454 MONTHLY WEATHER REVIEW. OCTOBER, 1901
Natwe. Londoa. Vol. 64.
Shaw, W. N. The London Fog Inquiry. Pp. 649450.
-Ocean Circulation. PD. 66k-666.
Alpine Journal. New Tork. I'OZ 30.
Mountaineering. Pp 3584393.
Phydeal Rsoho. hncaeter. Vol. 13.
tion. Pp. 903-333.
Fmtiish Gmg9.nphimCl Mngnzino. Ediiibwgh. J W . 17.
Hepburg; Malcolm L. The Influence of High Altitudes in
Pender, Harold. On t h e Magnetic Effect of Electrical Convec-
Bruce, W. S. The Scottish Antarctic E x edition. Pp. 561-569.
Ravenstein, E. e.,. Mill, H. R., and &kaon, H. N. The
Chibas, Eduardo J. A heavy Rainfall at Guuntanamo, Cuba.
S., J. F. Papillons et trmpCratnrc. P. 331.
Otto, Manus. L'Cclnir en boule. Pp. 361362.
Lannelongue, Achard et <)aillard. De I'influence des varia- tions d e tempCrature sur l'bvolution de la tuberculose espCri- mentale. P . 577 559.
Sagnac, G. kode-de production d e rayons lumineus divergents h 180O d u Boleil.
-La station mCtCorologique d e la Tour Eiffel. Pp. 385-304.
-Observations diverses sur les aurores polaires a t 1'6lectricitB
La pluie dans 1'Inde e t les variations d e la tempCrnture solaire.
- Hypromhtres I branche d'Cpicka. Pp. 406407.
- GrEle remarqunble. P. 408. Prine, W. De I'influence des courants de convection Bur les indi- cations d'instruments trPs mobiles. Pp. 409-4%.
-La pliisgrande hauteur atteinte par un ballon month. Pp. 420-
431.
Climatology of Africa. Pp. 582-595.
P. 368.
Bnqinem'ng A-MF~. Neio I'ork. I'd. 46.
La Nature. Pa&. %e dnwde.
Compte8 Rendua de l'Aoid&i& dm Science8. Park. Tome 133.
Pp. iO3-704.
Ciel e l Tme. BriixeUe8. 22ma annle. 1901.
atmospbrique. Pp. 4R?404.
Pp. 405-406.
Da8 W&&. Berlin. 18 Jahrg. Klengel, Friedrich. Ueber das Wetterschiessgebiet bei Win- disch-Feistritz im siidlichen Steiermark. Pn. 2li-326.
Stade, Hermann. Die meteorologische Ho'chstation Zugspitze.
Memardue, W. Die Tempersturverhiltnisse im August 1!)01
Gam. Ltipaig. 37 Jahyg.
Natum'aat?nar.?uafllic?~e Rrcndachnu. Braunachw~g. 16 J ~L T ~.
Pp. 226-339.
unter etwa5O0 N. Br. P. 232.
Potinecke, -. Die Theorie des Regenbogens. Pp. 233-?40.
- Hiihenbestimmung des Nordli'cbts. P. 757.
-Die Regentrge vom 13 bis 16 September.
Jansson, Martin. Ueber die Wiirmeleitungsfiihigkeitcles Schnees.
Pp. 757-755.
P 510 -. "&".
Hann, Julius. Einige Ergebnisse der Teniperaturbeobnclitungeii
Fiteau, August. Temyeratur in den hiichsten Luftschichten.
Fiteau, August. Atmosphire Wirmestrahlung. Pp. 591-593.
Fiteau, August. Staubfall und Gletacherforschuug. Pp. 591-
Cremieu, -. RCpCtition ezpbriences de M. Rowland, relatives h
Margules, M. Uber den Arbeitswert einer Luftdruckverteilung
Zahm, A. F. Luft.widerstand bei Gesrlisindigkeiten unter tsu-
Reichel, W. Luftwiderstand bei elektrischen Sch nellbal~nen.
auf dem Strassburger Miinsterthuni.
P. 591.
592.
Pp. 537438.
Qeographischs Zeitsc?&Tifl. Leipig. 17 Juhrg.
Anmk8 de C h i d e et & Phy8ique. Paria. 7m.a sdrim. Tome 24.
Beiblatter eu den Aimden der P?~g8ik. Leipig. Bmd 25.
la " convection Clectrique."
unci iiber die Erhaltiing der Druckunterscliiede. P. SOS.
send Fuss i n der Sekunde.
Pp. 39-220.
Pp. 8954399.
Pp. 900-901.
Mac Adie, A. Brechung von Schallwellen a n Nebelflichen. P. 901.
