120 Messrs. Turpin and Warrington on the 



nitre in water at 125°. Their experiments on solubility appear 

 to stop short far below the temperature of fusion of the salt 

 per se (excepting in cases where the salt contains water of 

 crystallization). They distinctly state, however, that infinite 

 solubility is " nearly true of benzoic acid, which melts at 



120° By sealing it up with water in a glass tube and 



heating to a few degrees beyond the melting-point, intermix- 

 ture occurs in all proportions ; and the liquid so obtained, on 

 cooling to 120°, or about 1° lower, becomes turbid from depo- 

 sition of oily drops, which, however, immediately crystallize.". 

 — F. G.] 



XIII. On t fie Apparent Viscosity of Ice. By G. S. Turpi n and 

 A. W. Warrington, B.Sc, Students in the Owens College, 

 Manchester*. 



SOME years ago Mr. J. T. Bottomleyf devised an experi- 

 ment to illustrate the effect of pressure on a melting 

 block of ice. A stout copper wire with heavy weights attached 

 at its two ends is slung across a block of ice which is sup- 

 ported in any convenient manner. The wire gradually makes 

 its way through the block ; but the ice constantly re-forms 

 behind the wire, so that after the block has been cut right 

 through it is still whole and entire. The path travelled over 

 by the wire does not, however, possess its original structure, 

 but is now semi-transparent, and the block splits readily along 

 this path. 



Bottomley found that string, under the same circumstances 

 as the copper wire, would not cut through ice. The explana- 

 tion he gives is that " the string is not a good enough con- 

 ductor to relieve itself of the cold in front and pass it back to 

 the water behind.''' In this shape the explanation does not 

 seem very clear, but in the following expanded form it is 

 evident enough. When the wire starts its journey, its upper 

 surface is in contact with ice-cold water, and its lower surface 

 in contact with ice. The pressure of the wire tends to make 

 the ice beneath it melt ; but before this can occur the latent 

 heat of liquefaction must be supplied, and in the case of the 

 copper wire is readily obtained from the water above, which 

 is in consequence frozen. The newly formed water is forced 

 upwards round the wire ; and the same process is repeated 

 until the wire has made its way through the block. When, 



* Communicated by the Authors, 

 t ' Nature/ vol. v. 1872, p. 185. 



