[Royal Institution embossed letterhead] | 21 Albemarle St | W | 9 April 1860.
My dear Sir
Many thanks for your letter1 & for the Eclipse account2[.] I do not hope for the pleasure of seeing the eclipse but I hope you will be fortunate for you are taking great pains & care in the matter. I am glad you approve of Chances power of working but am somewhat surprized at the account you give me of an apparatus[.] Did they give no account or reason for it, either of their own or of the parties who have ordered or examined it? There ought to be no room for a mistake
As to your enquiries about the Electric spark the lamp that Prof Holmes has had constructed, practically works well; for being adjusted, an edge or object near the light throws a shadow on a distant wall whose plane does not vary. The keeper watches this shadow from time to time (or such a shadow) and if there be a change, corrects for it:- but the compensation for change of plane in the carbons, either upper or lower has been very good.- I have no fear for the place of the Magneto electric spark provided we can secure the attention of the keepers - that will not be called for more than is required by the written regulations now, or than was given by the keeper at the South foreland;- but it must be a good deal more than what is absolutely necessary for an oil lamp[.]
If the electric light should come into use it seems to me that there will be no difficulty in bringing both the vertical & the horizontal divergence easily under command.
Ever My dear Sir | Very Truly Yours | M. Faraday
G.B. Airy Esqr | &c &c &c
Please cite as “Faraday3760,” in Ɛpsilon: The Michael Faraday Collection accessed on