141 



February 25, 1858. 



WILLIAM R. GROVE, Esq., Vice-President, in the Chair. 



Charles Piazzi Smyth, Esq., was admitted into the Society. 

 The following communications were read : 



I. " Remarks on the interior Melting of Ice." By Professor 

 WILLIAM THOMSON, F.R.S. In a Letter to Professor 

 STOKES, Sec. R,S. Received January 23, 1858. 



In the Number of the ' Proceedings ' just published, which I received 

 yesterday, I see some very interesting experiments described in a 

 communication by Dr. Tyndall, " On some Physical Properties of 

 Ice." I write to you to point out that they afford direct ocular 

 evidence of my brother's theory of the plasticity of ice, published in 

 the ' Proceedings ' of the 7th of May last ; and to add, on my own 

 part, a physical explanation of the blue veins in glaciers, and of 

 the lamellar structure which Dr. Tyndall has shown to be induced 

 in ice by pressure, as described in the sixth section of his paper. 



Thus, my brother, in his paper of last May, says, " If we com- 

 mence with the consideration of a mass of ice perfectly free from 

 porosity, and free from liquid particles diffused through its substance, 

 and if we suppose it to be kept in an atmosphere at or above Cent., 

 then, as soon as pressure is applied to it, pores occupied by liquid 

 water must instantly be formed in the compressed parts, in accord- 

 ance with the fundamental principle of the explanation I have pro- 

 pounded the lowering, namely, of the freezing-point or melting- 

 point, by pressure, and the fact that ice cannot exist at Cent, under 

 a pressure exceeding that of the atmosphere." Dr. Tyndall finds 

 that when a cylinder of ice is placed between two slabs of box-wood, 

 and subjected to gradually increasing pressure, a dim cloudy appear- 

 ance is observed, which he finds is due to the melting of small por- 

 tions of the ice in the interior of the mass. The permeation into 

 portions of the ice for a time clear " by the water squeezed against it 

 from such parts as may be directly subjected to the pressure," theo- 

 retically demonstrated by my brother, is beautifully illustrated by 



VOL. IX. L 



