Faraday to William Pigott   20 October 1863

Royal Institution | 20 Octr 1863

My Dear Sir

I was with Mr Daboll for two hours or more on Saturday (17th); I saw his fog horn & apparatus at work at the Trinity house & heard all his explanations & views. A two horse Ericsons¹ hot air engine works an air pump continually - the air which is condensed into an iron cylinder is permitted to pass at regular intervals into the associated trumpet or horn which is funnel[l]ed with a vibrating tongue. The sound is continued for 4 or 5 seconds & then silence exists for twice that time. On Saturday it took nearly an hour for the fire to get up sufficient heat after that the effect was very regular & good. The sound was very powerful in the experimental room but in the further rooms with the intervening doors shut - or in the front of the house it was not audible[.]

The invention is so far advanced & perfected as to justify a trial & proof on the sea shore & at sea, where it might be subject to the observation & judgment of nautical men and be compared with the steam & air trumpets of other persons & with steam whistles &c. I suppose Dungeness would be an excellent place because of the number of nautical observers there, the opportunity of observing the effect round one half or three fourths of the horizon i.e. in all directions & at any distance over the sea & the presence there already of Holmes steam trumpet[.]

As far as I understood Mr. Daboll in conversation he thinks that the experiment has been practically tried for four years at the New London light house to the full satisfaction of nautical & professional men & that their testing which is contained in a short printed paper is sufficient & ought to be so received. I can give no opinion on that point. I do not gather from him that he desires any further proof here in England. I received a letter² from him this morning in which he also says as much. I think it says too that the apparatus proposed for Cape Race was to be larger & worked with air of greater pressure than that now at the Trinity House[.]

I send his letter with this - but shall be glad to have it back again³.

I am | My dear Deputy Master | Your Very faithful servant | M. Faraday

Captn. Wm. Pigott | Deputy Master | &c &c &c