Boernstein, R. Das Wetterschiessen. Pp. 940-941.
Memoria8 y Reirislo de lo Socisdad Cientifia " Aiiimw Akatt," Mezico. Tom0 16. Munoz, Jose M. Garcia. h u d e sur l a MBtCorologie agricole du District d e LBon dans ses rapports avec les cultures routinitares e t perfectionnCes. P p 5-24.
Boletin del Inaiiiuto Fi.4ico-Gwgiw$co de Co& Ricia. &in Joat3 de C h ?4 Rita. Air0 1. Pittier, Enrique. La, presiim atmpsfCrica en Snn Jose segiin las observaciones practicadas de lSS9 it 1900 en el Observatorio Mete- orol15gico Nacional. Pp. 39-22.
erts. Pp. 433-439.
&t 0 0 r 0 b ~h s Zeilschr~t. Tien. Bund 18. Bezold, W. v. Die Meteorologie um die Wcntle des Jahrhund-
____~_________________ ~
Hergesell, H. Die Berliner wissenschaftlichen Luftfahrten. Pp. 43949. Ereherzog Leopold Ferdinand. Selten schiiner Regenbogen. Pp. 459460. Erzherzog Leopold Ferdinand. Zum Kapitel der Staubregen. PI,. 460.
- Charles Meldrum. P. 460.
- Vorliiufiger Bericht iiber die internationale Ballonfahrt vom 4 Juli, 1901. Pp. 460461.
-Vorliiufiper Bericht iiber die internationale Ballonfahrt vom 1 August, 1901. Pp. 4til-W.
- Nachtrag zum Stauhfall vom Mjirz 1901. P. 462.
Richter, E. Der Staubfall VcJm 11 MPrz und die Gletscherfor- schung. P. 463.
Becke, F. Nachtrag ziir mikroskopischen Untersuchung des Stanbfalles vom 11 MBrz 1901. Pp. 462463.
Barac, M. Mittheilung iiher den mit dem Regen i n der Nacht
voni 10 auf den 11 Miirz 1901 in Fiome gefallenen Staub. Pp. 463164.
- Meteorologische Beobach tungen in Deutsch-Neu-Guinea. Pp. 463467.
- Regenfall am Kamerun Pi k. P. 467.
MacDowall, Alex. B. Mond und Repenfall. P. 469.
MacDowall, Alex. B. Mond nnd Wetter. Pp. 408169.
Forfeitt, William. Regenmessungen LLI Upoto am oberen Kongo
-Die Bedeutung des Wasserrlampfes und der Kohlensiure bei
- Gleichzeitige Beobachtungen auf dem Xtna-Observatorium.
- Sonnenreflektor. P. 473.
-- Frank Very iiber seine Experimen~luntersuchen iiber atmos-
Schwzdbe, G. Mittelwerthe der Temperatur fiir Berlin (Aussen-
- Meteorolopische Beobachtungen zii Norway-House, Hudsons-
- Direkte Erseugnnp der S-Strahlen in der Luft. P. 476.
Wolfer, A. Provisorische Sonnenflecken-Relativzahlen f i r das
1899-1900. P. 469.
der Absorption in der Atmosplliire. Pp. 450-471.
Pp. 4 i l 4 i 2 .
phiirische Stralilung. Pp. 4 i 2 4 i S .
staclt), rediicirt auf die Periode 1851-1900.
bailiinder. P. 475.
111 Quartal 1901. P. 476.
Pp. 473-175.
PHE MEASUREMENT OF SUNSHINE AND THE PRELIMI-
NARY EXAMINATION OF ANGSTROMS PYRHELI-
OMETER.
While the writer wa8 in attendance last August at the con-
rention of Weather Bureau officials held i n Milwaukee he
vas plied with iiiinierous questions pertaining to the instru-
mental work of the Weather Bureau, ninny of which related
;o the measurement and registration of sunshine, especially
n varying degrees of intensity. The sunshine recorders' a t
>resent in use a t Weather Bureau stations are recognized as
tt best but imperfect, and the records only approximate and
ncomplete.
The urgent need of decidedly improved apparatus for this
purpose is keenly appreciated by many of our officials whose
:lose daily relation with agricultural interests emphasizes
;he incomplete character of the data at present available.
rhe subject is one, however, which is but imperfectly under-
3tood by the majority of those who discussed the question
uith me, and it ~eenis appropriate, therefore, a t this oppor-
,unity to preface the present account of the comparison of
)yrhelionieters with a few brief statements of the general
>rinciples underlying nieasurements of solar radiation.
