The Annals of Philosophy (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1814 Excerpt: ...vary i3 size, rom a pin ea to a aze nut. ' ese no es are mixe with angular fragments of jasper, hornstone, and quartz. No fragments of corundum were visible; though, it is said, they now and then occur in some of the beds containing diamonds. From the above description there can be little doubt that the rock in qtpestion is anT: Lmygdaloid bslolnging to thg nlewelst floetz tra ormation. ou h the no u es are not a so ute identical pwith those which gccur in the amygdaloid of thi); country, yet they very nearly agree with it. From Dr. Heyne's description, it would alplpear that though this amygdaloidal rock is 0 some considera e thickness, yet the diamonds are confined to a bed in the centre of it, not more than a foot thick. This bed is distinguished from the rest of the rock by being harder. IV. Carlzonate of Iron. It has been known for some time to mineralogists that the substance called sparry iron ore, and jlos ferri, is a com ound of black oxide of iron and carbonic acid, or a carbonate of iron; and Dr. Wollaston has shown that it crystallizes in a form difi'ering a little from that of the pi-iinitive crystal of calcareous spar. It has lately been determined, by the chemical analysis of Descotils, and several other chemists, that the species known by the name of clay iron-stone, and so much employed in this country as an iron ore, is in fact a carbonate if iron likewise, and differs in nothing from sparry iron ore, except in not being crystallized, and in being mechanically mixed with some silicious matter and some manganese. Alumina is usually present only in a very small proportion, and seems to be in combination wit the silica; though in some specimens the proportion of alumina is considerable. The following is the result of an analysis of ...