28 THE CANADIAN NATURALIST. [Feb. 



imagine, as Dr. Falconer lias forcibly put it, that the glacier which 

 is supposed to have occupied the Lago Maggiore, for example, and 

 had advanced its moraines into the plains of the Po, should have 

 had the power to plough its way down to a depth of 2000 feet 

 below the Mediterranean, and then to rise up along an incline at 

 the rate of 180 feet per mile? Nor can I admit the possible ap- 

 plication of this ice-excavating theory wherever I see that a depres- 

 sion in which a lake occurs is at right angles to the discharge of 

 an old main glacier. This is remarkably to be noticed in the case 

 of the Lake of Geneva, which trends from E. to w., whilst the 

 detritus and blocks sent forth by the old glacier of the Rhone 

 have all proceded to the N. and n.n.w. ; or in direct continuation 

 of the line of march of the glacier which issued from the narrow 

 gorge of the Rhone. By what momentum, then, was the glacier 

 to be so deflected to the west that it could channel or scoop out, 

 on flat ground, the great hollow now occupied by the Lake of 

 Geneva ? And, after effecting this wonderful operation, how was it 

 to be propelled upwards from this cavity on the ascent, to great 

 heights on the slopes of the Jura mountains ? 



Still stronger objections exist to the application of the excava- 

 tion theory to the Lake of Constance. There. I have never been 

 able to see on the northern flank of the Hohe Sentis, which pre- 

 sents its abrupt, precipitous, and highly dislocated and contorted 

 Jurassic and cretaceous rocks to the lake, with terraces of miocene 

 deposits, at various heights, — there I have been unable, when with 

 my indefatigable friend and companion, M. Escher von der Linth, 

 who knows every inch of the ground, to trace the signs of the 

 action of a great glacier, which could, in its descent, have so plunged 

 into the flat region on the east and north, as to have scooped out 

 the cavity in which the Lake of Constance lies. In this case, indeed, 

 there are no traces whatever of those great old moraines from the 

 relics of which we infer that glaciers have formerly advanced ; the 

 level country to the north of the lake being entirely free from 

 them. 



Great orographic depressions and deep cavities, sometimes dry, 

 sometimes filled with water, occur in numberless countries where 

 no glaciers ever existed. Thus, in Spain, as my colleague, M. de 

 Verneuil assures me, the large depressions on either side of the 

 granite mountains of the Guadarramma present exactly the appear- 

 ance which a theorist might attribute to excavation by ice, and 

 yet, however these cavities were formed, it is certain that no glacier 



