418 
Professor Langley deduced from his bolometer 
studies about 38.00 calories; that Angstrom and 
others obtained 4.00 calories, and those were 
common results for some years. Mr. Abbot re- 
duced the value to 1.94 calories, relying solely 
upon the pyrheliometer, and at the same time 
recognized that the ordinates of the bolometric 
spectrum indicate a solar temperature of about 
7000° A., the pyrheliometer requiring only 
5800° A. He passed over this wide discrep- 
aney by assuming that the sun does not 
radiate as a black body. This is the critical 
point. The Poynting equation of equilibrium 
asserts that the surface flux of radiation over 
a given volume sustains a certain volume 
density whose temperature is 7. This equa- 
tion has been applied by me in detail to the 
earth’s atmosphere, so that in ten distinct 
integrations the volume density from the sea 
level to the vanishing plane amounts to 3.98 
calories; it has been applied in the sun’s at- 
mosphere with the result that the solar radia- 
tion originates in a deep isothermal layer at 
the temperature 7655°. It is, therefore, black 
radiation, of an equivalent value of 5.85 cal- 
ories; using Abbot’s coefficients of trans- 
mission for several spectrum lines, from the 
center to the limb, this is depleted by 1.87 
calories, thus agreeing with the terrestrial 
data and the bolometer. This result destroys 
Abbot’s theory, and renders his pryheliometric 
method useless. 
It is not difficult to understand the source 
of Mr. Abbot’s error. He relies upon the 
Bouquer Formula of depletion, and, indeed, 
substitutes this for the Poynting Theorem, 
which is erroneous. When there is lack of 
equilibrium between the surface flux and the 
volume density, there is a product of free 
heat, dQ—=cdT, while the temperature is 
changing. The pyrheliometer works on this 
change of temperature alone, omits to register 
the stored potentials and inner energy within 
the metals, glass, mercury, these last being 
very difficult to follow. Im short, Abbot’s 
theory identifies the surface flux of radiation 
with this free heat, and it follows that it does 
not manifest the entire radiation received. 
For these reasons I have abandoned Abbot’s 
SCIENCE 
[N. 8. Vou. XLVIII. No. 1243 
methods and substituted those found in my 
“Treatise on the Sun’s Radiation.” It may 
be noted that the pyrheliometer is a very in- 
efficient apparatus for atmospheric studies, be- 
cause it is unable to eliminate the depletions 
due to the effects of vapor, dust and even mo- 
lecular scattering in the higher levels. Apply- 
ing certain correcting ordinates, the stations 
at Cordoba-Pilar, 488 meters, and at La 
Quiaca, 3465 meters, are working together 
within 0.02 calories, and they follow the solar 
variations as indicated by the sun-spots, prom- 
inences, magnetic field and the meteorological 
data in Argentina. It is imperative that Mr. 
Abbot should abandon his unfortunate pyr- 
heliometer method, which is flatly contradicted 
by a very extensive series of data, in favor of 
the results which are clearly indicated by his 
admirable observations with the bolometer. 
Frank H. BicELow 
Sonar AND MAGNETIC OBSERVATORY, 
Pimar, F. C. C. A., ARGENTINA, 
August 7, 1918 
FIREFLIES FLASHING IN UNISON 
To THE Epitor or Scmnce: In Scmnce for 
July 26, 1918, there appears an article on 
“Fireflies Flashing in Unison,” by Edward S. 
Morse. Confirming his statement and that of 
other observers that fireflies do at times syn- 
chronize their flashes I beg to relate an in- 
stance that oceurred on the evening of May 4, 
1918, on the Benguet road. At that time I was 
a passenger on the auto-stage run by the Phil- 
ippine government between the railroad sta- 
tion at Mangaldan and Baguio. As the stage 
rounded one of the numerous curves on the 
grade there appeared on our left, apparently 
in motion, a ghostly incandescence which came 
and went in regularly repeated flashes and in- 
tervals of darkness. The appearance was un- 
canny and was plainly visible to all the pas- 
sengers in the stage. We did not at first realize 
its cause but soon attributed it to fireflies. As 
T have said the light was apparently in motion, 
but I am inclined to believe that the insects 
which caused it were not in continuous flight 
but were congregated (as is frequently the case 
in the Philippines) about some tree standing 
