370 Mineral Caoutckouc. 



6. Mineral Caoutchouc. 



This remarkable mineral, hitherto nearly or quite confined 

 to the Owdin mine at Castleton, in Derbyshire, has been re- 

 cently foLird at Southbury, twenty miles N. W. of New- 

 Haven. This region is a secondary trap basin (see Vol. II 

 pa. 231 of this Journal) and although only six or eight miles 

 in diameter, it presents all the characteristics of the gieat 

 trap region of Connecticut and Massachusetts described by 

 Mr. Hitchcock. Among other things, it contains slaty rocks 

 with bituminous minerals; these have induced a research 

 for coal which is now going on. We understand that thev 

 find bituminous slate or shale with small veins of coal. Spe- 

 cimens confirming this statement are now on the table, and 

 they exhibit fibrous limestone, forming very distinct veins, 

 or rather layers, running parallel with, and lying between 

 those of the slate. The fibres of the satin spar or fibrous 

 limestone, are one inch and more in length; they are often 

 cracked in the direction of the fibres and between them 

 there are veins occupied by the mineral caoutchouc. It 

 has but little elasticity, it is soft, easily impressible by the 

 nail, and compressible between the fingers like potassium, 

 and can be formed into a perfect ball ; its colour is jet 

 black; some varieties of it are a little harder, and have a re- 

 sinous and splendent lustre, and a flat conchoidal fracture ; 

 it burns with extreme brilliancy with much black smoke 

 and an odour between that of a bitumen and that of an aro- 

 matic; during the combustion, drops of liquid fire fall in a 

 stream, or in quick succession, and with a whizzing noise 

 exactly like the vegetable caoutchouc and it melts precise- 

 ly as that substance does. Rubbed on paper it leaves a 

 black streak and acquires a high polish, it does not remove 

 pencil marks from paper. The veins containing this min- 

 eral are about one quarter of an inch wide and several inch- 

 es long. — Ed. 



April 10, 1823. 



ted to describe the most dangerous fulminating preparations, lest his readers 

 should incur injury from attempting the experiments. There are a few ty- 

 pographical errors ; the most important which we observed is, that hydrogen 

 stands as the basis of nitric acid, (p. 21.) We do not observe any table of 

 errata. This little work cannot fail to be very useful in schools, and to pri- 

 vate experimenters, and contains a great deal in a small compass. 



