19 
No. 18, 1.9. A temperature of space about two hundred and 
forty degrees below the zero of Fahrenheit is the basis of all 
his calculations. 
In these calculations there are several serious defects, 
which disprove the conclusion, and require us to look further 
for an adequate explanation of the general prevalence of cold 
in the northern hemisphere during the Drift or Glacial period. 
The amount of the excentricity, the law of radiation, the 
proper point of the orbit for estimating the balance of solar 
heat, and loss by radiation, the law of midsummer heat, 
and the effect of aerial and oceanic currents, are all of 
them elements which seem to me to have been incorrectly 
assumed or left out of view. The combined result of the cor- 
rections thus required will be practically to set aside the whole 
theory. 
32. First, the excentricity is calculated by M. Leverrier’s 
formulae. It might seem beforehand very doubtful whether 
these can be relied on for a date three millions of years ago, 
or even for 850,000, or 210,000 years. But there is here a 
special reason for distrust. The present excentricity is 
•0167836 (Hersch. Ast.), and those at the two eras in debate, 
*0747 and ’0575. Now the maximum for the earth, accord- 
ing to Lagrange, is '07641, and according to Leverrier 
•077747, and the value at 850,000 years ago is thus very 
near the limit. But these calculations were made before the 
discovery of Neptune. Fresh calculations have been made 
by Mr. Stockwell, since that discovery, and the corrected 
maxima for the planets from Venus to Saturn are all 
diminished. Those of Leverrier are M. *225646, V. '086716, 
E. -077747, M. -142243, J. -061548, S. -084919, U. -064666. 
But the later values are M. *2317185, V. *0706329, E. -0693888, 
M. -139655, J. -0608274, S. -0843289, U. *0779652, 
N. *0145066. Thus the value accepted by Mr. Croll for his 
earlier date is one which exceeds the corrected maximum 
by *0053, or nearly a million miles. If Mr. StockwelFs cal- 
culation is correct, it is an impossible value. 
An exact correction would, of course, involve a prodigious 
amount of fresh labour ; but a reasonable approach to it 
may be gained by diminishing the excess over the present 
excentricity in the ratio of the excesses of the two maxima. 
These are *0609634 and *0526052. The values *0747 and 
*0575 will thus become *06676 and *05192, or about nine- 
tenths of those on which the actual calculation has been 
based. This first correction will lessen the decrease of mid* 
winter temperature three or four degrees. 
33. But the method of deducing the midwinter heat from 
c 2 
