On the Excavation of the Valleys of the Alps. 377 



such an equation is the expression of a physical truth may be 

 regarded as the substance of the foregoing remarks. 



By applying the principles that have been set forth to the 

 relations subsisting between the temperature and the volume of 

 gases, we find that the sinking of a mercury column by which a 

 gas is compressed is equivalent to the quantity of heat set free 

 by the compression ; and hence it follows, the ratio between the 

 capacity for heat of air under constant pressure and its capacity 

 under constant volume being taken as =1*42], that the warm- 

 ing of a given weight of water from 0° to 1° C. corresponds to 

 the fall of an equal weight from the height of about 365 metres*. 

 If we compare with this result the working of our best steam- 

 engines, we see how small a part only of the heat applied under 

 the boiler is really transformed into motion or the raising of 

 weights ; and this may serve as justification for the attempts at 

 the profitable production of motion by some other method than 

 the expenditure of the chemical difference between carbon and 

 oxygen — more particularly by the transformation into motion of 

 electricity obtained by chemical means. 



XLIX. The Excavation of the Valleys of the Alps. 

 By A. C. Ramsay, F.R.S.f 



IN the month of March last I read a memoir to the Geological 

 Society on the Glacial Origin of the Swiss and other Lakes, 

 which has since been published in that Society's Quarterly 

 Journal for August. In that memoir I incidentally alluded 

 (p. 200) to the existence of the chief Alpine valleys before the 

 glaciers attained their greatest extension, which valleys were 

 afterwards " modified in form by the weight and grinding power 

 of ice in motion." 



In a previous memoir, published in 1859, I stated that "it is 

 certain all glaciers must deepen their beds by erosion, and it 

 may be that, when a glacier filled a valley " almost to the brim, 

 " the thickness of the ice was not equal to the present mass added 

 to the superincumbent weight indicated by the signs (striation, 

 &c.) on the slopes above the present surface of the glacier." But 

 though glaciers certainly have a powerful effect in deepening 

 their beds, it has always appeared to me a difficult and perhaps 

 an impossible point to determine to what extent the great Alpine 

 valleys have been eroded by ice — whether, in fact, they have 

 been chiefly scooped out by it, or whether, as I always believed, 



* When the corrected specific heat of air is introduced into the calcula- 

 tion this number is increased, and agrees then with the experimental de- 

 terminations of Mr. Joule. 



t Communicated by the Author. 



Phil. Mag. S. 4. Vol. 24. No. 162. Nov. 1862. 2 C 



