781 



The position of the crystal in the magnetic field is aflfected by the 

 approximation of extra magnets, or of soft iron ; but the author does 

 not beheve that this results from any attractive or repulsive force 

 exerted on the bismuth, but only from the disturbance of the lines of 

 force or resultants of magnetic action, by which they acquire as it 

 were new directions ; and, as the law of action which he gives, is, tbat 

 the line or axis of magnecrystallic force tends to place itself parallel, 

 or as a tangent, to the magnetic curve or line of magnetic force, passing 

 through the place where the crystal is situated, so the crystal changes 

 its position with any change of direction in these lines. 



A common horse-shoe magnet exhibits these phenomena very well : 

 the author worked much with one lifting 301bs. by the keeper; but 

 one that can raise a pound or two only, is sufficient for many of 

 the actions. When using the electro-magnet, the advantage of 

 employing poles with large plane opposed faces is mentioned as 

 being considerable, for then diamagnetic phenomena are almost 

 or entirely avoided and the peculiar magnecrystallic relations then 

 appear. 



The peculiar force exerted in these phenomena is not either at- 

 tractive or repulsive, but has for its distinctive character the ten- 

 dency to place the crystal in a definite position or direction. The 

 author further distinguishes it from that described by IvI. Pliicker in 

 his interesting memoir upon the repulsion of the optic axes of cry- 

 stals by the poles of a magnet*, in that, that is an equatorial force, 

 whereas this is an axial force. 



Crystals of antimony were then submitted to a similar magnetic 

 examination, and with the same results. But there were also certain 

 other effects produced of arrest and revulsion, the same in kind as 

 those described in a former series of the 'Experimental Researches' 

 (par. 2-309, &c.) ; these are WTOUght out and ehminated, and the re- 

 sults described. 



Arsenic also proved to be a body capable of pointing in the mag- 

 netic field, like bismuth and antimony. 



The paper describing the foregoing results is dated 23rd of Sep- 

 tember, 1848. In a later paper of the date of 20th October, 1848, 

 the author continues his researches. Native crystals of iridium and 

 osmium, and also crystallized titanium and tellurium, appeared to be 

 magnecrystallic : crj^stals of zinc, copper, tin, lead, gold, gave no 

 signs of this condition. Crysta,ls of sulphate of iron are very strongly 

 affected by the magnet according to this new condition, and the 

 magnecrystallic axis is perpendicular to two of the planes of the 

 rhomboidal prism ; so that when a long crystal is employed, it will 

 not, as a mass, point between the poles, but across the line joining 

 them. On the other hand, the sulphate of nickel has its magne- 

 cr}' stallic axis parallel, or nearly so, to the length of the ordinary 

 prism. Hence bodies, both magnetic and diamagnetic, are, by their 

 crystalline condition, subject to the magnetic force, according to the 

 law already laid down. Diamond, rock-salt, fluorspar, boracite, red 



* Poggendorff's Annalen, Ixxii. Oct. 1847 ; or Taylor's Scientific Me- 

 ::noirs, vol. v. p. 353. 



