292 



VAUI 



[Ch. XIII. 



excentricity occurred. 



formula 



He 



years 



ago * and that no other excentricity approaching to 

 amount could be obtained by going back half a million 



from 



The difference between the 

 time alluded to by Mr. 



million 



mum the difference was about fourteen million. At present 



million 



are expressed by the figures 3-11-14. 



-m * 1 • 1 



Hence 

 may ha 

 existence 



maximum 



but slightly 



must 



before the beginning of the present century. 5 On this subject 

 I may observe, that when we are endeavouring to appreciate 

 iu p-PFppfs on climate to which excentricity alone may con- 



tribute, we are always mor 



likely to be correct in our 



estimate 



remote, because this cause is less likely to have been con- 

 trolled by altered geographical circumstances. If, for ex- 

 ample, an astronomer should tell us of a large excentricity 

 which' took place a million or more years before our time, 

 and we were to speculate on its connection with the Glacial 



t easily fall into the error of attributing to 

 cause what was really due to an altered 



mi 2 



astronomical 



ra 



latitudes at the period in question. For we are sure that 

 considerable fluctuations in the position and in the height 

 and depth of land and sea would have taken place in a million 

 of years, but in proportion as the date of the large excen- 



remote, the objection becomes 



Mr. Croll, following up the series of calculations begun by 



Mr 



com 



million 



a.d. 1800. 



I have taken the two first columns of the annexed 



* Letter to the author, May 15, 1865 ; and see Phil. Mag., June, 1865. 



