THE PARALLEL ROADS OF GLEN ROY 227 



not possibly have discerned the cause subsequently as- 

 signed for the blockage of these glens. A knowledge of 

 the action of ancient glaciers was the necessary ante- 

 cedent to the new explanation, and experience of this 

 nature was not possessed by the distinguished writer just 

 mentioned. The extension of Swiss glaciers far beyond 

 their present limits was first made known by a Swiss 

 engineer named Venetz, who established, by the marks 

 they had left behind them, their former existence in places 

 which they had long forsaken. The subject of glacier 

 extension was subsequently followed up with distin- 

 guished success by Charpentier, Studer, and others. With 

 characteristic vigor Agassiz grappled with it, extending 

 his observations far beyond the domain of Switzerland. 

 He came to this country in 1840, and found in various 

 places indubitable marks of ancient glacier action. Eng- 

 land, Scotland, Wales, and Ireland he proved to have 

 once given birth to glaciers. He visited Glen Roy, sur- 

 veyed the surrounding neighborhood, and pronounced, as 

 a consequence of his investigation, the barriers which 

 stopped the glens and produced the parallel roads to 

 have been barriers of ice. To Mr. Jamieson, above all 

 others, we are indebted for the thorough testing and con- 

 firmation of this theory. 



And let me here say that Agassiz is only too likely to 

 be misrated and misjudged ly those who, though accurate 

 within a limited sphere, fail to grasp in their totality the 

 motive powers invoked in scientific investigation. True, 

 he lacked mechanical precision, but he abounded in that 

 force and freshness of the scientific imagination which in 

 some sciences, and probably in some stages of all sciences, 

 are essential to the creator of knowledge. To Agassiz was 



