SS^ HEROES OF SCIENCE. 



found that these strata, separated by the great mass 

 of the mountains, resembled each other somewhat 

 mineralogically as well as in their fossils, but he 

 was not able to make out that they were exactly of 

 the same geological age, although it was highly 

 probable. He wrote on the glaciers ancient and 

 modern of the southern slopes of the Alps, and in 

 relation to the former — "A comparison also of the 

 extinct glaciers of the Italian and Swiss sides of 

 the Alps can better be made from Turin than from 

 any other place. Before my arrival I had seen, 

 on the banks of the Lago Maggiore, some good 

 examples of erratics and of moraines which had 

 come from the Simplon, but these, as you might 

 suppose, a priori are far inferior to those which 

 have descended from the Val d'Aosta, or which 

 belong to the mighty glacier derived from the com- 

 bined snows of the Mont Blanc and the Mont 

 Rosa group of Alpine heights. This glacier, 

 although perhaps of less gigantic dimensions than 

 that of the Rhone, has certainly left, as Gastaldi 

 first pointed out in a memoir on the subject, a far 

 more imposing monument of itself on the plains of 

 the Po, than have the extinct glaciers of the Rhone 

 or the Rhine, in the lower country of Switzerland." 

 He noticed that "J. D. Forbes has well shown in his 

 book on the Alps, that a glacier is a peculiarly sensi- 

 tive instrument for measuring the average of heat 

 and cold, and that every slight difference of tempera- 

 ture causes it to increase or lessen in height and 

 length." And pursuing the argument, remarks that 



