422 Reviews — A. Daubree' s Experimental Geology. 



of water under pressure in the formation of dolomite, whilst the 

 numerous minerals accumulated in metalliferous lodes, which ob- 

 servation had shown could not have been conveyed either in a state 

 of volatilization or of fusion, attracted attention with a view to their 

 reproduction in the wet way — no easy task, when it was seen that 

 silica itself in separating from water assumes the condition of opal 

 rather than of quartz. This void in synthetic mineralogy Senarrnont 

 filled by the employment of appropriate substances, such as are 

 most widely distributed in existing thermal springs, operating at 

 temperatures above 100° C, and under pressure. In this way he 

 succeeded in the formation of quartz crystals, small, it is true, but 

 possessed of the physical and optical as well as the chemical pro- 

 perties of natural quartz. Since then another triumph of synthesis 

 has been scored by Hautefeuille in the artificial production of orthose 

 and albite. 



Such is a brief outline of the very useful historical sketch which 

 Mons. Daubree gives as a prelude to the results of his own researches, 

 which, after being continued for 40 years, and scattered through 

 many publications, are now comprised in one volume. This will 

 enable the reader more fully to estimate the value of his labours, 

 and at the same time will materially assist the geologist who has 

 not cai-ried on similar work. The bearings of experimental geology 

 may assist in explaining many of the chemical, physical, and mechan- 

 ical phenomena which he meets with in the field, and the causes of 

 which are difficult to understand, considering the complex subsequent 

 modifications which have too frequently masked their primal origin. 



The first section of the volume deals with chemical and physical 

 phenomena in three chapters ; wherein the author shows the applica- 

 tion of the experimental method, 1st, to the history of metalliferous 

 deposits, 2nd, to the study of metamorphic and eruptive rocks, 3rd, 

 to the history of volcanic phenomena. A portion of the second 

 section, where the author describes the chemical decomposition of 

 silicates, such as felspar, by mechanical causes, in part belongs to 

 the subjects discussed in the first section. 



The historij of metalliferous deposits is divided into (1) stanni- 

 ferous masses, (2) '-'gites sulfures," commonly called plumbiferous, 

 (3) " gites de platine." 



In dealing with the Stanniferous group M. Daubree can point out 

 how accurately he described in the " Annales des Mines," nearly 

 forty years ago, the origin and constitution of tin deposits. The 

 peculiarities of this group — so different from the other, in which 

 the electro negative is mainly sulphur — are noted; the minernl 

 occurs as an oxide, and the gangues are not the same. The metalli- 

 ferous fissures, too, are not like ordinary lodes in the proper sense of 

 the term, but seem to be more like a number of small shrinkage 

 cracks, and the neighbouring rock is charged for some distance with 

 the mineral (cassiterite). This network of small veins contains an 

 enormous proportion of quartz, and the oxide of tin is further 

 escorted by certain minerals unusual in ordinary lodes. — such as 

 topaz, pycnite, tourmaline (schorl), axinite, and also apatite, — so 