The present state of our knowledge of this intricate and
leeply involved problem has just been summarized by Mr. Frank W. Very' in an excellent article which is recommended
.o everyone studying this question. This writer, however, aB
iecessi ty compells in so condensed a summary, presupposes
t reasonable acquaintance with the subject on the part of his
*eadem, whereas, i t is desired in what follows, to set forth
iriefly such elementary facts and principles as will help the
'Annual Report of t h e Chief of t h e Weather Bureau. 1891-93, p. 30; innual Report of the Chief of t h e Weather Bureau, 1893, p. IS. MONTIILS WEATHER REVIEW, August, 1901,
C. F. MARVIN. Profeseor In charge Instrument Dhlslou.
~
The Solar Constant.
1. 357.
OCTOBER, 1901. MONTHLY WEATHER REVIEW. 465
~
less fully informed reader to more perfectly comprehend thc
whole subject. The solar energy which, when received a t the surface of tht
earth, produces all our optical, thermal, electric, and cheniica
phenomena, obviously must first traverse the envelope of at.
mosphere surrounding the earth. This atmosphere even wher
in the clearest condition absorbs or intercepts a t least a smal
part, aud, under less favorable conditions, a very considera.
ble part of the energy which arrives at its extreme outei limits. Measurements therefore of solar radiation niade i u
the lower regions of the atmosphere necessitate also a study
of the absorption by the atmosphere. The absorptiou of thc
radiant solar euergy by gases and vapors and its disper~ion
and diffusion by dust and other minute constituents of thc
atmosphere are exceedingly complex phenomena, and are, in
fact, a t the best but partly understood or measured quanti.
tively at the present time.
It is well known that ordinary white sunlight is made
up of all the colors of the rainbow. ,It ig, perhaps, lese generally known that this so-called " visible spectrum )' ie
but a small part of the whole solar spectrum, portions of
which, invisible to the human eye, exteud beyond the violet
and especially far below the red. All these successive por-
tions correspond, respectively, to radiant solar energy of dif-
ferent wave lengths. Some of the waves traverse the atmos-
phere with almost perfect facility, whereas others are in part,
and some almost wholly, suppressed or absorbed and dis-
persed ; and no study of atmospheric absorption can be com-
plete without a full aualysis of the " selective absorption of the waves of different length by the air and its constitu-
ents. It is plain to be seeu that this task is both complex
and difficult to accomplish in a highly satisfactory manner. For agricul tural purposes, however, the heat effect actually
produced a t the surface of the earth is the desideratum, and we need very much an instrument that will measure and reg-
ister this hour by hour and day by day, much the same, for
example, as we nom nieasure the movement of the mind hour
after hour, or the amount of precipitation season after season. Impressed with the visible heating power of the sun as
shown by its effects 011 thermometers and articles generally
esposed to its direct iiifluence, alniost every one seeking to measure this radiant energy is apt to set out with a ther-
mometer, especially one with a blackened bulb, the inclica-
tions of which are considered to nieasure in degrees the in-
tensity of solar radiation. This is a serious mistake, but i t is embraced so geuerally that it can not be too strongly con-
demned. I do not mean to imply that observations of tem- perature in the sunshine can not be used to measure solar
radiation, but for this purpose secondary observrttions of
other conditions are equally important, and, a t the best,
many difficulties are encountered. The whole matter will, I
think, be much better understood by a concrete illustration.
Suppose I desire to measure the rainfall during a storm.
but that I have for this purpose a rain gage such as indicated
in Fig. 1. We will suppose this vessel is made of glass, so that the contents within may be seen from the outside, and
that the slender stem is graduated. The point a t which this
gage differs esseutially from an ordinary gage is that the
bottom has a hole in i t a t -4. Furthermore, I am obliged to
use this gage with the bottom open. I expose it so that the rain falls into it freely, and I will assume that the hole in
the bottom is not so large but that even with a slow rainfall
at least a small quantity of water will stand iu the tube a t
the bottom. Now, what shall we find with such a gage as this ?
If. the rain falls continuously, i t will be seeu that the water
rises in the graduated tube and stands steadily at a certain
point, such that the water runs out of the hole in the bottom
just as fast as it flows in a t the top. If the rain falls more
rapidly, the water will stand a t a higher point in the tube,
61-2
but it will also run out at the bottom more rapidly. Ob- viously, it will stand lower aud run out more slowly when
the rain falls less rapidly, etc. We might experiment with this gage by dropping or pouring water into it until the
column attained a certain height, then, suddenly cutting off
the inflow, we could note the exact time re- quired for, say, a cubic inch of wa.ter to run
out a t the bottom. From a series of .experi- ments like this, with suitable variations, we
could develop a t least two important laws of
action of the gage, namely: first, that the rate
of outflow differs noticeably for each height of
the column ; secoud, that for a given height of
the column the rate of outflow is sensibly the
same every time the experiment is repeated.
