Gerard Moll to Faraday   7, 9 and 10 June 1831

Utrecht 7 June 1831.

My dear Sir!

All I can say in answer to your kind letter of 30th last, is that you have my full authority to print my paper where and in such a form as you may think proper1. I am however with you of opinion, that if it is to have any good effect, this must arise principally from the circumstance of its being written by a foreigner. I have however not the slightest objection if it is at all thought expedient to let the editor of the Quarterly [Review] publish it as he pleases2; only I do not wish to see any alteration made in my statements. I was indeed exceedingly astonished to see the Quarterly adopt Babbage’s notions, and even going beyond them3. I would have been much less surprized if it had been the Edinburgh [Review] but something strange must have crossed the minds of the editors of the Quarterly, to allow such things to find their way, in a Journal which has a right to call itself so eminently english.

I have been toiling very much these days, in endeavouring to repeat the American electro-magnetic experiments, but without success4. I could not convince myself that by increasing the number of coils the power of the temporary magnet was increased in the least degree. First, the horse shoe of weak iron of 26 inches long, and one inch in diameter, was coiled round with 79 feet, of brass bell wire of 1/16 inch diameter, in 5 different and successive coils, making in all 251 turns, and weighing about 5lb in all. The galvanic apparatus consisted of a copper trough in which a zink [sic] plate of [blank in MS] feet square was inserted. It supported about 56lb.

The same horse shoe, which I had used in former experiments, was coated with silk, over this was coiled an iron spiral of [blank in MS] inch thick making [blank in MS] turns. Over this coil a second silk coating was put and over this second silk bag, a second coil, similar to the first. Using the same galvanic apparatus of my former experiments, the horse shoe was unable to carry an anvil of 202 lb, but it very freely took 180 lb. Therefore no increase of power whatever was obtained. Finding myself thus foiled in this attempt, I endeavoured to try what effect a very small galvanic apparatus would have, on a large horse shoe.

A horse shoe of 24 inch in length (when stretched out) and weighing about 29 lb and 2 inches thick, was coated in silk and surrounded with one coil of iron wire of [blank in MS] inches thick. The galvanic apparatus was a small brass trough with a zinc plate of 9 inch square, the weight supported by the temporary magnet was about 8 3/4 lb.

A larger horse shoe of 3 inches thick, and 22 inches arch diagram was now taken, coated, as usual, with silk, and a spiral of iron coiled round it 3/16 of an inch thick, and making 165 turns. The weight of this horse shoe and coil was about 102 lb. It was first ascertained that the horse shoe, did not possess magnetism sufficient to support a sewing needle, and a miniature galvanic trough was put in action, its zinc plate had not larger surface than 7/8 square inch. diagram And this sketch represents its real size. The horseshoe, by the means of such a feeble power, became capable of supporting 7 lb. The conducting fluid (1/60 nitric acid 1/60 sulphuric acid diluted) did not exceed one drachm, it was little more indeed than a thimble could contain.

This experiment appears rather curious, especially, as it would seem that, when large galvanic apparatusses [sic] are used, the force which the sam<<e>> magnet acquires, does not increase very materially when a stronger galv<<anic>> power is used. In all these experiments I always used one zink [sic] plate in a copp<<er>> trough.

I shall be very happy to learn whether you have been more successful in repeating the American experiments. My anvil of 202 lb is still a limit to which I have been gradually approaching, but which I have not yet been able to reach.

9th June My temporary magnet supported today 240 lb; I could not go beyond. The zink [sic] plate had 7 square feet surface.

10h June 1831. It supported 254 lb, but I could not obtain more[.]

John Gibson Lockhart (1794-1854, DNB).
Henry, J. (1831).


HENRY, Joseph (1831): “On the application of the principle of the galvanic multiplier to electro-magnetic apparatus, and also to the development of great magnetic power in soft Iron, with a small galvanic element”, Am. J. Sci., 19: 400-8

Please cite as “Faraday0497,” in Ɛpsilon: The Michael Faraday Collection accessed on 30 July 2021,