22 S. Newcomb—Some points in Climatology. 
founded, and that, as temperature rises, radiation increases in a 
much higher ra ratio. To speak more exactly, if we take a series. 
of temperatures in arithmetical progression, the corresponding 
rates of radiation of heat will not be in arithmetical progression, 
but in a series of which the differences continually increase. 
An immediate inference from this general law is that if an 
ive 
annum, its mean annual temperature will be a maximum when 
this radiation is oe and will be lower the more irregular 
the reception of hea 
Now it is well ices that the total amount of heat received, 
not only by the earth as a whole, but by each hemisphere, is 
constant, notwithstanding the change i in the earth’s eccentricity, 
but in virtue of the law just stated, any portion of the earth’s 
ted more uniformly. But roll does not, so far as I have 
ever noticed, adduce this ee at all. On the con trary, he 
assumes Newton’s law of radiation proportional to temperature 
under which the cause would not act in the way suggested. 
One great source of in-conclusiveness in Mr. Croll’s results 
seems to me to be a lack of quantitative precision in hi 
guage. Though he may use numbers wherever it seems to him 
they are applicable, one can hardly fail to notice that the quan- 
rina terms he most uses are such as “great,” “very great,” 
mall,” “comparatively small,” and these without any state- 
oer of the units of comparison relatively to which the expres- 
sions are used. Now I deem it not improbable that the differ- 
ence between a cold and a hot epoch may be due to the very 
small preponderance of one or the other of several antagonistic 
causes; and, if so, quantitative precision is necessary to lead to. 
any reliable ‘conclusion. 
shall now enter into some details: Mr. Croll suggests that. 
I may have forgotten the researches of Pouillet and Herschel 
into the temperature of space. I reply that I regard the con- 
Sega that the temperature of space is —239° as having no 
und basis. To speak with greater quantitative exactness, it 
rate precisely the same value as a photometric estimate of the 
intensity of star light, founded on observations of the sky, 
made in full day, with an attempt to eliminate the light re- 
flected by the sky so as to find what residue comes from the” 
stars. The fact is, that no observations of radiant heat from 
stellar spaces at large can be made below the uppermost —_ 
of the earth’s atmosphere, owing to the intervention in 
regions of the radiation from the atmosphere itself. 
r. Croll concludes, using Newton's law of radiation, that 
the heat received from the stars is to that received from th 