Finally, the quantity of outflow, and hence of
iuflow, corresponding to each poiut of the
graduated scale would be established. Such a gage can, it is true, be used for measuring rain-
fall, hut everyone will admit it is far from 8
convenient or satisfactory instrunient for this
purpose. Bad as if is, however, i t is better for measuring precipitation than is a thermometer
placed in sunshine for nieasuring solar radiation.
The trouble in both these instruments is that the water in the one case and the heat in the other escapes as fast as it is
received. Wheu the column of the thermometer is stationary
it loses heat just as fast as i t receives it, but, unlike the rain gage, which, ps we have seen, loses and receives water always
at the same rate for a given indication of the column, the
heat lost and received by the thermometer has practically no defiuite relation to the height of the column of mercury; in
Fact, we are oldiged to measure the loss in some way for each
particular case. In the rain gage the water is received only
ttt the top and lost only at the bottom; the thermometer,
however, receives and loses heat in a great variety of ways.
Heat is exchanged, for example, by radiation to and from
wery surrounding object ; by convection currents in the air,
3r by the wind; by conduction along the stem, eto. It is
plain to be seen that all these circumstances greatly compli- :ate the use of thermometers in all such measurements as we
[low have under consideration.
The point we want to emphasize and present in a forcible
manner in this illustration of the rain gage is that in the case
If the thermometer there is an irregular outflow of heat, as
well as au inflow, that must be looked after and carefully in-
:luded in all considerations. Those who have but partly
itudied the subject often direct attention quite wholly to the
nflow, or they virtually assume that the outflow is an inva-
:iable oue, and hence are led to erroueous conclusions.
It is not the purpose of the present paper to describe the
relatively complicated processes that have been developed by rhich to measure solar radiation, but it is plain that any
tpparatus which registers only variations in the temperature
.ndicated by a thermometer exposed directly to sunshiue fails
;o give any useful record of solar radiation, unless the irreg-
ilar exchange of heat with the surroundings is fully con-
;rolled or compensated. A little thoughtful consideratiou of the fact that we are
ictnally dealing with an outflow, as well as an inflow of heat
n this problem leads us at once to the next important con-
lideration, namely, that units of temperature are not suitable
inits in which to measure solar radiation. We measure water
n pounds, or gallons, or cubic feet. We measure heat in
;herma1 units, or calories. With possible rare exceptions the
netric units are uow the only ones employed in measures of
iolar radiation, and in this case the unit is the calorie, that
s, the quautity of heat required to raise one gram of water
L o iu temperature ou the centigrade scale. This quantity of
FIQ. 1.
456 MONTHLY WEATHER REVIEW. OCTOBER, 1901
heat is also often called the gram-calorie, in order to distin-
guish it from a much larger quantity of heat, also unfortu-
nately called a calorie, namely, the quantity of heat required
to raise the temperature of a kilogram of water lo centigrade.
The foregoing considerations indicate the lines along which
improvement in instruments for measuring and recording sun-
shine must be worked out. Many valuable suggestions will
be found in a report by Violle in the Proceedings of the Inter-
national Meteorological Committee, St. Petersburg meeting,
1898.
Solar conatant.-Having outlined in whit precedes the
fundamental principles which must guide us in studies of
solar radiation, we will: state briefly the ' general numerical
results of the most satisfactory measurements thereof and the value of the solar constant deduced thereby.
The intensity of the solar radiation, received and measured
a t the surface of the earth, varies greatly depending upon
the condition of the atmosphere and the thickness of the
layer of air traversed by the solar rays as modified by the
latitude of the place, the hour of the day, the season, the alti-
tude, or the barometric pressure, etc. Under the most favor-
able conditions when the sun is in the zenith it may attain to
almost 3 gram-calories per square centimeter per minute. That is to say, if all the solar heat which falls on a square
centimeter of surface, normally exposed to the sun is ex-
pended in warming water, the heat will increase the tempera-
ture of almost 3 grams of the water lo centigrade in each
minute of time. Ordinarily, however, owing to the intercep- tion by the atmosphere of considerable portions of the heat
the value is much less than three calories. Taking the maximum readings of solar radiation that may
be obtained from time to time and applying such corrections
to each as shall compensate for the loss of heat in transit through the atmosphere a t the time, we obtain the so-called
'' solar constant," that is to say, the heat received from the
sun a t a point just outside om atmosphere. To be strictly
accurate this value must be reduced to one corresponding to a
definite distance from the sun, as the distance of the earth
from the sun undergoes certain well known annual changes.
