Faraday to Charles Richard Weld   6 July 1855

6 July 1855

My dear Sir

I cannot doubt that any paper by Mr. Joule must be proper for the Transactions but I am unable to judge of the peculiar merits of the one you send me¹. The object is (I conclude) to obtain data the best fitted to form the foundations of mathematical investigations into the nature of the electro-magnetic forces. Having no mathematical knowledge I am not competent to say whether the data here supplied are so direct in their consequences as to be thus fitted for that purpose. With my rough geometrical mode of looking at things I should have liked to know the number of spirals (which vary) in the different helices;- and the influence of the difference of helix diameter for the different bars:- also having a helix constant in diameter & length of wire, the difference caused by having the iron (of the same weight & length) in the form of a rod or a cylinder so as to be in one part or another of the space within the helix;- and other variations. But for ought that I know the mathematicians may not require these particularities but may be able with a given & constant length of wire to proceed at once from the data Mr. Joule gives. I have no doubt that the experiments are well & carefully made. I conclude that the iron was of like quality in all the cases & well annealed[.]

Dr. Tyndall is abroad at present:- when he returns he will have the paper & your note²[.]

I am | Yours Very Truly | M. Faraday

C.R. Weld Esq