Mr. Sutcliffe's Suggestions on the Movement of Glaciers. 495 



Draw A A', B B' intersecting X X' and each other in O, 

 so that AOX = BOX = tan~'a; then it is clear that the 

 equation ^ = a a; s'm go 



indicates that the point of which j/ is the ordinate is situate 

 somewhere within one of the angles A O B', A' O B' (the sides 

 produced indefinitely) ; or in other words, y = axsin co is 

 the equation to the surface included in those angles. 



In like manner the two equations, 



?/ = a^sinQo, a; = a sin CO, 



(where O D = a) determine the triangle C O E. 



The two equations, y =^ a.x sin go, a? = «, 



determine the limited line C D E drawn perpendicular to the 

 axis of X. 



The equations, y = ax^ a; = a sin co, 



determine the limited lines C C, E E', where CO = CO 

 and E O = E O'. 



These examples are sufficient to elucidate the principle of 

 interpretation to be adopted. 



Cheltenham, March 17, 1845. 



Postscript. 



At the time of writing the above paper, the subject of which had been 

 long before me, I was not aware that my friend Mr. Earnshaw had com- 

 municated to the Cambridge Philosophical Society a paper on the same 

 subject, which has since been published. Our methods of treating the 

 subject, however, are so different, that I have thought it not unadvisable 

 to communicate the above. I cannot help observing, en passant, that Mr. 

 Earnshaw seems to treat the crude notions which have been put forth on 

 this subject, with far more respect than they deserve. 



10 Maddox Street, Bond Street. May 24 1845. 



LXX. Suggestions relative to the Theory of the Movement of 

 Glaciers. By William Sutcliffe, Esq.^ 



THE theory of glaciers is at present an object of such deep 

 and general interest in the scientific world, that a by- 

 stander, incompetent to the discussion of the entire subject, 

 may perhaps be permitted to make a suggestion or two in 

 reference to a particular point. If this indulgence is con- 

 ceded, I would venture to ask, — 



I. Whether the plasticity, so strongly indicated by the 

 phaenomena which attend the movement of glaciers, and yet 

 so little in accordance with the properties of ice as exhibited 

 under ordinary circumstances, may be due wholly or in part 

 to the influence of heat developed by intense local pressure? 

 That the pressure in the interior of a moving glacier must in 

 many cases be not only very great but very unequally distri- 

 buted is quite clear ; and the friction, when disruption takes 



* Communicated by the Author. 



