CHAP. XV, EXTINCT GLACIERS OF ITALIAN ALPS. 305 



fx'om a similar scrutiny of the boulders and pebbles of the ter- 

 minal moraine of one of the old extinct glaciers, namely, that 

 of the Rhone in the suburbs of Soleure. Thus, at the point 

 K, in the map, fig. 42, p. 299, 1 observed a mass of unstratlfied 

 clay or mud, through which a variety of angular and rubbed 

 stones were scattered, and a marked proportion of the whole 

 were polished and scratched, and the clay rendered so com- 

 pact, as if by the incumbent pi-essure of a great mass of ice, 

 that it has been found necessary to blow it up with gun- 

 powder in making railway-cuttings through part of it. A 

 marble rock of the age of our Portland stone, on which this 

 old moraine rests, has its surface polished like a looking-glass, 

 displaying beautiful sections of fossil shells of the genera 

 Xerinsea and Pteroceras, while occasionally, besides finer 

 BtriaB, there are deep rectilinear grooves, agreeing in direction 

 with the course in which the extinct glacier would have 

 moved according to the theory of M. Guyot, before explained. 



Extinct Glaciers of the Italian Side of the Alps. 



To select another example from the opposite or southern 

 side of the Alps. It will be seen in the elaborate map, re- 

 cently executed by Signor Gabriel de Mortillet, of the 

 ancient glaciers of the Italian flank of the Alps, that the old 

 moraines descend in narrow strips from the snow-covered 

 ridges, through the principal valleys, to the great basin of the 

 Po, on reaching which they expand and cover large circular 

 or oval areas. Each of these groups of deti'itus is observed 

 (see map, p. 306) to contain exclusively the wreck of such 

 rocks as occur in situ on the Alpine heights of the hydro- 

 graphical basins to which the moraines respectively belong. 



I had an opportunity of verifying this fact, in company with 

 Signor Gastaldi as my guide, by examining the erratics and 

 boulder formation between Susa and Turin, on the banks of 



