Faraday report to Trinity House   27 June 1859

27 June 1859 | Royal Institution

Report on Professor Way’s electric lamp

The electric light of Mr Way has its peculiarity in the nature of the lamp. The electricity is obtained from a Voltaic battery and is so far subject to the same remarks as those which arose respecting Dr. Watsons¹ proposition & which need not be repeated here². I will therefore confine my observations to the lamp alone. I have received no written statement of the advantages of the lamp - of the amount of its lighting power - of the price of the light - of its proportion compared to any known standard - or of its proportion compared with that produced by an equal amount of electricity passing between carbon poles in the ordinary way nor any experimental data from which these points can be ascertained. I learn only by verbal communication with Dr. Way that the place of the light is unchangeable and that it has yet to be studied in respect of the above points and of its final construction dimension & adjustments[.]

A fine thread of Mercury is beautifully arranged within a glass chamber so that when an electric current of sufficient strength is passed through it the thread is broken up & a very luminous discharge occurs. The mercury which is partly dispersed in drops & partly volatalized is collected within the chamber & conducted to a reservoir below & this is done without any derangement of the place of discharge so that that important point is perfectly obtained and (when the apparatus is in order) without any issue of the mercury from the lamp into the outer space. The light differs much in character from that between carbon points, being as compared even to white or sun light very feeble in the red rays[.] Nevertheless it is a very beautiful light and not the less luminous or powerful because of its peculiar colour.

The nature of the lamp includes the following points in respect of its service and management in the lanthorn of a light house. It requires an adjustment of the force of the battery to the stream of mercury in the lamp a certain stream requiring for its best effect a certain battery force & vice versa - As the battery by continued action, falls in power, I conclude it will require adjustment - I understand the battery will last four hours and then requires a change - The lamp is externally a small thin glass cylinder fitted with iron ends & joining it may by time & use perhaps permit the accidental escape of mercury into the lanthorn - The glass itself may be broken by the heat within (as lamp glasses are) or by mechanical accidents - and such an event would derange the whole adjustment & throw the lamp out of service - The replacement of one lamp by another could not be instantaneous (like the Magneto electric lamp) but would take time & be rather complicated for a lighthouse keeper - The person or persons in charge of the lamp must have a thorough knowledge of the conditions necessary for its maximum action & of the nature & construction of the lamp & also of the associated Voltaic battery & its connexions[.]

With respect to the considerations which arise regarding the battery itself & the necessity of a place for it & its materials & a staff for its care & repair, I may refer generally to the like considerations at the end of my report on Dr. Watsons Electric light, 14 Aug 1854, and others about the middle of my report on Profr. Holmes Magneto electric light 29th April 1859³.

I do not know whether the author of the lamp proposes its trial in a lighthouse or whether he is aware what the Trinity house would require in that case[.] On a former occasion I stated that a light was required - Sufficient in intensity - Equal at different periods - Of uninterrupted continuance for 16 hours - Certain in its management by ordinary hands - Not dependent on processes or Machinery liable to occasional failure and especially not to sudden failure - Not dependent on arrangements requiring much room or much attention. The Trinity house requires a perfected application and an estimate of the outlay & the current expense for a given amount of light - for it cannot undertake to develop or perfect any principle & it cannot introduce any imperfect or uncertain arrangement into the lighthouse or any which it has not previously witnessed in action to the fullest extent⁴[.]

M. Faraday