466 Transactions. — Geology. 



tion has been insufficient without the operation of other causes 

 to bring about an ice period, nor have the depressions had any 

 apparent effect upon the flora and fauna. In Europe we are 

 told the depression of the land " preceded and accompanied 

 the appearance of the ice-sheets," and, what is stranger still, 

 " the submergence had a remarkable relation to the extent 

 of glaciation." It will be noticed how unlike the periods 

 known as Pleistocene were in the Northern and Southern 

 Hemispheres, as judged by the facts at present collected. In 

 the north the period was one mainly of depression ; in the 

 south w T e are told it was one of elevation. In the north the 

 surface -changes are said to have been frequent, depres- 

 sion and re-elevation following at regular intervals ; whilst 

 in the south few changes took place, and the physical con- 

 ditions remained almost constant. It is difficult to account 

 for such diverse interpretations of a period which has so many 

 things in common in both hemispheres, and it may be that 

 the time will come when a more perfect knowledge of the 

 physical conditions that prevailed on the earth during the 

 Pleistocene period will enable glacialists to harmonize what 

 now presents so many contradictions, and to simplify pheno- 

 mena which are too often interpreted so as to fit in with some 

 theory or other that has received the approval of geologists 

 simply as a working theory and nothing more. 



Part II. 



In striving to harmonize what appears so contradictory as 

 to the sequence of events connected with the Pleistocene period 

 in the Northern and Southern Hemispheres, it may be well to 

 refer to certain recognized facts connected with the sun and 

 the earth in relation to the other portions of the solar system. 

 Prom the sun the earth receives its heat, which reaches the 

 surface through the medium of the atmosphere. Of every 

 100 units of heat that comes within reach of the aerial ocean 

 Alexander Woeikof says that only about 60 per cent, reaches 

 the earth's surface at the equator, 55 per cent, at 20° north' 

 and south, 41 per cent, at 40°, 24 per cent, at 60°, and only 

 about 10 per cent, at the poles. Hence much more than half of 

 the amount of heat which comes within the limits of the earth's 

 envelope passes back into space without doing any effective 

 work whatever on the surface of the earth. Now, there is 

 nothing that we know of in nature which can give off any 

 portion of heat for an indefinite length of time without lowering 

 or diminishing its own effectiveness. A ton of coals has so 

 much available energy and no more: and so with respect to 

 the energy of the sun. He cannot go on for ever sending his 

 heat and light to our own and other worlds without loss of 



