Voltaic Process for Etching Daguerreotype Plates. 247 



table obtained by these means, for which the author expressed him- 

 self as indebted to Mons. C. de Rheims of Calais. 



4th. " Methods of giving more force and stability to the Currents 

 of Galvanic Batteries formed by a single Liquid." By Professor 

 Poggendorff. (Translation.) 



The copper plates of batteries are submitted to one of four pro- 

 cesses, which gives them a surface analogous to that of Mr. Smee's 

 platinized platinum. One of the methods is to deposit copper on 

 them by electrolysis. The action of such plates in combination with 

 amalgamated zinc is both powerful and constant. 



5th. " On a Voltaic Process for Etching Daguerreotype Plates." 

 By W. R. Grove, Esq., M.A., F.R.S., Prof. Exp. Phil. Lond. Inst. 



This discovery enables us to multiply in a durable material the 

 fleeting and delicate traces of Daguerreotype. The plate to be etched 

 is made a positive electrode, in an electrolyte of dilute hydrochloric 

 acid ; and the action is continued for a few seconds. The etchings 

 are fit for the printer. Several prints obtained from plates thus pre- 

 pared were placed before the Society, and were much admired as 

 specimens of what may be done when the art has been further carried 

 out. The author states that these prints are not so true to nature 

 as the original picture, because in order to etch deep enough to re- 

 ceive the j>rinting ink, some of the fine lines will blend. This will 

 not practically be an objection to the process, because no lines are 

 lost except those which, if present, could not be appreciated. One 

 very important application of the art is to etch very delicately a 

 picture, and to take from this perfect etching electrotype copies. 

 These are so true that the author actually read on one, by micro- 

 scopic aid, five lines of inscription on a surface l-10thby 6-100dths 

 of an inch. The following are the concluding words of this com- 

 munication : — " I transmit with this paper some specimens of en- 

 gravings of the etched plates, and of electrotypes taken from them ; 

 and in conclusion would call attention to the remarkable instance 

 which these offer of the effects of the imponderable upon the pon- 

 derable. Thus, instead of a plate being inscribed as ' drawn by Land- 

 seer and engraved by Cousins,' it would be ' drawn by Light and 

 engraved by Electricity.' " 



The business of the evening terminated by the reading of Mr. 

 Weekes's Monthly Journal of the electric state of the atmosphere. 



ROYAL IRISH ACADEMY. 



Abstract of Observations on the Origin of Audible Sounds. By 

 Robert Kane, M.D.* 



Nov. 30, 1840. — Dr. Kane read a paper " On the Production of 

 Audible Sounds," of which the following is an abstract. 



The sensation of sound is produced upon the ear by the tym- 

 panum being thrown into vibratory motion, isochronous with the 

 vibrations transmitted from the sounding body. 



* From the Proceedings of* the Royal Irish Academy. 



