152 ANNUAL OF SCIENTIFIC DISCOVERY. 



water can retain its fluid condition only when in contact with ice on 

 one side, but freezes when touched by ice on both sides, the general 

 temperature remaining the same. This explanation with all defer- 

 ence be it said is simply a re-statement of the fact, and not an 

 assignment of a physical cause. Person maintains that the solu- 

 tion of ice is a gradual process, the ice passing through interme- 

 diate states of viscosity to the condition of a liquid. He considers ice 

 as essentially colder than the water in contact with it ; that a film of 

 plastic ice or viscid water lies between the ice and the water, and 

 that heat is constantly passing from the water to the ice through this 

 film. The water therefore becomes colder and finally freezes. This 

 view is adopted by Prof. J. D. Forbes. Neither Person nor Forbes ex- 

 plains why a thin film of water in contact with a mass of ice has or can 

 have any other temperature than the ice itself, nor why water at 

 should give off heat to ice at 0. Prof. James Thomson's theory is, in 

 his own words, as follows : If to a mass of ice, at its melting point, pres- 

 sures tending to change its form be applied, there will be a continual 

 succession of pressures applied to particular parts liquefaction occur- 

 ring in these parts through the lowering of the melting-points by pres- 

 sure evolution of the cold (sic) by which the so melted portions had 

 been held in the frozen state dispersion of the water so produced in 

 such directions as will afford relief to the pressure and re-congela- 

 tion by the cold previously evolved of the water on its being relieved 

 from this pressure : the cycle of operations will then begin again ; for 

 the parts re-congealed, after having been melted, must in their turn, 

 through the yielding of other parts, receive pressures from the ap- 

 plied forces, thereby to be again liquefied, and to proceed through 

 successive operations as before. This theory certainly appears to be 

 tenable in the case of glaciers, or wherever great pressures are ap- 

 plied, as in the moulding of ice under a hydrostatic press, but its 

 application is, to say the least, doubtful in the case of simple contact 

 between small masses of ice. Moreover, Faraday has shown that 

 pressure is not necessary in regelation. Of the numerous experi- 

 ments which he has instituted, the following appears to us the most 

 convincing. Two round cakes of ice, convex upon the upper sur- 

 faces, are placed in water of ordinary temperature and then sunk 

 beneath the surface by little weights of wax or spermaceti. Two 

 such pieces of ice touching each other gently at a single point freeze 

 together. In this case no sensible capillary action takes place in 

 consequence of the figures of the masses of ice. Faraday did not 

 succeed in obtaining regelation with melted bismuth, tin and lead, 

 nor with glacial acetic acid, or saline bodies. He considers the phe- 

 nomenon therefore as peculiar to water. Silliman's Journal. 



THE EXPANSION OF WATER NOT AN ANOMALY IN THE SOLID- 

 IFICATION OF LIQUIDS. 



In most works on physics, reference is made to the dilatation of 

 water when cooled down to near the freezing point, and to the bene- 

 ficent effect of ice being thus caused to float, instead of sinking and 

 choking up our rivers. The fact is also mentioned as a remarkable 

 exception to the general law of expansion of liquids in proportion as 



