Faraday to James Thomson   4 August 1858

Royal Institution | 4 August 1858

My dear Sir

I receive it as very kind of you that you should send me the Belfast report of your paper on Ice &c¹. I knew of, & have been very much interested with, your views respecting ice, & the effect generally of pressure on the fusing point. Profr. W. Thomson told me of them long ago². All the reasoning in the report I accept as truth; though I may hesitate in supposing that it contains the whole of what concerns the assumption of the solid or the liquid state by a particle of water under given circumstances[.] It is curious & interesting to observe how much the general question has drawn attention.- Forbes is thinking about it - so is Tyndall & others also in Paris. The peculiar supposition of a stickiness of the ice, at the freezing or solidifying point is interesting; but one wants some better proof than, or additional proof besides, the fact of regellation[.] I have not worked at the subject of late but I could not make ice stick to gold or metal at 32°; and I do not think that Forbes shilling is any proof of it³[.]

Being sure that your principle is correct, which requires pressure & its variations;- & admitting stickiness, simply because I am not prepared to deny it;- I am at present strongly of opinion that there is another efficient cause of regellation to which I think I have referred in the old Athenaeum report⁴:- but I have not that here & therefore cannot clearly say. It seems to me that a particle of water touching ice on one side and water at the same temperature on the other, is not so apt to change its state for that of ice as another touching ice on both sides;- and this, not as the consequence of any very limited peculiarity in water & ice - but in subordination to a far more general law, if I may so call it, that in bodies of the same kind the particles tend to retain the state of those which surround them. Thus water may be cooled many degrees below 32°F. but a particle of the water in the midst of the cooled mass remains as water though colder than ice:- and yet a warmer body than itself, as for instance a specula of ice, touching it on one side & so breaking up the continuous liquid contact around it; instantly makes it solidify - In the same manner I can conceive that a particle of ice in the middle of ice may be raised with the mass to a higher temperature before it become[s] water than a particle of the same ice at the surface, can. This change from ice to water & water to ice, being independent of any effect of pressure.

We have an illustration of this effect in water also, when it changes from the liquid to the gaseous state, instead of from the liquid to the solid state. It is given as in Donnys⁵ beautiful results⁶; where he shews that water freed from air, may be heated to I think 300°F under the pressure of one atmosphere only, and yet not boil or be converted into vapour within, though the introduction of the minutest bubble of air will cause it to explode:- a given liquid particle in the mass not being able at this high temperature to change its state into that of vapour whilst in contact on every side with liquid particles like itself though if once the contact of these particles be broken in any point, they will burst with violence into the new state.

Great numbers of other case[s] of this kind may be found amongst bodies able to change their state but they will readily occur to you. I am about to reprint my report from the Athenaeum in a Volume of Experimental Researches on Physics⁷; & think I shall arrange these views into some kind of form so as to give them a place beside your views & those of Forbes & others⁸[.] You have them uncorrected by any experiments except those of former time for I have made none lately though I have seen Tyndalls⁹[.]

Believe me to be | My dear Sir | Most truly Yours | M. Faraday

Profr. | J. Thomson C.E. | &c &c &c