Reviews — A. Daubree & Experimental Geology. 425 



phism lie expressly excludes the old gneisses and mica-schists which 

 underlie the stratified fossiliferous terranes, and confines his obser- 

 vations to the schistose masses whose metamorphic origin is, he says, 

 clearly demonstrated. 



This is certainly begging a question which many persons would 

 be by no means willing to concede. The above quoted remarks 

 were originally published by M. Daubree in 1859, and have not 

 been altered in the present work, so that no reference is made to the 

 numerous memoirs which have appeared since that date. It is clear 

 that M. Daubree still continues a strong believer in the doctrine of 

 Epigenesis — that Hibernian form of metamorphism which is accom- 

 panied by considerable change of substance. It somewhat detracts, 

 therefore, from the interest of this part of his work, that he has not 

 thought fit to notice the numerous papers contributed to this subject 

 of late years. We find him, for instance, stating that this modifica- 

 tion (regional metamorphism) is easily recognized in such countries 

 as Wales, the Taunus, and the Ardennes. Certainly the alleged 

 metamorphism of portions of the former country has been disputed 

 on good grounds by very competent observers, who, although they 

 probably differ in details, have adduced most excellent evidence that 

 certain beds of obscure origin are by no means the metamorphosed 

 equivalents of beds elsewhere recognized as forming part of sedi- 

 mentary formations of known age. We leave the Taunus and the 

 Ardennes to the consideration of foreign critics. 



In the Alps there seems to be better evidence of metamorphism 

 as understood by M. Daubree, but the strongest case is the well- 

 known one in the Vosges, where, as observed by M. Delesse, the 

 organic remains so well preserved at Rothau deserve to be con- 

 sidered as the classical monuments of metamorphism. Here syen- 

 itic granite has penetrated Devonian beds, which for several 

 hundred metres from the point of contact are entirely modified. 

 At certain points the altered rock consists of a compound of lamellar 

 pyroxene, epidote, and compact garnet, associated with abundance of 

 fossil corals. The cavities bristle with elongated crystals of amphi- 

 bole, etc. Such a case as this should in fairness be quoted under 

 the head of metamorphism of juxtaposition ; but anyhow it is a hard 

 nut for those who disbelieve in the extensive alteration of sedimen- 

 tary beds to crack. 



The causes of metamorphism are next considered, and here it is 

 again evident that change of substance as well as of form is the kind 

 of metamorphism most frequently present in the mind of the author. 

 Heat (which is from two sources), even when aided by certain 

 vapours, is not sufficient ; we must, then, look tq water as having 

 performed an important part " dans les phenomenes metamor- 

 phiques aussi bien que dans les eruptions des volcans." This 

 requires to be further supplemented by pressure. 



It became necessary, therefore, in the application of the experi- 

 mental method, to ascertain how far heat, water, and pressure could 

 be made to reproduce the principal phenomena of metamorphism. 

 The means to effect this are shown in a series of illustrations, the 



