Wilhelm Martin Logeman to Faraday   5 April 1850

Mr. M. Faraday Esq. | London.

Sir!

I have the honour to send you by this a magnet of 0,98 English Pounds or 0,449 kilogrammes weight, which, when loaded with convenient precautions such as have been indicated among others by Haecker¹, in Poggendorff’s Annales der Physik und chemie, vol 57 page 335², can support a load of more as 27 English pounds or 12,30 kilogrammes. This power is constant and does not diminish even when the anchor is forced abruptly from the poles, several times in succession.

The numerous experiments of Haecker have enabled him to fix the power of a magnet of n kilogrammes weight at 10,33n2/3³, and examining those produced by the best Workshops in Europe, they are found not to attain or at least not to surpass considerably the power, indicated by this formula. The magnet you receive here, has twice this power and, with a piece of post paper, interposed between the poles and the soft iron armature, he will support stil[l] a load equal at least to that supported directly by the best magnets of the same weight hitherto produced.

This magnet is constructed after a new method, the fruit of the investigations made by Mr. Elias⁴ of this town. I am able to procure magnets of the same quality supporting 400 and even 600 English Pounds at very moderate prices.

I hope Sir, you may agree this magnet as a mark of my regard for you. If after examining it, you find it worth your approbation perhaps you may have the kindness to honour me with some lines and to communicate it among the scientific public in England in such a manner as you might think most convenient.

I am, Sir with much respect | Your humble servant | W.M. Logeman.

Haarlem 5 April | 1850.

Adres./ W.M. Logeman, | Optician | in Haarlem (Holland).

Our small horseshoe magnet weighs 7lbs. 14 1/2oz. is nearly as the

lifts 40lbs or 41 lbs law 10.33.W2/3

Logeman magnet weighs 0,98lbs.

lifts 26lbs.

Endorsed: No 4489.

Address: Mr. Faraday Esq | London