From the best data now available on this subject, it seems
that the solar constant, as defined above, is about 3.1 gram-
calories per square centimeter per minute.
The Weather Bureau has recently undertaken a series of
special studies of the whole question as to the value of the
iolar constant and its variations, if any, with time, and the
remainder of this paper will be dewted to a brief description
of the preliminary tests and intercomparisons of the Ang-
strom electric compensation pyrheliometers to be employed
in this work. The apparatus is designed primarily with a view to easy
portability and its use in the field, on mountain tops, and in
places remote from the usual facilities of installation. The pyrheliometer with all its accessories, mounted on a slender
tripod, is shown in Plate I. The total weight, packed in the
carrying case is 19+ pounds.
The pyrheliometer proper is within the tube, AB. The gal- vanometer and telescope, by mea36 of Fvhich temperature
adjustments are effected, as will be more fully explained
hereafter, are suspended a t C. D is a small .slide wire rheo-
stat. H is an ammeter with which the strength of the elec-
tric current is measured. The carrying case with a single cell of Leclanche battery is seen below. The mechanism of the pyrheliometer is shown in the upper
left-hand corner of Plate I, and occupies about one-half the
length of the tube, AB. A and B are two very thin bands
of platinum foil, about 1.5 millimeters wide and 20 millime-
ters long. The back of each band is coated with a thin layer
of silk insulating paper, and cemented against this is a thin
.
strip of copper foil, very similar to the platinum bands
themselves. Finally, the middle points of the copper strips
are joined to each other by a small inverted n-shaped piece of constantan' wire. A portion of this wire is plainly
seen a t c c. The ends are hammered down thin near the
junction with the copper bands. The several parts are so mounted that the copper bands are in electrical connection
with the small lateral rods terminating a t T and T, respect-
ively. The opposite ends of these rods terminate in binding
screws, one of which %an be partly seen a t E. Both pla-
tinum bands are joined a t the lower end to the terminal, F,
and a t the top end conuect respectively to the terminals,
and G L is the top end of a switch lever. In the position
shown the electrical circuit is closed through G and the pla-
tinum strip, A. When the switch is thrown to the right the
circuit is opened through A , and closed through G and
the band, B. The platinum bands are carefully coated with
lampblack.
The pyrheliometer tube, AB, is closed a t the upper end
with a cap having two slits or openings. A small double
shutter is pivoted back of this cap in such a manner that
one or the other of the two openings can be closed by the '
shutter, or the shutter may be given a middle position in which both slits are open. A series of diaphragms with rect-
angular apertures, successively smaller, occupy the space in
the tube between thecap and shutter and the platinum bands. These serve to intercept stray radiation and limit the expo-
Ewe to the rectangular aperture across which the platinum
bands, A and B, are stretched. A small thermometer, t, indi-
cates, approximately, the temperature within the tube, AB. The action of the iiistrument involves the use of two dis- tinct and separate electrical currents. The one is thg thermo-
electric current produced by the constantan-copper thermo-
electric junctions, c, c, on the back of the platinum strips. This current flows through the galvanometer and is generated
only when there is a difference in temperature between the
two bands, A arid B. The other current is furniehed by a
cell of Leclanche battery, or equivalent. This current is controlled and its strength regulated by means of the rheo-
stat, D, and then passes through one or the other of the bands,
A or B, as determined by the position of the switch, L, thence
through the ammeter, H, where the strength of the current is
indicated.
The apparatus is set up so that the tube, AB, pointsdirectly toward the sun, as determined by means of suitable sights
for that purpose. The shutter is first set so that both bands
are exposed to the suu and are therefore equally heated. The
needle of the galvanometer, G, is then adjusted, if necessary,
EO that the middle portion of the galvanometer scale, S, ap-
pears plainly in the field of view.
It is assumed the bands, A and B, are equally heated by the
sun, as they must be, seeing that they are as similar as pos- sible and are otherwise equally circumstanced. The thermo-
electric junctions a t c, e, on the back of the bands must, then,
have the same temperature, and therefore no thermoelectric
current flows through the galvanometer. The scale reading,
under these conditions, is the zero position of the galva-
nometer. If now the shutter be turned so as to screen the
band, B, for example, leaving A exposed to the aim, the shaded
band will cool off and the galvanometer will deflect. Now,
let a current from the battery be sent through the shaded band, B; the latter will be heated thereby, and by a suitable
adjustment of the rheostat the galvanometer needle will be
returned to its original zero position. This means that'the shaded band, B, is now heated by the electric current sent into
i t until its temperature is the same as that of the band, A, ex-
posed to the sun. We thus have two bands, themselves equal,
sThis is an alloy which forms a strong thermoelectric couple with copper.
