and on the Conservation of Fo)rce. 165 



in favour of tlie view. If hydrated crystals of sulphate of soda, 

 carbonate of soda, phosphate of soda, &c.*, be carefully pre- 

 pared in clean basins, by spontaneous evaporation of the water, 

 they will retain their form unbroken, and their hydrated state 

 undisturbed, through the high temperatures of a whole summer, 

 though, if broken or scratched even in winter, they will commence 

 to effloresce at the place where the cohesion, and with it the 

 balance of force, was disturbed, and will from thence change 

 progressively throughout the whole massf. As regelation con- 

 cerns the condition of water, there is perhaps no occasion to go 

 further. Such facts as the following, however, concern the ex- 

 tension of the principle, and illustrate the power of cohesion, 

 especially in cases where it is coming into activity. Camphor 

 in bottles, or iodide of cyanogen in proper glass vessels, produces 

 crystals sometimes an inch or two in length, which grow by 

 the deposition of solid matter on them from an atmosphere 

 unable to deposit like solid matter upon the surrounding glass, 

 except at a lower temperature. Crystals in solution grow by the 

 deposition of solid matter on them which does not deposit else- 

 where in the solution. Many suchlike cases may be produced. 



Returning to the particular case of regelation, it is seen that 

 water can remain fluid at temperatures below that at which ice 

 forms, by virtue of the cohesion of its particles ; and in so far 

 the change is rendered independent of a given temperature. 

 Next, I rest on the fact that ice has the same property as 

 camphor, sulphur, phosphorus, metals, &c., which cause the 

 deposition of solid particles upon them from the surrounding 

 fluid, that would not have been so deposited without the pre- 

 sence of the previous solid portions, — a fact sufficiently proved by 

 the growth of flue crystals of ice in ice-cold water. This efi'ect 

 was admirably shown in Mr. Harrison^s freezing apparatus, 

 where beautiful thin crystals of ice, six, eight, and ten inches 

 long, would form in the surrounding fluid ; and these crystals, 

 which could not be colder than the surrounding fluid, exhibited 

 the phfcnomena of regelation when purposely brought in con- 

 tact with each other. 



The next point may be considered as an assumption : it is 

 that many particles in a given state exert a greater sum of their 

 peculiar cohesive force upon a given particle of the like substance 

 in another state than few can do ; and that as a consequence 

 a water particle with ice on one side and water on the other, 



* Philosophical Transactions, 18.3-1, p. 74; or Exp. Res. Electricity, vol. i. 

 p. lyi, note. 



t Such a case shows combined sohd water at a temperature ready to 

 separate and cliange into vapour, yet not changing, because, as far as we 

 can sec, tlic undisturbed cohesion holds all together. 



