Faraday to Jacob Herbert   22 December 1846

Royal Institution | 22 Decr. 1846

Sir

On the receipt of your letter dated the 17 instant¹ respecting the decay of the lower ends of the ventilating tubes I wrote to Mr. Wilkins requiring information of the nature of the decay and specimens of the tubes that I might consider the case. He informs me that it is only at the Harwich lights that such a result has been observed and that there has been nothing of the kind at the Tynemouth lighthouse where the pipes have been up for the longest period or with other ventilating arrangements which have been erected for nearly as long a time. The evil at the Harwich lights consists in a breaking away of the edge of the socket when the one pipe fits into the other and may be due to one of two causes or conjointly to both namely the diminution of the strength of that part of the tube by the mode of working it or the roughness of the usage it is subject to in conjoining or separating the parts. I have examined the mode in which the parts are here put together & also a modification proposed by Mr Wilkins & have instructed Mr. Wilkins subject to the confirmation by the Board so to alter the joint that the parts instead of being conical shall be cylindrical & stronger than at present[.] I expect the alteration will supply all that is required[.] If there are any cases for which it should not prove strong enough there cannot be the least difficulty in making the joint of any strength desired[.]

I am glad to find that this is a simple case belonging to construction and not to principle; and one easily remedied. I was fearful that your letter referred to some more general & constant source of decay. If there should be any thing of which I am not as yet aware will you do me the favour to make me cognizant of it that I may take it into consideration. I hope to be able to go to the South Foreland in two or three weeks² and then could examine any particular effect in the case of the apparatus belonging to the lower light there³[.]

I am Sir | Your Very Humble Servant | M. Faraday

Jacob Herbert Esq | &c &c &c