6 Mr. J. Ball on the Cause of the Descent of Glaciers, 



est, by the formation of " liquid flowers"*. The internal sur- 

 faces of each of these, and also of the cells containing water and 

 air that abound in glacier-ice, are so many surfaces of easy melt- 

 ing : and instead of the work of the sun's rays in melting the ice 

 being confined to the external surface, as Mr. Moseley imagines, 

 it is going on simultaneously at thousands of separate centres, 

 until in a few hours a thickness of several inches of ice is reduced 

 to that crumbling condition familiar to alpine travellers. 



I confess that, with all my respect for its author, I should 

 not have thought that Canon Moseley's theory of glacier-motion 

 required so much consideration, if the managers of the Royal 

 Institution had not invested it with a certain claim to notice by 

 giving it a place in their programme for Friday evenings. It 

 appears to me to be a further illustration of a now familiar truth, 

 that learning and ingenuity, when divorced from a constant re- 

 ference to the facts of nature, avail but little to interpret her 

 operations. 



I now venture to offer some remarks on the objections urged 

 by Canon Moseley against the received theory of glacier-motion. 

 These must be supposed to be weighty, since they have so much 

 impressed such writers as Mr. James Croll and Mr. W. Ma- 

 thews ; but perhaps these gentleman have been overmuch inti- 

 midated by the mathematical apparatus brought to bear against 

 their previous convictions ; and when the assumptions that lie 

 behind Mr. Moseley's formulas come to be carefully examined, it 

 may be found that they do not correspond with the true condi- 

 tions of the problem. 



Let us remember what the facts are that Mr. Moseley main- 

 tains to be incompatible with the theory that the motion of gla- 

 ciers is caused by gravitation acting upon a mass possessing those 

 peculiar physical properties which have been shown to appertain 

 to ice. The supposed difficulty arises from the fact that the 

 motion of a glacier is not uniform throughout every point in its 

 transverse section, but approximates to that of an imperfect fluid. 

 The central portion moves faster than those near the banks ; and 

 the motion near the surface is more rapid than that of the deeper 

 parts. It is true, as Mr. Moseley contends, that this involves a 

 relative displacement of the particles of ice; but what is its 



* In his lecture before the Royal Institution, Canon Moseley says " Tyn- 

 dall, having sent a beam of heat through a block of Wenhara Lake ice, saw 

 its course starred by the dilatations of the ice." This is a strange miscon- 

 ception. As Professor Tyndall pointed out in his paper read before the 

 Royal Society, the water in the " liquid flowers " occupies less space than 

 the ice-crystals that previousiy filled the same cavity, and it is to this fact 

 that their visibility is due. 



