132 Chronicles of Science. [Jm., 



its resemblance to muscular tissue. Koclielite occurs as a brownish- 

 yellow incrustation, with a columnar structure, uivesting titanic 

 iron-ore and fergusonite. Its analysis, wliicb is extremely complex, 

 points to its chemical relations with yttrotantalite. The second 

 mineral, Sarcopside, occurs in ellipsoidal masses invested with 

 vivianite and embedded in granite. Internally these nodules 

 exhibit a complicated structure, being made up of a reticulated 

 arrangement of thread-like crystals, varying in colour from 

 lavender to flesh-red. It is essentially a phosphate of iron and 

 manganese, its analysis leading to the following unattractive 

 formula : — 



3 PO5 (2 Fe 0, Mn 0) -f PO^ (2 Mn 0, Ca 0) + Fe Fl + Fe, O3, HO. 



For some years past extensive deposits of potash-salts have been 

 worked iii connection with the rock-salt of Stassfurt, in Prussian 

 Saxony. Among these potash-salts — so valued by the agriculturist 

 as fertilizing agents — the chloride of potassium in a compact state 

 has long been found, and has passed under the various names of 

 Leopoldite, Schiitzelhte, and Hovelite. Sijlvine is, however, the 

 mineralogical name by which the pure chloride is best distinguished. 

 Of this mineral some splendid crystals have lately been found lining 

 large drusy cavities in the Stassfm-t deposits. The crystals — of 

 which some of the faces measure a couple of inches across — are 

 combinations of the cube and octohedron, and exhibit a perfect 

 cubic cleavage. In appearance they strongly resemble rock-salt, 

 but are distinguished by a somewhat sharper taste. Although 

 usually colourless, they are sometimes tinged red, either by 

 mechanical enclosure of oxide of iron, or by the presence of a 

 gaseous substance, probably marsh-gas. The crystals are almost 

 pure potassium chloride, containing only a small jiercentage of the 

 chlorides of sodium and magnesium, with traces of the sulphates of 

 soda and magnesia. A notice of tlie mineral has been laid before 

 the German Geological Society by Herr Huyssen.* 



Avaihng himself of these crystals of sylvine — unparalleled as 

 they are for size and transparency — Professor IMagnus has been 

 enabled to examine the effect of chloride of potassium on radiant 

 heat.f He finds its behaviour to be precisely similar to that of 

 the analogous sodium compound ; both minerals being highly 

 diathermanous, irrespective of the temperature of tlie source of heat. 

 Sylvine is thus entitled to share the ajipellation liithcrto enjoyed 

 solely by rock-salt — that of " the glass of radiant heat." 



Mr. J. R. Gregory has just returned from a mineralogical tour 

 in South Afi-ica, having been commissioned by Mr. Harry Emanuel, 



* Zeitschr. d. deutsch. geolog. Gesellsoli. 1802. Heft II., p. 4G0. 

 t 'Comptes Reudus,' 1st Sum., No. 20, p. 1302; ' Pliil. Mag.,' Oct. 1868, 

 p. 320. 



