 31

Seismology. {See EJarthquakes) 76-81

"Setting" maximum thermometer 24,52

minimum thermometer 21,28,52

thermometers, test of correctness 52

Shelter, Instrument S

exposure of 7

height above ground 7

installation of 4

legs or support of 4

locking of 55

locks for 6

Smoke 68

Snowfall, measuring of 40, 41, 42, 43, 57, 58„ 59, 60

record of 57

units of measurement , 57

Snow gage 34

Solar corona 62

Station, location of, change in 50

name of, change in 50

Stationery, for making records 50

Stick, measuring, for rainfall 36

Supports, box, for rain gage 35

steel for rain gage 35

maximum and minimum thermometers 3,25

shelter, wooden 4

steel 5

Temperature of free air 1, 7

erroneous, guarding against 11

maximum 48

reading of 26

mean 49

when plus and minus 64

minimum 48

reading of 29

Testing minimum thermometers for defects 21

Thermometers, exposure of 2, 7

broken, returning of 44, 47

maximum. {See Maximum thermometer.)
minimum. {See Minimum thermometer.)

packing of 44

setting of 21, 24, 28, 52

test of correctness 53

time of 52

shelter for 3, 7

shipment of 44

Thunderstorms 48, 64

Time of making observations 49

Tornadoes 48, 65, 70

**Townsend" thermometer supports, mounting of 22

oiling of 25

**Trace" of rainfall 60

INSTRUCTIONS FOR COOPERATR^E OBSERVERS 33

Tube, measuring, of rain gage 34

diameter of 34

Water, measuring of, in rain gage 36, 37, 38, 39

Weather, state of 48

Whirling (setting) maximum thermometer 24

Wind, disturbing effect on rain gage 31, 33

intensity of, in tornadoes 65

Zero temperature reading 54

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