INTRODUCTION. 57 



Werner knew the best of the new work that was being done 

 elsewhere. From all parts of Europe students came, and, 

 when they returned to their own countries, they spread the 

 teaching of geognosy and mineralogy as Werner had taught it 

 to them. It was the spoken word of Werner that carried. Of 

 written words no man of genius could have been more chary. 

 His dislike of writing increased as he grew older, till he 

 could scarcely bring himself to reply to the most important 

 letters. Cuvier relates that the letter which announced to 

 Werner that he had been elected a Foreign Member of the 

 French Academy was left unopened by the Professor and was 

 never answered. 



With the exception of a number of mineralogical papers, and 

 a short classification and description of the different rock- 

 formations, Werner published only a single work on the origin 

 of dykes, and a series of very short articles on basalt, trap- 

 rock, and the origin of volcanoes. He never published his 

 academical courses of lectures ; for an account of these we 

 have to turn to notes published by his students, sometimes in 

 abridged and sometimes in extended form. Werner had, how- 

 ever, more than once to disown these published notes, as they 

 failed to represent the true sense of his lectures. 



The most trustworthy reports of Werner's " geognosy " are 

 probably those written by Franz Ambros Reuss in the third 

 part of his text-book (Leipzig, 1801-3); by D'Aubisson de 

 Voisins in his Traite de Geognosie (Strasburg and Paris, 1819); 

 and by Jameson in the Elements of Geognosy (Edinburgh, 1808). 

 Werner himself published only one lecture "Introductory to 

 Geognosy " delivered at Dresden. 



Werner denned "Geognosy" as the "Science which inquires 

 into the constitution of the terrestrial body, the disposition of 

 fossils (i.e. minerals, cf. p. 15) in the different rock layers, and 

 the correlation of the minerals one to another." In his 

 lectures, he began with a short epitome of mathematical and 

 physical geography, and with a discussion of the natural 

 agencies which alter the conformation of the globe. 



Proceeding to the consideration of the earth's crust, Werner 

 described all the varieties of rock and entered in detail into 

 their structure, their position, their chronological succession, 

 and their technical value as rich or poor metalliferous layers. 

 Certain varieties of rock (shale, limestone, trap-rock, porphyry, 

 coal, talc, and gypsum) were thought by Werner to have been 