OCTOBER, 1901. MONTHLY WEATHER REVIEW. 467
Ampetss. .00100 .o0400
.aMal .ouBoo .01oOo
both a t the same temperature, both in the same environment both losing and receiving heat a t the same rate; the one
heated by the solar radiation, the other by an electric current,
The amount of heat generated by the electric current is easilg calculated with accuracy when we know its strength and the
resistance of the platinum bands. Thus we are able to meas-
ure the solar radiation in a very satisfactory manner. The following general instructions have been issued for the
guidance of those using the pyrheliometers. The apparatus being completely mounted the full detaile
of a complete observation are about as follows:
1. Start with current off; i. e., rheostat switch on neutral
point. Point tube to sun by aid of sights and set shutter in central position so that the sun heats both strips. . 2. Note and record: a, the temperature of attached ther-
mometer ; b, the time ; e, the zero position of galvanometer.
3. Designating the two strips by the letters A and B; screen B and set switch a t back of tube so that current passes
through B.
4. Cut in current and adjust rheostat, BO that the galva- nometer needle returns as nearly as may be to the zero read-
ing recorded under (2).
5. When the adjustment under (4) is attained read and
record ammeter.
6. Screen A and switch current through it and readjust
rheostat, if necessary, as in (4). 7. Read and record ammeter for No. 6 adjustment.
8. Note sights on tube and readjust pointing of pyrheli-
ometer, i f necessary.
9. With A still screened, readjust rheostat, if necessary, and
restore galvanometer to z0ro.
10. Read and record ammeter.
11. Screen B; switch current through it and restore galva-
nometer to zero.
12. Read and record ammeter.
13. Set shutter in middle; i. e., expose both strips to-the
sun and cut off current a t rheostat.
14. Read and record zero position of galvanometer.
16. Note and record time; also temperature of attached
thermometer.
The following example is given of a set of readings forward
and bapk on pyrheliometer No. 34.
Am rm. Amparas.
.ooase .OM00 .m 1 .m .m -00800 .01000* .009996
.d&O .o[rm
October 29, 1QOl.
M5p.m ..... B O 0.787
Bands exposed. Qram-calories Temperature. - per sq. om.
Centigrade. per minute. BothAand B.1 A. 1 B. 8. --
~
I n computing the results the mean of the two determinations
of current strength should be multiplied by the coefficient taken from Angstrom's table of constants corresponding to
the temperature shown by the reading of the attached ther-
mometer. (See Table 6.) The result is the gram-calories
of heat received from the sun per square centimeter,.per
minute, as observed a t that place and moment of time.
From this the solar constant is to be determined by further
investigations into the absorption by the atmosphere.
The observations may possibly be abridged somewhat with-
out loss of accuracy, and, on the other hand, if difficulty is
found in restoring the galvanometer to zero in a satisfactory manner, it may be necessary to record the reading and estab-
lish a slight correction for the discrepancy.
Before undertaking a direct comparison of the pyrheli-
ometers it was necessary to compare the three Weston
direct reading ammeters used in the measurement of current strength.
For this purpose the three instruments were joined in
A.
--
A:% .Si8
.a .am .400 .988 .So!! .a98
.401
.am .a80
series with a battery and with an adjustable resistance, which
latter was regulated so as to bring the index on ammeter
No. 4321 to a particular division, whereupon an assistant
noted, simultaneously, the readings on the two remaining in-
s truinen ts.
Each instrument has a double scale, one, the upper scale,
from 0 to 500, divided into 100 equal parts; the other, the
lower scale, from 0 to 10, also divided into 100 parts. The
following table gives the readings made :
TAB- l.-cOWlwb?l Of W&?b WWk%%l'8.
Scale readinga Mor upper scale).
B.
*.%I
.a .405
.896 .885 .sea .a07 .a95 .a78
.an7 .am
No.4.321. I No.-. I No.4815.
Amperea. .05Uo
. loo0 .I500
.m .2500 .8ooo .m .4ooo .4500
.m
~
~.
:IT ....... :E. .. ... :a ....... :84 ....... :a8 ....... :42 ....... 1:49 ....... ':JS. ...... !:58 ....... ,c02 .......
Yoale readlngs (for lower scale).
NO. 4821. 1 .NO. W8. 1 NO. 4815.
~
~.
