XXIV RECENT PROGRESS OF THE GLACIER THEORY. 



the softened ice under pressure still appears to me to be a 

 sufficient explanation of all the appearances. Mr. Faraday's 

 most interesting observation shows, however, the extreme limit 

 of the law of graduated softening, and is, as I have recently 

 endeavoured to prove (in a short paper printed at page 228 of 

 the present volume), a consequence of M. Person's law. 



In like manner, Professor W. Thomson's interesting experi- 

 ment on the lowering of the freezing point of water under 

 pressure, and the consequent thaw of ice below 32, may 

 reasonably be included amongst the causes which, in peculiar 

 circumstances, may impart to glacier ice a portion of its plasti- 

 city. I am not disposed to ascribe to it, by any means, the 

 whole of the plastic qualities of the glacier, as Mr. James 

 Thomson seems inclined to do. In the rapid alternations of 

 pressure which take place in the moulding of ice under Bramah's 

 press, it cannot, I think, be doubted that the opinions of the 

 Messrs. Thomson are verified.* 



All these results of the discriminating study of the familiar 

 substance of ice near 32, the deduction of M. Person, the fact 

 of Mr. Faraday, the experiment of Dr. Tyndall, the prediction 

 of Mr. James Thomson and its verification by his brother, 

 instead of militating against the correctness of my Theory of 

 Glaciers of 1842, seem to me to afford so many independent 

 confirmations of it. The larger and more correct views which 

 may now be taken of the entire subject, and for which we are* 

 indebted to so many eminent men, cannot, I should hope, render 

 valueless the generalization which was made without the full 

 advantage of them. 



With these prefatory observations, I leave to the judgment 

 of the reader the historical records of my own successive endea- 



* See the very interesting experiments of M. Mousson in the Bibliotheque 

 Universelle, September 1858. 



