320 Intelligence and Miscellaneous Articles, 



ON A NEW GALVANIC PILE^ OF ECONOMIC CONSTRUCTION. 

 BY M. GAIFFE. 



The high price of galvanic piles and the difficulty of procuring 

 them being often an obstacle to the applications which might be 

 made of them, I essayed the possibility of devising an apparatus that 

 one could make anywhere without the aid of the professional work- 

 man, with substances of little value, widely spread in commerce, and 

 possessing the essential quality of constancy in the effects. 



The pair which, after some trials, I have adopted, resembles Cal- 

 laud's in its form, used some years since on telegraphic lines ; but 

 its elements are different. It consists of a vessel into which dip two 

 rods- — one of lead, the other of zinc. The leaden one descends to 

 the bottom ; the zinc is one half shorter. The bottom of the vessel 

 is coated with red oxide of lead (minium) ; and the exciting liquid 

 is water containing 10 per cent, of chlorhydrate of ammonia. 



The electromotive force of this pile is about one third of that of 

 a Bunsen's pair ; its internal resistance is slight, and varies little ; 

 the chloride of zinc formed does not sensibly alter the conductivity 

 of the exciting liquid ; its constancy is great ; finally the expense is 

 almost nothing when the circuit is open. — Comjptes Rendus de V Acad. 

 des Sciences, July 15, 1872, p. 120. 



" ACOUSTICAL EXPERIMENTS '^ ETC. 



To the Editors of the Philosophical Magazine and Journal. 



Stevens Institute of Technology, 

 Hoboken, New Jersey, U.S.A., 

 Gentlemen, August 15, 18/2. 



Will you have the kindness to publish the following as a substi- 

 tute for the erroneous paragraph which terminates my paper on 

 •* Acoustical Experiments &c." which appeared in the Philosophical 

 Magazine, April 1872.? 



Very respectfully, 



Your obedient Servant, 



Alfred M. Mayer. 



We will now examine the analogical phenomena in the case of 

 light. Let fork No. 1, giving 25 G vibrations in a second, stand 

 for 508,730,000,000,000 vibrations a second; which will be the 

 number of vibrations made by the ray D^ of the spectrum, if we 

 adopt 300,000 kilometres per second as the velocity of light. Then 

 fork No. 3 will represent 504,750,000,000,000 vibrations per second ; 

 which latter give a wave-length -0000048 millimetre longer than 

 that of Dp and belongs to a ray removed from D^ towards the red 

 end of the spectrum by eight times the distance which separates D^ 

 from D^. We saw that fork No. 3, giving 254 vibrations a second, 

 had to move towards the ear with a velocity of 8*734 feet to give 

 the note produced by 256 vibrations per second emanating from a 

 fixed fork ; so if a star which only sends forth those rays which vi- 

 brate 504,750,000,000,000 times a second were moving to\vards the 

 eye with a velocity of 2442 kilometres, or 1517 miles, its colour 

 would change to that given when D^ emanates from a stationary 

 soda-flame. 



I 



