Reviews — A. Daubree's Experimental Geology. 421 



IE& IE ~V I IE W S. 



I. — Etudes Synthetiques de Geologie experimental^. Premiere 

 partie. Application de la methode experimental a l'etude de 

 divers phenoruenes geologiques. Par A. Daubree. 8vo. (Paris, 

 1879.) 



T has been objected to geology as a science that its conclusions 

 were frequently based upon insufficient premises, and that it was 

 lacking in actual demonstration. Indeed a writer of eminence once 

 described geologists as a set of persons who amused themselves by 

 constructing worlds and then pulling them to pieces again ; and it 

 must be confessed that the reckless guesses of an imagination not 

 always scientific, which have at times obtained a temporary notoriety, 

 did in some cases justify the charge. Still it should be remembered, 

 as Mons. Daubree points out, that the study of the Earth, after having 

 been for a long time hypothetical, did really, towards the end of the 

 last century, enter " une voie positive," where it has taken for its 

 guide the observation of facts. 



Exactly a century has elapsed since the first appearance of de 

 Saussure's works on the Alps. Werner and Hutton followed 

 shortly, and the endless dissertations of their respective disciples 

 may perhaps have had something to do with the strictures pre- 

 viously mentioned, especially as they took root in those soils where 

 discussion on subjects more or less transcendental seems to be an 

 indigenous plant. Yet, even in the earliest years of the present 

 century, the importance to the geologist of the synthesis of minerals 

 was recognized, although it was at one time considered that the 

 divergence between certain minerals and the most analogous com- 

 pounds which the laboratory could furnish was such as to render 

 their actual reproduction impossible. The difference between crys- 

 talline quartz and the amorphous silica of the chemist was almost 

 as great as that between the diamond and the soot of our chimneys. 

 To effect such marvels, lapse of time and certain occult actions were 

 deemed necessary, or, as Leibnitz put it in the Protogcea, "il faut du 

 temps, du repos, et de l'espace." 



In 1805 Hall experimented with a view to control some of 

 Hutton's views, and succeeded in making chalk semi-crystalline 

 under the influence of heat and pressure, whilst Haussmann, a few 

 years after, turned to account in the interpretation of geological 

 phenomena the .examination of the silicates of the metallurgical 

 furnaces. 



The year 1823 marks a discovery of the utmost importance. Mit- 

 scherlich recognized that peridot, pyroxene, and other mineral species 

 crystallized in slags, and Berthier, by melting silica with different 

 bases in definite proportions, actually obtained crystalline combina- 

 tions identical with those of Nature, especially pyroxene. It was the 

 first step made in the direct synthesis of minerals. 



The next step was to overcome the difficulty presented by in- 

 soluble combinations in the wet way, and Haidinger, being desirous 

 of controlling Von Buch's hypothesis, inaugurated the employment 



