Faraday to James David Forbes   23 July 1858

Eastbourne | 23. July 1858.

My dear sir

I received your letter & paper¹ here & it was very pleasant to hear from you; not merely for the subjects sake but for friendships sake;- & I may take the opportunity in this reply to thank you for your kind estimate of my scientific work in your history of physical science². Perhaps I have no right to thank you for what you wrote in the cause of science; but it was not the less grateful to my feelings, that I had to consider it impartial.

I have not worked on the subject of regellation since the first³. I am very glad it has been taken up by others & shall leave it for the present to them. I hold my mind therefore suspended amongst the views put forth respecting the prime cause of the effect. As however you wish me to make observations on any point I will venture one or two[.]

I do not consider the proof you give at paragraph marked 1 as sufficient to shew that metals freeze to ice at 32°⁴. That the lowest of a pile of shillings after sinking into the ice - becoming cooled to 32°. - and moulding the ice to its own rough form, should adhere to it at the bottom of the cavity, seems a very probable convergence of the roughness of the shilling & the ice; their clean contact, & the pressure of the atmosphere.- My experiments were made with gold leaf placed between two faces of ice the whole being immersed in ice cold water⁵ - the ice cold water always being prepared by pounding the ice & the water together, & leaving much of the finely powdered ice in the fluid[.]

As to Paragraph 3 ⁶ the possibility of a lower temperature within the mass of ice than at its surface was considered by me, & at the time answered in the negative as to its necessary connexion with regellation, thus:- Ice was put into a water kept at 32° externally, water added, & the ice broken up & triburated in the finest possible manner. No matter how long this was continued, - whether the water was left or poured off from time to time,- whether warm water was added to the finely divided ice & the triburation continued until one half or more was dissolved;- in every case, if a quantity of the fine particles were taken on the hand & squeezed together regellation at once took place. So also if the finest snow be scattered into water (made a little warm before hand if required) & be shaken violently up together so as to make a thorough mixture of the snow particles & the water;- still, a portion of these taken in the hand & squeezed together regellate[.]

I am only speaking of the old facts - I may add the following.- A Mr. Harrison⁷ has been manufacturing ice in London lately. He cools brine by the evaporation of ether and then lets the brine flow round metallic vessels containing water which becomes frozen. These vessels are about 1½ inch wide 20 inches long & 20 inches deep; a little narrower at the bottom, so as to give a wedge shaped plate of ice. The freezing of course begins against the metallic sides of the vessel; but as it proceeds, exceedingly fine thin crystals of ice proceed from the sides obliquely towards the middle of the water;- these often being 3 or 4 inches long, half an inch or an inch broad, and yet as thin as paper:- yet when I took one of these & held its end against the end of another. regellation occurred.

Ever My dear Sir | Very Truly Yours | M. Faraday

J.D. Forbes Esqr | &c &c &c