KECENT PROGRESS IN PHYSICS. 407 



liquids no adherent deposits could be produced even with the use of 

 separate decomposing cells. 



In conclusion, it may also be mentioned that the attempt has heen 

 made to gild silken threads and tissues without diminishing the flexi- 

 bility and strength of the goods ; the Prussian Geiverbe Ferein has 

 offered a premium for such a process, but, as far as I know, no one has 

 yet been successful. 



§ 183. Etching by galvanism. — It seems that Spencer first took up 

 this idea ; he procured a patent for his process in August, 1840. The 

 plate to be etched served as the anode, and was placed in a cell sepa- 

 rated by a porous diaphragm from the opposite copper plate. With 

 the copper plate acting as the kathode, sulphate of copper was always 

 used, but with the plate to be etched different liquids were employed 

 according to the nature of the metal. — (Dingler's Journal, vol. 80.) 

 For copper dilute sulphuric acid was employed, but it does not seem 

 that this process was ever found practically useful, since, according to 

 Hasse, (Dingler's Journal, vol. 84, from the Verhandlungen des Ve- 

 reins fiir Beforderung des Gewerbfleisses in Preussen, 1841, 5,) the 

 etching always proceeds more rapidly towards the border than in the 

 middle, and the same difliculty also occurs around such places as had 

 been stopped out after having been etched deep enough. Grove 

 (Dingler's Journal, vol. 82, from Philosophical Magazine, September, 

 1841) etched daguerreotype plates in the following manner: He used 

 one of his elements with plates of the same size as that to be etched, 

 placed the latter in a wooden frame, at a distance of 0,2 inches from a 

 Smee's platinized platinum plate, and immersed it for 20 to 30 seconds 

 in dilute muriatic acid, the connection with the element having been, 

 previously made. The daguerreotype plate was previously varnished 

 with shellac around its border and on the back, and after the etching 

 was carefully washed with aqua ammonia by means of a little pad of 

 cotton, then well rinsed in pure water and dried. Although the finest 

 lines had disappeared, still the plate gave good impressions. Grove 

 thinks it especially adapted for taking electrotype copies which may 

 be used for printing. 



About the same time Steinheil, in Munich, and Fizeau, in Paris, also 

 made attempts to etch daguerreotype plates. Fizeau's plates bore 30 

 to 40 impressions. 



§ 184. NohiU's rings. — Nobili's experiments are older than the period 

 to which my report is limited, and some of them date back as far as 

 the year 182G. He experimented with many liquids, and upon plates 

 of very different metals at the positive as well as at the negative pole. 

 An account of these experiments is to be found in Pogg. Ann., vol. 

 10, and also in Dingler's Journal, vol. 94. 



Nobili obtained the most brilliant colors from acetate of lead by 

 placing the metallic plate at the positive pole and immersing the 

 negative pole in liquid liquid. It is said that he also succeeded in pro- 

 ducing mono-chromatic coatings, but that he never communicated the 

 process to any one. BiJttger obtained such coatings upon platinum from 

 different })roto salts of manganese (hippurates, acetates, succinates.) 

 The platinum plate connected with the positive pole was laid in the 

 jgolution, and the negative pole, which was also a circular plate, was 



