The Theory of Glacier motion. 127, 



end), pull the lateral and inferior parts along with them. 

 One proof, if I mistake not, of such an action is, that a 

 deep current of water will flow under a smaller declivity 

 than a shallow one of the same fluid." And this consideration 

 derives no slight confirmation in its application to glaciers, 

 from a circumstance mentioned by M. Elie de Beaumont, 

 which is so true, that one wonders it has not been insisted 

 on, namely, that a glacier, where it descends into a valley, is 

 like a body pulled asunder or stretched, and not like a body 

 forced on by superior pressure alone. 



(2) The comparatively slight difference between the 

 motion of the centre and sides of a glacier is in accordance 

 with the law prevailing with viscous bodies, that the retarda- 

 tion due to friction will be more completely distributed over 

 the whole section in proportion as the matter is less yielding. 



(3) The greatest variation of velocity in a glacier takes 

 place, as it should in a viscous body, near, the sides; and- 

 bottom, while the. higher and more central parts move most 

 nearly together. ^. :.. : : 1 



(4) Forbes confirmed, experimentally, in glaciers, Du- 

 buat's law in regard to the flow of streams, namely, that their 

 velocity at the top and bottom depends upon the actual 

 velocity of the stream, and the amount of lateral retardation 

 depends also upon the actual velocity of the stream. 



(5) A glacier, like a stream, has its still pools and its 

 rapids. When it is embayed by rocks it accumulates — its 

 declivity diminishes and its velocity at the same time ; when 

 it passes down a steep, or issues by a narrow outlet, its. 

 velocity increases. The central velocities of the lower^ 

 middle, and higher regions of the Mer de Glace, are 



- 1-398 '574 -925 



and if we divide the length of the glacier into three parts, 

 we shall find something like these numbers for its declivity,^; 



1-5 414 8 



Lastly, when the semi-fluid ice inclines to solidity, during 



