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Document number: 464
Date: 11 Dec 1855
Dating: see 00089; year from 07200
Recipient: FORBES James David
Author: TALBOT William Henry Fox
Collection: Univ of St Andrews Special Collections Scotland
Collection number: MS Dep 7 nd/101
Last updated: 24th October 2009

4 Atholl Crescent, <1>

Profr Forbes

Dec 11

Dr Sir

I regret I was unable to accept your kind invitation or to stir out today.

The name which I could not recollect the other day of a newly invented galvanic coil is Ruhmkorff <2> – It is a beautiful invention – I possess one of the coils and I should be happy to lend it for exhibition at your lectures <3> if you would like to have it – It is now in Wiltshire but I have some things coming from thence in two or three weeks. The Electric light obtained makes a fine popular experiment

Yours very truly

H. F. Talbot


Notes:

1. In the West End of Edinburgh. The Talbots rented No 4 during the winter of 1855–1856 and again in 1857–1858.

2. An induction (or 'spark') coil is a transformer used to boost low voltage DC current to a high enough voltage to promote a spark. Since the magnetic field generated soon inhibits electrical flow, the coil was fed by a vibrating 'interupter' to repeatedly break off and turn on the DC current. The most popular form was devised by Heinrich Daniel Rühmkorff (1803–1877), who was born in Hanover but spent most of his life in Paris. His high-voltage induction coil of 1852 could produce sparks more than 30 cm in length. He subsequently designed a double-wound induction coil, from which evolved the alternating-current transformer of later electricity experiments. He worked with many British scientists including Joseph Bramah.

3. For Forbes’s reply see Doc. No: 07200.

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