3 20 THE POPULAR SCIENCE MONTHLY. 



scattered their burden of debris far and wide over its plains. The 

 conception was a bold, almost a terrifying one ; and, because the actual 

 history and nature of glaciers was so little known, it was regarded 

 with aversion and spoken of with contempt. Agassiz had laboriously 

 studied the glaciers of the Alps, he had conned the lesson they taught 

 with eager apprehension of its great significance, and he knew so well 

 every characteristic of their work that he instantly recognized abroad 

 the same indelible evidence of their past presence. 



Venetz, Rendu, and Charpentier, had preceded him in glacial 

 study, and had insisted upon an extension of the Alpine glaciers far 

 beyond their present beds in past ages, but had not realized the im- 

 mense utility of these views in explaining the glaciated surfaces of 

 Europe. Forbes, Hopkins, and Tyndall, succeeded him in the investi- 

 gation of glacial physics, and by their close scrutiny into the constitu- 

 tion of ice, and the laws of ice-making and glacial motion, fairly 

 established a new department of physical science, and added confir- 

 mation to the views of Agassiz. 



Now, let us examine some of these singular and hitherto inexpli- 

 cable records, which elicited Agassiz's theory, and which, long before 

 they were harmonized by that assumption, had been attentively ex- 

 amined by geologists and explained upon other grounds. Further- 

 more, we will review them without reference to the theory of glacial 

 action, and only subsequently compare them with the effects now being 

 produced wherever glaciers and icebergs are at work. 



The rocks as they lie in place, the flanks and summits of moun- 

 tains to heights of 5,000 and 10,000 feet, and the surfaces of out- 

 cropping masses over immense areas of the world, are all gauged in 

 long, straight channels, sometimes a foot deep, sometimes eight feet 

 deep, with widths from two to three feet. These grooves, of all di- 

 mensions, pass over the rock in groups like mouldings, and the rocks 

 they occur upon are polished and oftentimes lustrous. The channels 

 diminish in size to the faintest striae, which, like sharp scratches, cover 

 the surface, running along at times in parallel series, or diverging in 

 different directions, as though the great primitive plane had varied 

 its course over them, scouring with exquisite fineness. 



These lines and runnels score the rocks over the Northern United 

 States and Canada, throughout Europe, in Asia, and over the shores 

 of South America. We discover almost instantly that in the same 

 region they have the same direction ; that they seem, as it were, to 

 stream with us from the north ; and that, wherever other scores con- 

 travene this, these secondary markings are themselves harmonious, 

 indicating some subsequent action upon the rock, in character similar 

 to the first, though varying in its motion, and probably restricted in 

 its extent and importance. Thus the scores upon the rocks of New 

 England point northwest and southeast, and only local derangements 

 disturb this prevalent direction. The easting increases as we progress 



