508 HISTORY OF GEOLOGY AND PALAEONTOLOGY. 



precision and lucidity of statement, which opened their con- 

 tents to geologists of all nationalities, and enabled them to 

 exert a great influence upon literature. His Paleontologie 

 Frangaise is a work of the first rank, and after D'Orbigny's 

 death the French Geological Society resolved to continue it. 

 Cotteau, Deslongchamps, Piette, De Loriol, and Fromentel 

 added special portions, but finally the scheme had to be given 

 up for lack both of the means and of scientific workers. 



D'Archiac, who succeeded D'Orbigny as Professor of Palae- 

 ontology in Paris, was thoroughly versed in the geology of the 

 French Jurassic deposits, and in the sixth and seventh volumes 

 of his history of the progress of geology he gave an exhaustive 

 criticism of all the publications on these deposits which had 

 appeared before the year 1856. D'Archiac takes the English 

 development of Jurassic rocks as the basis of comparison, and 

 tries to bring the observations in all other parts of the world 

 into harmony with the main sub-divisions established in the 

 English series. At the same time, he agrees with Dufrenoy, 

 Elie de Beaumont, and D'Orbigny in assuming it to be quite 

 impracticable to carry out any comparison of detailed zonal 

 sequences in distant localities. 



As Quenstedt had not attempted to compare the Swabian 

 development of Jurassic rocks with the succession in other 

 countries, some of his students made a special study of the 

 comparative stratigraphy and palaeontology. O. Fraas travelled 

 through France and England, and afterwards contributed a 

 memoir to the Neues Jahrbuch in 1850. He established the 

 parallelism of many of the zones by means of fossil identifica- 

 tions, and at the same time gave a careful account of the 

 differences of the local facies, and supported Gressly and 

 Quenstedt in their view that the local English names should 

 not be applied to other areas. While Fraas succeeded in 

 demonstrating that the Lias and "brown Jura" of Wiirtemberg 

 were represented by synchronous formations in France, 

 England, and Switzerland, he experienced great difficulty in 

 finding an exact equivalent for the " white Jura " of Wiirtem- 

 berg. 



What Fraas had only indicated in broad features, Albert 

 Oppel, 1 another student of Quenstedt's, worked out in detail. 



1 Albert Oppel, born 1831 at Hohenheim, studied at the Polytechnic 

 School in Stuttgart and under Quenstedt in Tubingen; in 1854 and 1855 

 travelled through France, England, Switzerland, and Germany, in order to 



