1 74 Miscellanies. 



r 



F 



the process being in every respect so different, we cannot see that it in 

 any way interferes with the position of Mr. Talbot. 



We must leave this question and now proceed to analyze the claims of 

 two of our countrymen, Messrs. Havell and Wellmore, who are said to have 

 introduced an important addition to the process pursued by Mr. Talbot, a 

 full description of which is contained in a letter to the editor of the Liter- 



ary Gazette. The first attempt of this gentleman was^irected towards an 



etching, by Rembrandt, of an old man reading, and the result was a rever- 

 sed fac-simile J a negro face surmounted by locks of silver; the disappoin- 

 ted artist discovered tliat a second transfer entirely destroyed the spirit of 

 the picture._^-To 



which this defect was indeed removed, but the great merit of the art, name- 

 ly, self-acting power, was lost, A thin plate of glass was laid on the subject 

 to be copied, upon which the high lights were painted with a mixture of 

 Avhite lead and copal varnish, the proportion of varnish being increased for 

 the darker shading of the picture. The next day Mr. Havell removed the 

 white ground with the point of a penknife, to represent the dark etched 

 lines of the original, and a sheet of prepared paper having been placed 

 behind the glass and thus exposed to the light, a tolerable impression was 

 produced; the half tints had, however, absorbed too much of the violet 

 ray, an imperfection which was remedied by painting the parts over with 

 black on the other side of the glass ; if allowed to remain too long exposed 

 to the sun's rays the middle tints became too dark, and destroyed the ef- 

 fect of the sketch; about ten minutes in a powerful sun was consid- 

 ered sufficient." Another method employed by Mr. Havell was to spread 

 a ground composed of white lead, sugar of lead, and copal varnish, over a 

 plate of glass, and having transferred a pencil drawing in the usual man- 

 ner, to work it out with the etching point till it bore the appearance of a spiri- 

 ted ink drawing, or in the hands of an engraver a highly finished engra- 

 ving.^ The above process Mr. Havell made public under the impression 

 that it had been hitherto overlooked, but Mr. Talbot, hearing that he was 

 about to apply for a patent, laid claim to the improvement as his own, and 

 not only pointed out some parts of his former memorial where it was dis- 

 tmctly mentioned, but also produced several drawings made precisely in 

 the manner described; he has also laid before the Royal Society a new 

 method of preparing the sensitive paper, which consists in immersing it 

 in a solution of nitrate of silver, and after washing it with bromide of po- 

 tassmni, the nitrate of silver is again applied, the preparation being 

 dried by the fire between each operation ; the paper thus treated is ex- 

 tremely sensitive, changing with the feeblest daylight, first to a bluish 

 green then to olive green, and finally to black. 



A letter to Mr. Talbot from his friend M. Biot has also been published, 

 and contains many interesting experiments. After commenting on the 

 value of the discovery, he continues—" The interest with which I viewed 



