Bird Migration from America to Europe 71 



considered as proven. Furthermore, the work of the 

 United States Astro-Physical Observatory, as may be seen 

 in the recently issued report, is favourable to the same 

 conclusion as that reached by Prof. Schaberle. 



This is not the place to state even briefly the principles 

 of Dr. Manson's theory. I may say, however, that it 

 makes clear and logical the various climates which have 

 ruled upon the surface of this globe since life began, and 

 that it has made adherents in the ranks of science from its 

 announcement. Physicists, geologists, and astronomers, 

 these have accepted the theory because of that unity and 

 simplicity which distinguishes it from the many compli- 

 cated and laboured dissertations on the subject which 

 crowd our book-shelves. I shall not say that its accept- 

 ance has been universal. That could not be. There are 

 two many who ' ' do not wish to be disturbed " even in the 

 ranks of science to permit such a result. The majority, 

 however, of those who approach the subject in a fair, 

 unprejudiced manner are accepting Dr. Manson's con- 

 clusions. 



Almost without exception, however, scientists are 

 agreed that previous to the period termed the glacial or 

 ice age, climates were non-zonal — that is, that they were 

 of the same general temperature everywhere from pole to 

 pole. First, that there was an epoch of torrid heat fol- 

 lowed by one of tropical heat and succeeded by one of 

 temperate heat, which gradually passed into one of ex- 

 cessive cold, during which period the higher lands were 

 snow-covered. From these regions descended those 

 immense glaciers, many reaching the sea level. Since 

 this ice age climates have become zonal — a condition 

 which seems to us most natural, because man remembers 

 naught to the contrary. 



The geological record shows us, however, that every- 

 where from pole to pole the same life existed during all 

 the periods before the latter part of the temperate tertiary 

 epoch. This implies that the ranges of all the various 

 species were then vastly wider. Fossil sequoias and 

 poplars found in the Arctic complete families mostly found 

 on the Pacific coast. 



