1821.] Scientific Intelligence. 151 



alternating, but not with apparent regularity. The pure copper and 

 red oxide are sometimes intermixed in the same layer. 



The red oxide is distinctly, though minutely, crystallized in the form' 

 of the primary octohedron, and of the cube, and in intermediate 

 varieties. 



The pure copper is also in extremely small and brilliant crystals, but 

 so minute that I cannot perceive their forms by the help even of the 

 strongest glass. 



The greater part of the surface of the mass is tinged of a green 

 colour ; portions of it are vitreous and transparent. The green 

 colour is found, by the assistance of a strong glass, to be owing to the 

 presence of fibrous crystals which are translucent, but too minute for 

 the determination of their form. They have greatly the colour and 

 appearance of the phosphate of lead — Ed. 



II. Description of Two New Mineral SuhstanceSy found hy Dr, Mac» 

 culloch in Rum and Mull, 



" The last mineral substance," says Dr. Macculloch, " which re- 

 mains to be enumerated, being hitherto undescribed, it is necessary 

 to enter into a minuter detail respecting it. Many years have passed 

 since I discovered it both here (Rum) and in Fife ; and the description 

 has been hitherto delayed in hopes of finding larger specimens, better 

 adapted for elucidating its history. These hopes have been hitherto 

 disappointed, and I must therefore give it, however imperfect ; in 

 hopes that other mineralogists will hereafter supply the deficiencies. 

 When recently broken it is of a green colour ; varying from the transr 

 parent yellow green of the finest olivin (or chrysolite) which it some- 

 times resembles so as to be undistinguishable, to the dull muddy green 

 of steatite, to which in this case it bears an equal resemblance. In a 

 few hours after being taken from its repository, or exposed to the air, 

 it turns darker, and shortly becomes black ; a change which also occurs 

 within the rock at the depth of an inch or more from the surface. In 

 this case, the transparent variety puts on the external aspect with the 

 histre of jet : while the opake one preserves its dull surface, and more 

 nearly resembles black chalk. Notwithstanding this change, the 

 mineral when in small fragments still continues to transmit light. The 

 first variety remains perfectly translucent, and presents in some spe- 

 cimens the fine brown orange of cinnamon stone, in others a rich bottle 

 or olive green. The other appears also of an olive green, but it is not 

 more translucent than ore of the same thickness. When powdered, 

 the one is of a snuffy brown, the other of a dirty olive. The structure 

 of the first variety is generally conchoidal, that of the second is com- 

 monly intermediate between the conchoidal and granular. It is so 

 soft as to be scratched by a quill, and is brittle ; easily breaking into 

 minute irregular fragments. The specific gravity is 2-020. With 

 respect to its chemical habits, it remains unchanged before the blow- 

 pipe ; neither cracking nor sensibly altering its colour or translucency. 

 It is apparently as refractory as quartz ; a remarkable circumstance, 

 when the quantity of iron in it is considered. It is acted on by muriatic 

 acid, giving indications of a considerable proportion of iron, with a 

 little alumina; but the principal constituent appears to be silica. There 

 are no traces of lime or of manganese. The very minute quantity I 



