2i Mr. Smith and Dr. Brett's Additional Remarks 



being inscribed, as " drawn by Landseer, and engraved by 

 Cousins," it would be " drawn by Light, and engraved by 

 Electricity !" 



London Institution, Saturday, Aug. 14, 1841. 



[With this communication were sent plates etched by the 

 process detailed in the text; electrotype copies from the 

 same ; and a considerable number of prints obtained from the 

 former. — Sec. Elect. Soc] 



Postscript by the Author, Nov. 1. — Few of the readers of the 

 Philosophical Magazine will have an opportunity of seeing 

 any specimens of the process, and as the etching is not deep 

 enough to jiroduce impressions sufficient to accompany the 

 paper, I may give an idea of them by saying that in the print 

 of a portrait which I have now before me the whole expres- 

 sion of the features is distinct, the pupil of the eye and the 

 speck of light upon it clearly defined, the gloss of the hair and of 

 the satin stock very accurate. The microscopic details alone 

 appear incapable of transference to 2^aper, but these, as stated 

 above, being absolutely perfect upon the etched plate, I had 

 intended to have directed some experiments to the substitu- 

 tion of more delicate materials than paper and printing-ink 

 for receiving the impressions ; incessant occupations have pre- 

 vented me, and will I fear for some time. 



I would suggest the employment of hyposulphite of soda 

 instead of ammonia to remove the oxvchloride. — W. R. G. 



VI. Additional Remarks on the alleged Conversion of Carbon 

 into Silicon. By J. Denham Smith, Esq. and R. H. 

 Brett, Ph. D. 



To Richard Phillips, Esq., F.R.S. 



Dear Sir, 

 T N Dr. Brown's observations, p. 389, pres. vol., he states, 

 -*■ " For the next experiments, on the ferrocyanide of potas- 

 sium, let such as are interested in the subject judge whether 

 they be sufficient repetitions ot mine. I may mention, in pass- 

 ing, that the two apparatus described in this part of your 

 Correspondents' letter, viz. an iron tube closed with an iron 

 plug, and a gun -barrel protected by luting and well secured 

 at the orifice, were the very instruments that foiled me last 

 November and December. There must be free enough exit 

 for nitrogen," &c. Now we may observe, that the iron tube 

 with an iron plug was the instrument chiefly employed by us 

 for the purpose of heating ferrocyanide of potassium and car- 

 bonate of potash together; nor did we employ this instrument 



