THE WK AGE AND ITS WORK.* 



By A. li. Wallace, F. It. S. 



I. ERRATIC BLOCKS AND ICE SHEETS. 



It is little more tbaii iifty years ago that one of the most potent agents 

 in modifying the surface features of our country was first recognized. 

 Before 1840, — when Agassiz accompanied Buckland to Scotland, the 

 Lake District, and Wales, discovering everywhere the same indications 

 of the former presence of glaciers as are to be found so abundantly in 

 Switzerland, — no geologist had conceived the possibility of a recent gla- 

 cial epoch in the temperate portion of the Northern Hemisphere. From 

 that year however a new science came into existence, and it was recog- 

 nized that only by a careful study of existing glaciers, of the nature of the 

 work they now do, and of the indications of the work they have done in 

 past ages, conld we explain many curious phenomena that had hitherto 

 been vaguely regarded as indications of diluvial agency. One of the 

 first fruits of the new science was the conversion of the author of 

 RcUqtikv JMluriancc — Dr. Buckland — who, having studied the work of 

 glaciers in Switzerland in company with Agassiz, became convinced 

 that numerous phenomena he had observed in this country could only 

 be due to the very same causes. In Novembei', 1840, he read a paper 

 before the (ieological Society on the " Evidences of glaciers in Scotland 

 and the north of England," and from that time to the j^resent the study 

 of glaciers and of their work has been systematically pursued with a 

 large amount of success. One after another crude theories have been 

 abandoned, facts have steadily accumulated, and their logical though 

 cautious interpretation has led to a considerable body of well-sup- 

 ported inductions on which the new science is becoming firmly estab- 

 lished. Some of the most important and far reaching of these induc- 

 tions are however still denied by writers who have a wide acquaintance 

 with modern glaciers; and as several works have recently ai)peared 

 on both sides of the controversy, the time seems appropiiate for a 

 popular sketch of the progress of the glacial theory, together with a 

 more detailed discussion of some of the most disputed i^oints as to 



* Selections from nrticle in Tlie Forhii(ihtli/ Heriew, November and l)eceml)er, 1893; 

 vol. Liv, pp. 616-634, 749-774. 



