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Document number: 4629
Date: 24 Oct 1842
Recipient: TALBOT William Henry Fox
Author: HENLEY William Thomas
Collection: British Library, London, Manuscripts - Fox Talbot Collection
Collection number historic: LA42-75
Last updated: 29th April 2012

23 Red Lion Street
24th Octr 1842

Respected Sir,

I beg leave to state the result of the experiment you instructed me to make – Having an Engine at home in which Contact is broken as in yours I found placing oil in the Cup over the Mercury entirely prevented the Currant [sic] passing, on cleaning it out and substituting water, the currant passed, & the spark was greatly diminished, say to one tenth but, in a few minutes the water became quite tinted shewing that oxidation was still going on, at the same time it appeard [sic] to me that the power of the Machine was diminished also –

Permit me to say a few words respecting the contact-breaking apparatus – in the Engine tried on Saturday – in the first place, the possibillity [sic] of such an occurrence as took place then can be entirely obviated by reducing the depressed part of the [illegible] so that the points shall be raised a half Inch out of the Mercury in stead of a quarter in fact, in practice the points might be raised an Inch above the edge of the Cup – rendering it absolutely impossible for contact to be made at improper times – I spent a great deal of time, and, tried no less than four different kinds of Breakpeices [sic] in that Engine – amongst the rest, I tried one formed of Ivory with segments of Brass as recommended by Professor Wheatstone; <1> but found that with a powerful Battery, it would not go above five minutes, the Brass in that time, was so acted on by the spark, that little pits were formed next the Ivory – and, being filled with oxide formed as complete a nonconducter [sic] as the Ivory itself – Still this will answer very well for weak currents – After many trials I adopted the present arrangement (altho’ much more troublesome to make than the other) as I found it to answer the best – I also beg leave to mention a large Engine that I have constructed on Professor Wheatstone’s plan – he having mentioned that you intended to have a large one made – I took the liberty to make one, in the hope that if found to work well – you would become a purchaser – it is finished and works well – altho’ not possessing the power of yours – if agreeable to you I shall be happy to submit it to your notice on Tuesday at Kings College (12 o’Clock) It is fitted up with two Magnets but, more can easily be added – the Wheel can also be detatched [sic] from the shaft, and, any other form substituted in a few seconds – In the hope that it will give satisfaction

I am Respected Sir Your Most Obt Servant
W. T. Henley

H. F. Talbot Esqre

H. F. Talbot Esqre
31. Sackville Street

P. Pd


1. Sir Charles Wheatstone (1802–1875), scientist.

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