74 Intelligence and Miscellaneous Articles. 



"O 



their angles with perfect accuracy : neither were the results, from 

 numerous cleavage-planes, uniform enough for this purpose ; although 

 in the latter case the reflective goniometer was used with the utmost 

 convenience. The inclination of the primary planes may be regarded 

 as an approximation to 121° and 59°, and those of the secondary 

 (intersecting the base parallel to its greater diagonal ) to the primary 

 146°. With the cleavage-crystals the following angles were ob- 

 tained, 120°, 121°, and 122°; a diversity very remarkable, as the 

 cleavages appeared to the eye quite perfect, and the planes highly 

 uniform. 



The cleavage parallel to the lateral planes is effected without much 

 difficulty, whilst no terminal one is visible j it breaking in that direc- 

 tion with great difficulty, and presenting an uneven and sub-hackly 

 fracture. The external planes of the crystals before being broken, 

 were dull and nearly black, owing to a thin coating of brown oxide 

 of iron ; but fresh cleavages presented a fine metallic lustre, and a 

 colour between silver-white and steel-gray. It breaks with the greatest 

 difficulty, and small masses often flatten under the blow of the ham- 

 mer, like pure iron. Its hardness is almost that of ordinary steel. 

 Specific gravity, in distilled water at 60° F., 7*337. It is highly mag- 

 netic, with polarity so distinct as to take up iron filings. Before the 

 blowpipe it melts. 



Fragments of the size of a pea, brought within the exterior flame 

 of the compound blowpipe, emitted a very slight vapour, in which 

 the well-known odour of arsenic was detected : and immediately on 

 coming within the inner cone of flame, they burnt with intense 

 energy, and with a most brilliant light, throwing out a profusion of 

 scintillations, after the manner of pure iron, or more like a burning 

 watch-spring. No odour of sulphur was perceived in these trials. 

 In order, however, to make myself sure of the absence of sulphur, I 

 resorted to the following experiment. A portion of the metal was 

 dissolved in dilute nitric acid : the solution was supersaturated with 

 potash and boiled in the alkaline liquor ; the precipitate was sepa- 

 rated, and the supernatant fluid neutralized by nitric acid, to which 

 was afterwards added nitrate of lead ; the precipitate was separated, 

 and found to be perfectly soluble in dilute nitric acid, thus evincing 

 the absence of sulphate of lead, which must have formed part of the 

 precipitate, provided sulphur had existed in the mineral under ex- 

 amination. 



After having examined it in the usual modes, for silver, gold, and 

 other metals, and not discovering any to be present*, I dissolved 

 fifty grains in nitric acid, with a view to ascertain merely the pro- 

 portion of iron present. After the solution appeared to be effected, 

 I observed a number of little black flakes floating in the liquid, which 

 resisted the action of the acid. These being separated by the filter, 

 were examined and found to be plumbago, which, under somewhat 



* After the iron had all been removed from the nitric solution by am- 

 monia, and the fluid boiled, hydro-sulphuret of ammonia gave no cloudi- 

 ness, thus evincing the absence of nickel. 



similar 



