Ch. XIII.] 



CLIMATAL EFFECTS OF EXCENTEICITY. 



273 



I conceive that, although under 



circumstances the 



greatest 



favourable geographical 

 accumulation of snow would 

 always take place at that pole where midwinter happened to 



> 



occur in aphelion, there must be a continual excess of cold 

 in both hemispheres, so long as the large excentricity lasts 

 throughout all the nhases to which one or 



inoi 



) cycles of 



precession and the revolution of the apsides would give rise. 

 I also think it probable that be the amount of excentricity 



t> 



small 



and sea is not exceptional, or whenever a normal condition of 

 things obtains as expressed in the ideal map, fig. 13, p. 263, be 

 no increase of cold from year to year. Moreover, it appears 

 to me almost certain, that whenever a deep ocean prevailed 

 at both poles, there would be, instead of a storing up of ice 

 in polar regions, no snow whatever on the globe : and during 

 extreme excentricity the minor axis of the ellipse bein«- 

 shortened, the total quantity of heat received from the sun 

 would be slightly in excess of the present, namely, by thir- 



s computed by Meech* 

 •egarded as too insigni- 



This 



may 



must 



gical speculations that if it could make itself felt, it would 

 be in an opposite direction to that which would bring about 

 glacial periods. 



It was stated at" the close of the last chapter, that the 



nd 



marked prevalence 



climates in temperat 



a 



arctic latitudes in former geological epochs, is what we 

 might have anticipated in consequence of the larger extent 

 of sea at the poles, and I have explained how slow must be 

 the conversion of the basins of deep seas into continents 

 (p. 265). Nevertheless, as in the course of millions of ages, it 

 must sometimes have happened that there was an abnormal 

 quantity of land in high latitudes, and as this geographical 

 state of things when once established would endure long 

 enough for every phase of excentricity and precession to be 

 run through, we ought to find proofs of cold or glacial in- 

 terludes m the midst of a preponderating number of warmer 



* Meech. Intensity of the Sun's Heat and Light. Smithsonian Contributions, 



VOL. I. 



T 



