Mr. HOPKINS, ON THE MOTION OF GLACIERS. 



63 



and tlierefore, 



/=(>-! 



JV sin a. 



The central portion abb' a' in the preceding diagram will be retarded by the force 2/, 

 and therefore, since its weight = 2«o,, we shall have 



/i = ( 1 - y-j Wi sin a, 



a being the inclination of the bed of the glacier. The second portion, of which the weight = w^, 

 will l)e retarded by ./L — /i, and, therefore, 



We shall therefore have the following series of equations : 



/,-o=(,-|j 



w, sin a. 



