558 Reviews — Br. T. Sterry Hunt's Chemico- Geological Essays. 



In 1873 we find Dr. Sterry Hunt complaining that, in his endeavours 

 to reconstruct dynamical geology on a new basis since 1858, his views 

 have been appropriated without acknowledgment by Le Conte, 

 Mallet, and others. Le Conte, we are told, says that the whole theory 

 of igneous agencies must be reconstructed on the basis of a solid earth, 

 a view adopted, and ably defended, but not originally propounded, 

 by Hunt, who takes the opportunity of pointing out that his theory 

 of the plastic zone of sediments affords the necessary cushion be- 

 tween the outer crust and the rigid central mass. There are, it must 

 be admitted, instances when people appropriate the doctrines of 

 others, after having opposed something like them for years, and this 

 may occur both in the political and scientific world. But we must 

 also bear in mind that great ideas are epidemic, and that discoveries 

 have at times been announced almost simultaneously from different 

 quarters. The question of priority is often rather delicate, though 

 in one instance at least, as Professor Dana has admitted with 

 characteristic candour, Dr. Sterry Hunt's claims to priority were 

 incorrectly denied. 



History of the crystalline rocks. — This subject is so bound up on 

 the one hand with the questions already discussed, and on the other 

 with the geognosy of extensive areas both in the Old and New 

 World, that it may be regarded as a sort of connecting link between 

 the previous speculations and pure geology. Most of the former 

 questions are likely to remain open for some generations to come; 

 but in the history of the crystalline rocks we have more accessible 

 ground for discussion, and the subject is one in which geologists can 

 take an especial interest. Our author's general declaration of faith 

 has appeared so recently in this Magazine (Geol. Mag. for 1878, 

 p. 466), that a very brief epitome will meet the case, viz. that the 

 various " crystalline stratified rocks are not plutonic, but neptunean 

 in origin, and, except so far as they are mechanical sediments coming 

 from the chemical or mechanical disintegration of more ancient rock- 

 masses, were originally deposited as, for the most part, chemically 

 formed sediments or precipitates, in which the subsequent changes 

 have been simply molecular, or at most confined to reactions, in 

 certain cases, between the mingled elements of the sediments." He 

 claims that some of the most enlightened students now favour the 

 neptunean origin of rocks ; one of the most notable examples being 

 that of Delesse, at one time a pillar of the metamorphic school, who 

 has recently criticized the views of Von Lasaulx and Knop with 

 regard to wholesale metasomatic changes, which Delesse designates 

 as metamorphisme a Voutrance. Hunt further quotes Delesse as 

 objecting to the idea of orthoclase being connected on the one hand 

 with the volcanic mineral leucite — from which the transmutationists 

 would derive it — and on the other hand with potash-mica supposed 

 to be formed from the orthoclase. He challenges his reader to com- 

 pare the above citations from Delesse with his own language on the 

 doctrines of pseudomorphism by alteration as applied by some who 

 would maintain the possibility of converting almost any silicate into 

 any other (vide also p. 321 et seq.). Finally, at the close of the preface 



