88 



THE GEOLOGIST. 



Erratum. — In my last article, in lieu of the Dote at foot of page 34, 

 read, — " Most of the alum thus produced is no doubt iron-alum, i.e. it 

 contains sulphate of iron, and no alumina.'' Sulphate of peroxide of 

 iron and sulphate of alumina, being isomorphous salts, can replace 

 one another in their combinations without causing a change in the 

 crystalline form of the product. Thus, if these two salts be dissolved, 

 they cannot be separated by crystallization : every crystal will contain 

 both. This is often a cause of great inconvenience ; for, when 

 common alum (sulphate of potash and alumina) be mixed with, or 

 replaced by, iron-alum (sulphate of potash and iron), it cannot be 

 employed in dyeing, calico-printing, &c. Now, this must be inevitably 

 the case with the alum produced by the spontaneous combustion of 

 the coal-beds of I'Aveyron, mentioned in our preceding article, from 

 the decomposition of the iron-pyrites. 



EEVIEWS. 



Siluria. The History of the Oldest Fossiliferous Rocks and their Foundations ; with 

 a Brief Sketch of the Distribution of Gold over the Earth. By Sir R. I. MuR- 

 CHisoN, &c. (Third Edition, including the " Silurian System.") With Maps 

 and many additional Illustrations. 1859. Svo. London : Murray. 



This long-expected book has at last appeared, and presents a result weU w^orthy 

 of the care and pains that have been evidently bestowed upon it ; and its handsome 

 appearance prevents regret for any delay in its production. The printers, mth 

 good paper, clear type excellently printed, and the skill they have displayed in 

 making the most of the numerous woodcuts with which it is illustrated, well 

 merit the passing word of praise which the reviewer is licensed to give them. 



The chief attraction of the new edition (we object to style it " the third," for 

 the greater and original work, the " Silurian System," must then be regarded as 

 the first) is in its matter. Designed as the book is to give us the histoiy of the 

 most remote periods of organic life upon our planet, eveiy new word of truth which 

 the author has elicited in the four years since he last revised his former labours — 

 from the thick and ponderous records of the wonderfid rock-masses and mountainous 

 regions of which the Silurian region offers the ty]:)es — will be looked for and sought 

 out with eager eyes and anxious expectation. As we look with intense interest 

 upon every trace of the first existence of our race upon this planet, and prize the 

 intrinsically worthless flint or stone beyond the cost of gold, because some unknown 

 human hand has chipped it into barbarous shape of arrow-head or axe, so with still 

 more wonder do we regard the rain-prints, the worm-tracks, and the creeping things 

 of that " long, long ago," when life first, as far as the traces of it have yet been dis- 

 tinctly observed, gave its gi-eat distinctive and marvellous feature to that world 

 which " was our cradle and which will be our grave," — the scene of all om- loves, 

 and hopes, and fears, our joys and sorrows, — linked to us by every tie of Mendship 

 and affection, and dear to us even in the days of soitow and of teai-s. 



It is something in such an active and intelligent world to attain eminence — to 

 reach that point from whence we can look back or do^vn — to be able to say we 

 have done good service, or that we have surpassed our fellows in the intellectual 

 race, — and so well establislied is the veteran eminence of Sir Roderick IMurchison 

 that we may acknowledge it witliout flattery or adulation ; but, like as the poorer 

 portion of humanity envy the good coat on every man's back they see, so there are 

 some sm flier minds even in scientific circles who W(mld attempt to detract from 

 the fame which a long, active, and useful life has fairly earned ; and we are glad 



