INTRODUCTION. 123 



lavas and trap-porphyry (trachyte) in detail; while Hauy 

 introduced the names of pegmatite, diorite, trachyte, aphanite* 

 euphotide, leptinite. 



Brongniart attempted a complete classification of rocks in 

 1813, and introduced the terms diabase, melaphyre, psammite, 

 etc. Fleurien de Bellevue and Cordier made use of the micro- 

 scope for the identification of the components in powdered 

 specimens, but with little success. 



The advances made in these early decades practically repre- 

 sented the progress that could be attained by the use of 

 Werner's method. A new era began for this branch of geology 

 when, in later years, the microscope was applied to the examina- 

 tion of thin rock-sections by transmitted light. 



Very great interest centred round the origin of the massive 

 crystalline and schistose rocks, and widely divergent opinions 

 were held. The Neptunists thought that all' rocks, with 

 the exception of products from active volcanoes, were of 

 aqueous origin. At first the Neptunists and Volcanists dis-< 

 puted only the origin of basalt, which Tobern Bergman, and 

 afterwards Werner and his school, regarded as a sedimentary 

 rock. Almost all French geologists had studied basalt in 

 Auvergne, Velay, Vivarais, or in Ireland, and adopted the 

 view of Desmarest and Faujas de Saint-Fond, that basalt was 

 a volcanic product. 



In Germany, Werner's personal influence kept alive Nep- 

 tunian doctrines even against sharp attacks like those of Voigt 

 (p.- 83). Not a few of the German geologists began to assume 

 an intermediate position. Beroldingen tried to unite the 

 opposite gpinions by suggesting that basalt owed its origin 

 to volcanism, but its form to water. The basaltic magma had 

 solidified on the bed of the ocean, and its pillared, sheet-like, 

 spheroidal, or crystalline form had been developed under the 

 influence of water and hot vapours. In favour of this view, 

 Beroldingen cited the local occurrence of Ammonites, Gryph- 

 ites, and Belemnites in basalt. This observation was, however, 

 afterwards found to have been erroneous. Yet in the course 

 of his discussion, Beroldingen gave expression to many valu- 

 able remarks about volcanic ejecta and the disintegrating 

 changes undergone by volcanic rocks. C. W. Nose, an 

 observer who greatly advanced the geology of the Lower 

 Rhine provinces of Prussia, was of the opinion that basalt 

 and porphyry originated as sedimentary deposits, but were 



