1821.] New Scientific Books. 397 



loses its magnetism by being struck when in the plane of the magnetic 

 equator. 



11. An electrical discharge, made to pass through a bar of iron, 

 devoid of magnetism, when nearly in the position of the magnetic 

 axis, renders the bar magnetic ; the upper end becoming a south pole, 

 and the lower end a north pole; but the discharge does not produce 

 any polarity, if the iron be placed in the plane of the magnetic equa- 

 tor. Tile effects appear to be the same, whether the discharge be made 

 on the lower or upper end of the bar, or whether it is passed longitu- 

 dinally or transversely through the iron. 



12. A bar of iron possessing some magnetism has its polarity dimi- 

 nished, destroyed, or inverted, ifan electric discharge be passed through 

 it, when it is nearly in the position of the magnetic axis, provided the 

 south pole of the bar be downward, while its magnetism is weakened, 

 or destroyed, if it receive the shock when in the plane of the magnetic 

 equator. 



13. Iron is rendered magnetical, if a stream of the electric fluid be 

 passed through it, when it is in a position nearly corresponding with 

 that of the magnetic axis ; but no effect is produced, when the iron is in 

 the plane of the magnetic equator. — (Edinburgh PhilosophicalJournal.) 



V. Dissection of Crystals, 



M. Faraday found, that those specimens of sulphuret of antimony 

 which are crystallized in large crystals, crossing each other, admirably 

 illustrate iMr. Daniell's mode of displaying crystalline texture by dis- 

 section. On introducing such a piece of sulphuret into a portion of 

 fused sulphuret, and continuing the heat, it begins to melt down ; but 

 so far from this taking place uniformly at the surface, crystals will 

 sometimes be left more than half an inch long projecting from it; and 

 in other places, the cavities left by fused crystals will be so large, and 

 have such perfect surfaces, that the angles they form with each other 

 may be readily ascertained. In order to observe these effects, it is 

 only necessary to remove the half fused piece of sulphuret from its hot 

 bath, and allow it to cool. — (Institution Journal.) 



Article XIV. 

 NEW SCIENTIFIC BOOKS 



PREPARING FOR PUBLICATION , 



Mr. Swalnsonis preparing for publication, Exotic Conchology, a 

 Work to consist of coloured Plates of rare and nondescript Shells. 



A General History of Birds, by J. Latham, MD. &c. Author of the 

 Synopsis of Birds, &c. 



The Fossils of the South Downs ; or Outlines of the Geology of the 

 South Eastern Division of Sussex, by Gideon Mantell, FLS. 



JUST PUBLISHED. 



A Manual of the Diseases of the Human Eye, from the best National 

 and Foreign Works ; translated from the German of Dr. Weller, and 



