23^ Scientific Intelligence. [Sept. 



fibrous and fasciculated. Specific gravity 2*987. Fusible before the 

 blowpipe into an opaque greenish enamel. It contains 



Silica 56-333 



Magnesia ^ S't'OOO 



Lime 10-666 



Protoxide of iron 4*300 



Alumina 1 666 



Water. .., 1*033 



Protoxide of chrome . . * A trace 



97-998 

 Loss , 2-002 



100-000 



'the loss of weight by ignition is estimated as water in this statement. 

 —(Silliman's Journal, vol. vi. p. 331.) 



VI. Discovery of Mineral Caoutchouc in Nexo Englandy United States, 



The following is Prof. Silliman's account of this discovery, as given 

 in hisiournal, vi. 370: — 



'* This remarkable mineral, hitherto nearly or quite confined to the 

 Odin mine at Castleton, in Derbyshire, has been recently found at 

 Southbury, 20 miles north-west of New-Haven. This region is a se- 

 condary trap basin, and although only six or eight miles in diameter, 

 it presents all the characteristics of the great trap region of Connecti- 

 cut and Massachusetts described by Mr. Hitchcock. Among other 

 things, it contains slaty rocks with bituminous minerals ; these have 

 induced a search for coal which is now going on. We understand that 

 they find bituminous slate or shale with small veins of coal. Specimens 

 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 or more in length ; they are 

 often cracked in the direction of the fibres, and between them there 

 are veins occupied by the mineral caoutcliouc. It has but little elasti- 

 city, 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 

 resinous and splendent lustre, and a flat ccnchoidal fracture ; it burns 

 with extreme brilliancy, with much black smoke, and an odour between 

 that of a bitumen and that of an aromatic ; 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 

 precisely 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 mineral are about one-quarter 

 nf an inch wide, and several inches long." 



VII. On an Improvement in the Apparatus for procurinrr Potassium. 

 By W. Mandell, BD. Fellow of Queen's College, Cambridge. 



** On repeating the late Prof Tennant's experiment for procuririg 

 potassium (which differs from the similar one first made by the French 

 chemists, Gay-Lussac, and Thenard, principally in being more simple 



