Joseph Henry to Faraday   3 November 1866

Smithsonian Institution. | Washington. Nov 3d. 1866.

My Dear Sir

I write to request that you will inform me as to what is actually doing by the Light House authorities of England in the way of experiment with the electrical light and particularly with that derived from Wilde’s apparatus.

Do not encounter the labor of giving this information with your own hand, but employ as I have done, an amanuensis.

I ask the information above-mentioned on account of the Light House Board of the United States, of which from its first organization I have had the honor to be a member. This Board consists of two officers of the Navy, two of the Army, all of high rank, and two civilians of scientific reputation, also a secretary from the Navy and another from the Engineer corps. Previous to the commencement of the war¹ I gave but little attention to the subject, the business being principally conducted by the Secretaries, but during the war the officers of the army and navy being generally withdrawn from light house duty, I was obliged to devote much more time to it than previously, and in the absence of my colleague in the Board, Prof. Bache², who is still hopelessly excluded from active life, I am the principal scientific adviser.

A few years ago the subject of the materials of lighting was referred to me, and after examining all the different oils which had been proposed for the use of the light houses, I decided upon that manufactured from lard, and have succeeded in procuring its general introduction at all the light stations on the coast, except those of the entrance of harbors in which the smallest lamps are used. It had been proved conclusively that good lard oil is superior to sperm in lamps of all orders above the sixth. The change has been attended with a saving to the Government of at least 10,000 £. st. a year.

The Board has also referred to me the subject of fog signals, and in relation to this have made a series of experiments from which it would appear that the trumpet of Daboll, in which the agitation of the air is produced by the vibration of a steel tongue, gives at least four times as much effective sound as that in air instruments in which the primary vibrations are produced by a film of air as in the ordinary whistle. The point to which we are now directing attention however, is to obtain the best kind of caloric engines or such as do not require water for the production of steam. There are three engines of this class, of which I think Ericson’s³ is the least effective. In regard to fog signals, what is the experience of the English Light-house authorities?

The results obtained by Wilde if truly represented are remarkable, though perhaps not at variance with established dynamic principles, since it would appear that the effect is only commensurate with the amount of mechanical power expended. The fact stated that an electro-magnet retains a charge of electricity similar to that of the cable is not surprising, or that this at the moment of rupturing the circuit should increase the inductive effect; but I do not see that while in its statical condition it should increase the intensity of the magnetism of the iron. I have not however seen a full exposition of the principles of the apparatus, and therefore cannot speak definitely in regard to it.

I⁴ was gratified to learn from Mrs Bache⁵ who called upon you with her husband that you were looking quite well and that though you had given up scientific research you were enjoying apparently good health. I still retain a vivid impression of my visit to England⁶ and would be delighted to have an opportunity to repeat it;- but of this I have no prospect. I am still directing the affairs of the Smithsonian Institution and perseveringly endeavouring to carry out the plans which I originally proposed[.]

I am just called on to give the opening lectures at an Institution founded in Baltimore by Mr. Peabody⁷ of London on an endowment of one million of dollars and I shall present to their Trustees the Royal Institution as a model of imitation.

Truly your friend | Joseph Henry

Dr M. Faraday