Faraday to Jacob Herbert   1 February 1856

Royal Institution | Feby 1. 1856

Sir

In returning the letters from Ireland & France and according to your request¹ accompanying them by such observations as they may suggest I can only say that nothing of a negative character occurs to my mind:- the principles & object of both are good; of the practice of either you will not expect me to give an opinion.

In carrying out the principle I agree entirely with the French letter, in recommending that the light should be refracted & sent if possible at once in its right direction & not to have to pass through a second set of prismatic lenses; since in the latter case much of it must be lost. Even if the expence of both methods had been the same there would still remain this preservation of light for the French plan as well as greater final simplicity in the state of the apparatus[.]

Though I do not pretend to judge of the proper duration of a flash, still in observing that given by a revolving dioptric light apparatus I have often thought that it came on & passed away very suddenly & therefore the plan referred to in the French letter of making the Crown flashes preceed [sic] by 4° those of the under lenses commends itself to my mind².

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

Jacob Herbert Esq | &c &c &c