202 WRITINGS OF JOSEPH HENRY, [1855- 



doubt tend to produce the effect we have already mentioned, 

 though it is not improbable that the melting of the ice, as in 

 the case of the evaporation of water, tends to reduce the tem- 

 perature slightly below 32°. Prof. Tyndall, of the Royal In- 

 stitution, has recently made an interesting series of experi- 

 ments on the plasticity of ice. He finds that it may be bent 

 and moulded into a variety of forms by subjecting it to pres- 

 sure, particularly when near the melting point, and has 

 very ingeniously applied this property to the explanation of 

 the stratified appearance of some of the glaciers. If pressure 

 is applied to any plastic substance in which are disseminated 

 globules of air or irregular patches of other material, the 

 mass will assume a lamellar structure at right angles to the 

 direction of the compressing force ; and in this way the 

 laminated appearance which is exhibited after the conflu- 

 ence of two separate streams of ice which exert a great 

 pressure upon each other is explained.. 



It is well known that when alcohol and water are mixed 

 together the attraction of the two bodies is so great that a 

 diminution of bulk and a consequent rise of temperature 

 ensue. The same affinity exists between ice and alcohol; 

 but when these are mixed, strange to say, a considerable 

 diminution of temperature is the result; and those who 

 habitually or otherwise mingle these two ingredients as a 

 beverage, are sometimes surprised to find the fragments of 

 ice frozen in a solid mass to the spoon by which the mixture 

 is stirred. When two liquids having an attraction for each 

 other are mingled together and a diminution of bulk ensues, 

 heat must be evolved on account of the power generated by 

 the approach of the atoms. For an analogous reason, when 

 the attraction between the atoms of two bodies is diminished 

 a quantity of heat must disappear; hence when a solid is 

 dissolved in a liquid for which the attraction is not very in- 

 tense, a quantity of heat disappears or cold is the result. In 

 the case of the alcohol and ice, the cold produced by the 

 liquefaction of the solid greatly exceeds the heat which might 

 be produced by the union of the water and the alcohol. 

 When the affinity however is very great, as between nitric 



