Excerpt from The Edinburgh New Philosophical Journal, Vol. 15: Exhibiting a View of the Progressive Discoveries and Improvements in the Sciences and the Arts, January April 1862 We find, on examination, that in many of these rocks, the ratio of the oxygen of the silica to that of the bases is as 3: 2, which corresponds to that of aluminous augite and of labra dorite, and of course also to any combination of the two. This is the ratio assigned by Bunsen to one principal division of the characteristic eruptive rocks of Iceland. We meet with rocks of this ratio in all parts of the Malvern Hills, and under various forms. Thus, in a fine-grained mixture of hornblende and epi dote in the North Hill in a red rock, with epidote and gold mica, further south (xiii) in a grayish black rock forming a vein in the syenite over west malvern (x.) in a similar rock from the railway tunnel, under the South Hill (xi.) in some of the peculiar traps of the West Ragged stone, and of the dykes at its base (xiv. The ratio of the oxygen of the silica to that of all the bases taken together is nearly as 3: 2. In other rocks, this ratio is as 3: 24, as we find it to be in some bosses of trap on the hill above Bransill Castle (xv. Xvi), and in the rocks of the large quarry between North Malvern and West Malvern (i.-iv.) And other rocks have an intermediate commition, so that we pass, by scarcely perceptible gradations, from one of these classes to the other; and this variation is found to prevail as much amongst those rocks which closely resemble each other in appearance as amongst those which are dissimilar. It should be observed that many of these rocks bear evidence of some alteration from their original composi tion: the quantity of water contained in them being large, and portions of their silica as well as of their bases being found deposited in their fissures and cavities. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.