64 THE CLIMATES OF THE GEOLOGICAL PAST 



regions, and all the vapour formed in the warm zone would 

 be precipitated at the snow-line. \\'here a great and con- 

 tinuous ice-barrier would form. North of the ice-barrier 

 of the northern hemisphere, and south of that of the 

 southern hemisphere, no snow would fall, and the ground 

 might be perfectly free from sncw and ice. 



Cr oil's theory and Adhemar's hypothesis, and many 

 other speculations are scientific curiosities of great interest, 

 and are well known. Croll's hyi^othesis, though spurned 

 by many, has such merits that even to-day it must be 

 ranked as one of the best attempts ever put forward to 

 explain the cause of an ice-age. 



NOTE m THE CALCULmON OF PERCENTAGES 

 FROM VOLUMETRIC^ WORK. 



By FRANK E. CONNAH. 



Read before the Royal Society of Queensland, 2bth September, 



1909. 



