76 Royal Society. 



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 30lbs. 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 employ- 

 ing poles with large plane opposed faces is mentioned as being con- 

 siderable, 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 M. 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 wrought out and eliminated, 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 : crystals of zinc, copper, tin, lead, gold, gave no 

 signs of this condition. Crystals 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- 

 crystallic 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, fluor spar, boracite, red 

 oxide of copper, oxide of tin, cinnabar, galena, and many other 

 bodies, presented no evidence of the magnecrystallic condition. 



The author then enters upon a consideration of the nature of the 

 magnecrystallic force. In the first place he examines closely whe- 

 ther a crystal of bismuth has exactly the same amount of repulsion, 

 diamagnetic or other, when presenting its magnecrystallic axis 

 parallel or transverse to the lines of magnetic force acting on it. For 

 this purpose the crystal was suspended either from a torsion ba- 



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

 moirs, vol. V. p. 353. 