115 .402 .400 18.0 1.14 118 115 .408 .4W 18.6 1.16 84 117 .a98 .8W 17.6 1.15 108
118 A95 408 18.6 1.15 05
le0 .891 .406 18.1 1.12 105 117 A98 .398 18.1 1.18 108 191 .894 .8RIl 17.2 1.08 95
116 ,988 .8K lT.8 1.09 90 119 .W .8[18 17.2 1.04 1.20 116 .BO .886 11.0 1.04 98 -
I I
*And off the scale.
The greatest discordance a t any point seems to be about
1.3 per cent a t 0.160 ampere on No. 4306. Next the pyrheliometers, in pairs, were directly compared
in the sunshine. In the first comparison, October 26, the
readings were not made forward and back, in the manner ex-
plained in the instructions, but were recorded directly in the
xder indicated.
The results are given in full in the accompanying tables.
The column of results headed "calories, etc.," is computed
by the.equation--
in which the value of the constant k is taken from Table 6 For the particular instrument in question, and the corre- iponding temperature recorded for the observation.
TABLE g.-co9nprvriaon Of A?bg&69?&'8 ~h&OmSkW8.
Pyrhdlometer No. 81. Ammeter No. 4321. I Pyrhellomebr No' 84. Ammeter No. 4806.
1 Band exposed to sun. 1 r: 1 8. I Bandexposedtosun.
-
0:
$ c
[
E" -
0
16.1 16.0 16.0 16.0 16.5 16.5 16.0 16.0 16. 5 16.1 16.0
. ....................
-
Q.
4a
-
1 .0 1.10 1.18 1.18 1.11 1.09 1.10 1.15 1.10 1.06 1.05
1.100 -
-
458 MONTHLY WEATHER REVIEW. OCTOBER, 1901
-
A.
Am& .!a96 .899 .808 .m .m .299
.a .Y85
.gel .m .a52
.9@l3
.280
.ma .275
.m .m
.ma
.m
__
TABLE 3.-Compal.Mon of AngatTb’?lb’a pyrllknnetetr.
B.
--
A:& .88Y .a46
.881
.840
.m .8b
.m .886
.810 .a10
.m
.a18
.905
.808 301
.ais .ai0
.an
.ai2
Pyrheliometer No. 88. Ammeter No. 4815.
E B
p 8
!s
91.8
0
91.6
21.6 21.4 21.8 81.9 21.1 21.7 21.1 81.0 91.0 2l.l 01.0 91.5
91.8 21.4 81.9 81.8 ai. 1
91.5
oat. e8, 1Wl. Time, p. m. A%hB.
-~
Gd.wr0 186
1I 188 lee 141 128 145 1% 160 184 149 129 IW
160 142 148 I42 165
184
189
1m. ..... 1:87.. .... 1:40. ..... I:&...... 1:47.. .... 1:I.. .... 1:14. ..... 1:57.. .... 9 M . ..... 9 f i . ..... Om.. .... 298. ..... 8;18. ..... 9%. ..... 8:s.. .... 8$31......
%ad... .. 9m. ... ado. ..... 8:M. .....
L e * #,
h I
0
21.8 21.0 81.0 91.0 21.6 21.9 91.9 91.9 81.9 88.0 91.0
81.7 21.6 81.9 81.9 21.0- 21.0 21.0 91.1 81.0
I
I Band exposed to sim.
Both AandB
.-
Qal.zei-o 117 108 111 8.3 95 89 144 148 158 184 188 165 165
190 188 110 116 157 160 118
A.
-
A;m& .541 .8.W .84S .847 .a44
.841 .881
.a .815 .507 .W ,900 .a30
.818
.m .wwI .a80
.m
.a58
Mean of 10 pairs of
I
B.
Amp. .m .850 .850 .852 341 .a48
.941 .ab 3% .864 .a04 .86l .a 7 .m
.m .m .881 .83a
.a49
.ai8
~
Pyrheliometer No. M. Ammeter No. 4506.
, Band exposed to sun.
.................................
8.
$3
-
?3g __
.M .E64 .855 .E74 .855
.a5 .870 .841
.m .787
.885 .816
.m .m .762 .815 .7s .616 .749
.m
.m -
The constants of the instruments were very carefully de-
termined by &ut Angstrom, and are combined in the follow-
ing table :
TABLE 4.-Conalattla of p~hlwrnei2ra.
I No. 28. I No. 81. I No. 84.
I
Electrioal resibtance of the bands at nOp C. (T) .............. Coetaoieut of variation of resistance with temperature.. .. Width of bands (b ) oentlmeters.. ........................... Absorbing power of the surfaces (a) ................ ........I 0.98
I I
The intensity of radiation is given by the relation
Q=qlQb i’ - cd - 60 gram-calories per min. per cm.’
