86 Transactions. 



lasting for thousands of years must have alternated with equally 

 prolonged periods of genial conditions, for the latter no less than 

 the former are a necessary consequence of extreme ellipticity com- 

 bined with the precession of the equinoxes." 



That the position of the earth in relation to the sun has been 

 the great originating cause of the extraordinary climatal conditions 

 which prevailed during the glacial epoch is now universally 

 admitted, but considerable difference of oi)inion prevails as to the 

 right interpretation of the testimony of the rocks ; what the vast 

 relics of the " Ice Age " really tell us as to the physical conditions 

 which then prevailed over the surface of our planet. It is 

 certainly known that the ice attained to a very great thickness, 

 for marks of its presence are to be found on the tops of mountains 

 in Canada from 3000 to 5000 feet high. It is certain that our 

 own country and part of England was in the same condition as 

 Greenland is now, and also that a large part of Northern Europe 

 and America, at a comparatively recent period, geologically 

 speaking, lay deep buried under a vast sheet of " thick ribbed 

 ice," so thick that only the i^eaks of the highest mountains stood 

 up unburied. It is held by Croll and other eminent geologists and 

 physicists that a great ice cap would gather during long thousands 

 of years, reaching far down into what is now the temperate zone, 

 and that such conditions would jsrevail for thousands of years 

 altei-nately in northern and southern hemispheres. But there are 

 other eminent physicists who maintain that glacial conditions 

 during the period of high eccentricity were simultaneous in both 

 hemispheres. Able men differ on the matter, and for the present 

 we can but regard their various and conflicting opinions as only 

 " the guesses of the wise." While there are differences of opinion 

 as to the nature and extent of glacial conditions, there is general 

 agreement that the primary cause of such conditions was the posi- 

 tion of the earth in relation to the sun. 



Local Notes. — A remarkable example of the work of the great 

 ice sheet came under my notice when the railway bridge below 

 Dalbeattie was built a few years ago. The foundation for the 

 piers of the bridge were laid at a depth of twenty or twenty-five 

 feet below the surface, or bed of the stream. The material gone 

 through was entirely boulder clay, and at the bottom, strange to 

 say, indications of an earlier earth surface and soil were found, 

 with frasioieuts of wood and hazel-nuts. 



