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3. An Account of some Monstrosities. By the late Dr J. 

 Reid. Communicated by Prof. Goodsir. 



4. The Effect of Pressure in Lowering the Freezing-Point 

 of Water experimentally demonstrated. By Professor 

 W. Thomson, Glasgow. 



On the 2<I of January 1849, a communication, entitled "Theo- 

 retical Considerations on the Effect of Pressure in Lowerinof the 

 Freezing-Point of Water, by James Thomson, Esq., of Glasgow," 

 was laid before the Royal Society, and it has since been published 

 in the Transactions, Vol. XVI., Part V. In that paper it was 

 demonstrated that, if the fundamental axiom of Carnot's Theory of 

 the Motive Power of Heat be admitted, it follows, as a rigorous con- 

 sequence, that the temperature at which ice melts will be lowered 

 by the application of pressure ; and the extent of this effect due to 

 a given amount of pressure was deduced by a reasoning analogous to 

 that of Carnot from Rcgnault's experimental determination of the 

 latent heat, and the pressure of saturated aqueous vapour at various 

 temperatures differing very little from the ordinary freezing-point 

 of water. Reducing to Fahrenheit's scale the final result of the 

 paper, we find 



t = n X 0-0135 ; 



where t denotes the depression in the temperature of melting ice pro- 

 duced by the addition of n " atmospheres'" (or n times the pressure 

 due to 29-922 inches of mercury), to the ordinary pressure expe- 

 rienced from the atmosphere. 



In this very remarkable speculation, an entirely novel physical 

 phenomenon was predicted in anticipation of any direct experiments 

 on the subject ; and the actual observation of the phenomenon was 

 pointed out as a highly interesting object for experimental research. 



To test the phenomenon by experiment without applying excessively 

 great pressui-e, a very sensitive thermometer would be required, since 

 for ten atmospheres the effect expected is little more than the tenth 

 part of a Fahrenheit degree ; and the thermometer employed, if 

 founded on the expansion of a liquid in a glass bulb and tube, must 

 be protected from the pressure of the liquid, which, if acting on it, 



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