198 Prof. Forbes on. Ice aM Glaciers. 



of taking the temperature of ice unless that ice be dry. What, 

 then, is the effect of the pressure which you describe as con- 

 verting the " slush " into " solid slabs " ? You admit, with me, 

 that pressure is not necessary in the general case for regelation 

 (p. 94). The effect of the pressure, then, is merely to banish 

 nearly all the perfect water (that whose temperature the thermo- 

 meter had shown) from the mass, leaving merely films of water 

 (more or less viscid) between the still icy particles which consti- 

 tuted the slush. These particles, small as they are, contain each 

 its magazine of cold, and being numerous as they are small, this 

 cold is adequate to the consolidation of the interposed films of 

 water, precisely as when the experiment is made on larger 

 piasses. 



In this explanation I admit your view, that water is absolutely 

 frozen in the process ; but I believe also in the cohesive aggre- 

 gation or ivelding under pressure of surfaces of ice softened by 

 imminent thaw, though not yet reduced to water. 



I think that, on consideration, it will appear clear to you that 

 the preceding explanations render the facts you mention in- 

 evitable deductions from the doctrine that ice absorbs latent heat 

 gradually *. 



II. As regards the theory of the Veined Structure of Glaciers 

 (p. 94 of your paper), there would perhaps be some inconveni- 

 ence in my dictating the interpretation which certain passages of 

 my writings more than twelve years old must bear, and de- 

 claring that no other interpretation is admissible. Such an 

 affidavit of a pleader in his own cause might be received with 

 distrust. It is better that others should study what I have 

 written, and that they should conclude my meaning from an 

 impartial examination of the whole documents. To facilitate this 

 examination, I am about to publish, in a collected form, all my 

 minor papers on the Theory of Glaciers which can throw any light 

 on this question ; and I hope that then, when the difficulty of 

 fairly and fully examining what I have said on the subject has 

 been removed, my meaning will be found to be both definite and 

 intelligible. 



In the present instance, if, as stated in your paper, more than 

 one writer has attached a certain significance to the terms of my 

 Thirteenth Letter on Glaciers — and if, of these writers. Professor 

 William Thomson be one, — it is not, I think, too much to affirm 

 that it is probable that their concurring, though independent, 

 inference as to my meaning is correct. I have not myself any 

 doubt of its correctness ; but I repeat that I do not cite myself 

 as a witness in a case of interpretation which affects my own 



[* See Mr. Faraday's remarks on Regelation in our present Number, 

 p, 162.— Ed.] 