Or Q =k i ’ . .
( i = intensity of the current in amperes.) The coefficient k has, a t different temperatures, the follow-
ing values:
TABLE 5.
N0.W .......................
No.84 ..................... I 7.121 7.151 7.191 7 .2 2 7.28 7.29 .......................
~
NOTES BY THE EDITOR.
WEATHER BUREAU MEN AS INSTRUCTORS.
Mr. George E. Franklin, Local Forecast Official, Los An-
geles, Cal., hag given instruction to the class in physical geo-
graphy of the Los Angeles High School in the construction and
use of meteorological instrument6 nnd the general work car-
ried on a t stations of the Weather Bureau. For this purpose the class, which numbers about 160, visited the local Weather
Bureau ofice in sections on different days during the latter
part of the month. Similar instruction is to be given to the pupils of other schools during the winter.
Mr. A. E. Hackett, Section Director, Columbia, Mo., has
undertaken the instruction of a class in climatology in the
Missouri State University. The class meets each Friday dur- ing the first semester and a greater portion of the time will be devoted to the study of the more important climatic features
of the various sections of the United States. This course is
now required in the Missouri State University for the degree of Bachelor of Science in Agriculture.
Mr. H. W. Richardson, Local Forecast Official, Duluth,
Minn., report6 that on October 24 he addressed the senior
class of the Convent of the Sacred Heart a t his office,
the topic being the United States Weather Bureau. On October 29, the senior class of young ladies from the Crag-
gencroft Private School, Duluth, Minn., visited the office and
after explaining the various instruments, Mr. Richardson ad-
dreesed them upon Weather Forecasting and the Work of the
United States Weather Bureau.-H. H. h-.
--
-.----
There are many other fields for the application of our knowl-
edge of climatology and one of the most interesting is that
branch of geography called physiography or the study of the
action of the atmosphere in altering the surface features of
the-earth. As many of the readers of the MONTHLY WEATHER RE-
VIEW are teaching geography, climatology, and physiography,
we believe that they will often find oppllrtunity to utilize
ideas drawn from the following outline of the subjects treated
of by Prof. Dr. George B. Shattuck of Johns Hopkins Uni-
versity in his recent c3urse of public lecturee in Baltimore.
GEOGRAPHY OF NORTH AMERICA..
LECTURE I.
SUBJECT.-PHYSIOGRAPHIC FEATURES OF NORTH AB~ERICA.
Relations of mititaetdal plalaaua and owan baains.--Methods of sound- ing: lead line; Sigsbee sounding machine. Contour of ocean bottom: levels; ridges; deeps. Contour of continental plateaus: continental shelf; submarine earthquakes; cable ruptures. Rebtione of North Arnica to ihol7rep. watinenla and to th srcwvunding ocmnbaaim-Atlantic basin; Pacific basin; Arctic basin; Antillian basin. Hypomat.ric fedurea of North d,?t~tic.o.-Atlantic Plain: position; es- tent; characteristics; subdivisions-Coastal Plain, Piedmont Plateau. Appalachian Mountain System: position; extent; characteristics; sub- divisions-Blue Ridge, Appalachian Valley, Cumberland-Allegheny Plateau. Great Central Plain: position; extent; characteristics; sub- divisions-Laurentian Highlands, Mackeiizie River Basin, St. Law- rence Valley, Mississippi Valley, Prairie S t e f p Black Hills, Ozark Mountains, Llano Estacado, Bad Lands. Cord1 eran Mountain System: position; extent; characteristics: subdivisions-Rocky Mountains, Plateau Country, Great Basin, Coast Ranges. Antillian Mountain Sys-
tem: position; extent; characteristics; subdivisions-Greater Antilles, Lesser Antilles, Bahamas, Trinidad-Tobago group, Mountains of Cen- tral America.
LECTURE 11.
APPLIED CLIMATOLOGY.
By practical climatology we ordinarily mean the observ-
inn and recordinn of the weather. the memiration of mean
SUBJECT.-CLIMATOLOGY AND HYDROGRAPHY. va’iues and the afilication of t h i s climhdogical knowledge
to the benefit of mankind. Practical meteorology implies C~vbatolog#.-Definition of climate: precipitation: evaporation; cir-
daily weather map and the study and prediction of 6tornls I heat in atmosphere; ocean currents-horizontal, vertical; mean an-
and changes in the weather.
observations bL1t a different form Of record, “9 the culation; condensation; storms; distribution of Temperature:
I nual temperature; variation in temperature.
XXIX-117. Plate I.
Angstram’s Portable Electrical Compensation Pyrheliometer.