THE OBLIQUITY OF THE ECLIPTIC. 413 



Several other points connected with the glacial period 

 would receive a natural explanation if we were able to adopt 

 the suggestions of M. Adhemar and Mr. Croll. Thus M. 

 Morlot* some years ago pointed out that there are in Swit- 

 zerland evidences of several periods of cold, during what is 

 called the glacial epoch, separated by an interval of mildness. 



Of this the most striking instance is afforded by the Dlirnten 

 beds, where a layer of coal or lignite no less than 12 feet 

 thick, lies between two glacial deposits. Mr. Croll gives -f- 

 particulars of 250 borings through the surface deposits of the 

 mining districts in Scotland. Of these, 25 showed two dis- 

 tinct boulder clay beds, 10 three, 1 four, 2 five, and 1 as many 

 as six, with stratified beds of sand and gravel between ; while 

 16 have two or three separate beds of boulder clay, differing 

 in colour and hardness, but without intermediate stratified 

 beds. Mr. Geikie also has found in the south-east of York- 

 shire that certain gravel beds, which have yielded mammalian 

 remains and myriads of Cyrena fluminalis and other shells, 

 are covered by a mass of unstratified tile or boulder clay.J 



Whether M. Adhemar is right in attributing the prepon- 

 derance of ocean in the southern hemisphere to the influence 

 of the great Antarctic glacier, cannot, I think, in the present 

 state of our knowledge, be conclusively determined. There 

 can, however, be no doubt that an accumulation of snow and 

 ice at one pole would, by affecting the position of the centre 

 of gravity of the earth, attract the waters towards that pole. 

 Mr. Croll calculates that a diminution of 470 feet in the 

 thickness of the Antarctic glacier would raise the sea-level 

 at the North Pole 26 feet 5 inches, and 25 feet at the lati- 



* Bull, de la Soc. Vaucloise des + Mr. Skertchiey also considers 

 Sciences Naturelles, March, 1854. that he has found a clear case, near 

 Bibl. Universelle de Geneve, May, Brandon, in which palaeolithic brick 

 1858. earth underlies boulder clay. Other 



t Climate and Time, p. 254. geologists, however, have contested 



his interpretation of the fact. 



