Faraday to Peter Henry Berthon   21 February 1857

Royal Institution | Albemarle St. W. | 21 February 1857

Sir

In reply to your letter of the 19th¹ I have to state that I have never had the qualities of either Spermaceti or Rape oil in regard to the particular fitness of different specimens for combustion in lamps brought before me nor am I aware that there is any ready process for distinguishing their qualities. I have always understood that the ability to distinguish better from worse has depended upon the experience of the parties judging & their acquaintance with the run of qualities. I have not any judgment in that matter myself²[.]

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

P.H. Berthon Esq | &c &c &c