James Timmins Chance to Faraday   22 April 1861

Hamstead, Birmingham | 22 April 1861

My dear Sir

Last week a new kind of lamp intended by me for the South Lighthouse at Whitby, was inspected at the Trinity House¹.

Mr. Masselin² who was present at the inspection has reported to me certain facts concerning the proportionate quantity of oil consumed in the lamp in comparison with others tried at the same time which seem to throw great doubt upon the propriety of measuring the performance of lamps by the consumption of oil apart from other considerations. As you have taken great interest in these matters you will excuse my writing to you upon the subject.- Now, according to Mr. Masselin’s statement the flame of the new lamp was by no means inferior to that of the others; & yet its consumption of oil in a given time was by far the least. The new lamp admits of producing an immense overflow, 1st because any degree of regular pressure is practicable & 2dly Because each of the Concentric wicks is separately supplied with oil.- Now Mr. Masselin & myself consider that this excessive overflow prevents a great evaporation of non-luminous gas from the oil, whereas that waste by evaporation occurs in lamps where the overflow is not sufficient-. The waste of oil in this case would be similar to the waste of fuel in furnaces, from which smoke is emitted. Whatever, however, may be the theory; the facts (wh: I believe that Mr. Masselin cannot have erroneously observed) suggest further investigation, before the consumption of oil is allowed to be taken as a measure of the due performance of a lamp.-

Yours very truly | James T. Chance

Professor Faraday.-

Endorsement: 22 April 1861 | To Prof: Faraday | Consumption of oil in a Lamp, not a measure of its due performance.