1824.] New Scientific Books. 317 



15. Electromagnetic a?id Galvanic Experiments. By Dr. Hare. 



If a jet of mercury, in communication with one pole of a very 

 large calorimotor, is made to fall on the poles of a very large 

 horse-shoe magnet communicating with the other, the metallic 

 stream will be curved outwards or inwards, accordingly as one 

 or the other side of the magnet may be exposed to the jet, or 

 as the pole communicating with the mercury may be positive or 

 negative. When the jet of mercury is made to fall just within 

 the interstice formed by a series of horse-shoe magnets, 

 mounted in the usual way, the stream will be bent in the direc- 

 tion of the interstice, and inwards or outwards, according as 

 the sides of the magnet, or the communication with the galvanic 

 poles, may be exchanged. The result is analogous to those 

 obtained by Messrs. Barlow and Marsh with wires, or wheels. 



It is well known that a galvanic pair, which will, on immer- 

 sion in an acid, intensely ignite a wire connecting the zinc and 

 copper surfaces, will cease to do so after the acid has acted on 

 the pair for some moments, and that ignition cannot be repro- 

 duced by the same apparatus, without a temporary removal from 

 the exciting fluid. 



I have ascertained that this recovery of the igniting power 

 does not take place, if, during the removal from the acid, the 

 galvanic surfaces be surrounded either by hydrogen gas, nitric 

 oxide gas, or carbonic acid gas. When surrounded by chlorine, 

 or by oxygen gas, the surfaces regain their igniting power in 

 nearly the same time as when exposed to the air. 



The magnetic needle is nevertheless much more powerfully 

 affected by the galvanic circuit, when the plates have been 

 allowed repose, whether it take place in the air, or in any of the 

 other gases above mentioned. — (American Journal of Science.) 



Article XVIII. 

 NEW SCIENTIFIC BOOKS. 



PREPARING FOR PUBLICATION. 



A Translation of the Travels of the Prussian General Baron Minu- 

 toli, in Lybia and Upper Egypt ; illustrated with Maps and Plates. 



The First Volume of the Lectures of Sir Astley Cooper, Bart, on 

 thePrinciples and Practice of Surgery, as delivered at St. Thomas's and 

 Guy's Hospitals. With additional Notes and Cases, by Frederick 

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A Practical Treatise on Prisons, and an Inquiry into the Duties 

 and Perplexities of Medical Men as Witnesses in Courts of Justice. 

 By Dr. J. G. Smith. 



