SS8 Prof. Johnston 07i Hatchetine, 



that the larger calculus was taken from the bladder of a 

 young man after death, who during life had exhibited no 

 symptoms of any affection of the urinary organs. 



Should this meet with your approval, its insertion in your 

 ensuing Number will much oblige. 



Gentlemen, yours, &c., 

 March 13, 1838. Thomas Taylor, 



New Bridge Street, Blackfriars. M.R.C.S. 



LV. On the Composition of certain Mineral Substances of Or- 

 ganic Origin, By James F. W.Johnston, M.A., F.R.SS., 

 L, and £., F. G.S., Professor of Chemist?'!/ and Mineralogy, 

 Durham*. 



II. Hatchetine, 

 T^HIS mineral is known to occur, though rarely, in con- 

 -*- nection with the iron ores of the coal measures in Gla- 

 morganshire, and in some of the Midland counties of England. 

 The specimen to which the following description and analysis 

 applies was from the former locality,' and I have been in- 

 debted for it to the liberality and kindness of Sir David 

 Brewster. 



It is transparent, yellowish, consists of thin laminae of a 

 nacreous lustre, has the consistence of soft wax, is greasy to 

 the touch; at ordinary temperatures has no perceptible smell, 

 but when heated emits a fatty odour. Its specific gravity at 

 60° Fahr. is 0-916, and it melts at about 1 15° Fahr. I am in 

 possession of too small a quantity to enable me to ascertain 

 its boiling point. By a cautious application of heat it appears 

 to distil over without change. 



Exposed to the air for a length of time it blackens on the 

 surface, and becomes opake, and it is found in most cabinets 

 in this state. When melted, the black particles, probably 

 charcoal from the slow decomposition of the mineral, float in 

 the fluid and exhibit much lustre. 



Boiling alcohol dissolves it very sparingly, and from the so- 

 lution it is nearly all precipitated on cooling, ^ther in the 

 cold also dissolves a very small quantity ; in boiling sether 

 it is more largely soluble. On cooling, the solution coagulates 

 into a mass of minute fibres (prisms), from which the aether 

 may be separated by agitation or compression, and which 

 have a crystalline nacreous lustre. In recent specimens the 

 mineral is said sometimes to occur in large crystals, with the 

 form of which I am unacquainted. After repeated boiling 

 with aether there remains still a minute portion undissolved, 



• Communicated by the Author- 



