and the evidence of their having existed in Britain. 569 



Nov. 4.— A paper was read on Glaciers, and the evidence of their 

 having once existed in Scotland, Ireland, and England, by Professor 

 Agassiz, of Neuchcitel. 



M. Agassiz commences by observing, that the study of glaciers is 

 not new, as Scheuchzer visited, and even drew, most of the glaciers 

 of Switzerland ; and as, at a later period, Gruner and De Saussure 

 examined them in great detail, and left few of their phfenomena 

 uninvestigated. Hugi also, in his account of the Alps, and Scoresby, 

 in his descriptions of the arctic regions, have communicated much 

 valuable information respecting glaciers, but without giving rise 

 to any important geological results. Venetz and De Charpentier 

 first ascribed to the agency of glaciers, the transport of the erratic 

 boulders of Switzerland, supposing that the Alps formerly attained 

 a greater altitude than at present, and that the glaciers extended to 

 the plains of Switzerland, and even to the Jura. This assumed 

 greater height of the Alps AI. Agassiz dissents from, as no geolo- 

 gical phaenomena compel him to admit it ; and the arrangement of 

 the boulders proves that the blocks were not pushed forward by the 

 glaciers, as conjectured by M. de Charpentier. Moreover, the phse- 

 nomena of erratic boulders extend over all the temperate and north- 

 ern regions of Europe, Asia and America, and, consequently, could 

 not depend upon so local an event as a greater altitude of the Alps. 

 The consideration of these difficulties induced M. Agassiz to resume 

 the study of glaciers ; and after devoting the suitable portion of five 

 successive summers to the study of their details, and all that has 

 been written respecting their structure, he has arrived at the con- 

 viction, that the formation of glaciers did not only depend upon the 

 actual configuration of the globe, but was also connected with the 

 last great geological changes in its surface, and with the extinction 

 of the great mammifers which are now found in the polar ice. 

 He is also convinced that the glaciers did not advance from the Alps 

 into the plains, but that they gradually withdrew towards the moun- 

 tains from the plains which they once covered. In this belief, he says, 

 he is supported by many considerations which escaped previous ob- 

 servers, depending chiefly on the form and relative position of the 

 erratic blocks, and the commonly called diluvial gravel, the former 

 being in Switzerland always angular, and resting on the latter, 

 which consists of rounded materials. Considered in this point of 

 view, glaciers assume an entirely new importance, for they introduce 

 a long period of intense cold between the present epoch and that 

 during which the animals existed, whose remains are buried in the 

 usually called diluvial detritus. 



Having estalilished his theory as completely as he could, by rc- 

 j)eated investigations of Switzerland and the adjacent portions of 

 France and Germany, M. Agassiz became desirous of investigating 

 a country in which glaciers no longer exist, but in which traces of 

 them might be found. This op])ortunity he has recently enjoyed, 

 by examining a considerable part of Scotland, tlie north of England, 

 and the north, centre, west and soutli-west of Ireland; and he has 

 arrived at the conclusion, that great masses of ice, and subsequently 



