106 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



Le Mans, Aurillac, and Limagne. Brard covered a wider field 

 of research, and added still further to the investigation of the 

 fresh-water deposits and their fossils (Annales du Museum, 

 1809, 1810). 



The zoologist, De Ferussac, made a special research of the 

 molluscan species in the fresh-water limestone near Mainz, in 

 Quercy, and in Spain. His publications in the Memoirs of 

 the Institute (1812 and 1813) proved that of about eighty-five 

 species nearly all had become extinct; a few, however, could 

 be identified with species still living in distant neighbourhoods 

 or indigenous to Central Europe. Ferussac confirmed Brong- 

 niart in his opinion that the molluscan species could be used 

 to determine the age of fresh-water deposits. 



So much interest had been aroused in these Oligocene 

 deposits that Omalius d'Halloy, 1 the Belgian geologist, made 

 an examination of the series in Auvergne, Velay, and in parts 

 of Italy and Germany, and in all cases proved conclusively 

 that the fossil remains had been imbedded in the deposits of 

 fresh-water marshes, and were not remains which had been 

 accidentally swept into marine deposits. 



The Belgian geologist supplemented the observations of 

 Cuvier and Brongniart with great success. With unceasing 

 diligence, he conducted geological tours on foot during ten 

 years, and as a result he was enabled to produce a geological 

 map of France and the adjoining territories of Belgium, 

 Germany, and Switzerland. The map gave a faithful represen- 

 tation of the distribution of the leading geological formations. 

 It was first published in 1822, on the scale of i 14,000,000, 

 and was in later years improved and incorporated in D'Halloy's 

 Text-book of Geology. 



Early in his career, D'Halloy had regarded the position of 

 the strata, their horizontal, slightly or highly inclined, or 

 vertical position, of great importance in determining the age 

 of the strata. He thought the horizontal strata corresponded 

 to Werner's " Flotz formations," and all inclined strata to 



* Jean Baptiste Julien d'Omalius d'Halloy, born 1783 in Liege, the only 

 son of a rich aristocratic family, came under the influence of Brongniart, 

 Cuvier, Faujas, and Lamarck in Paris; he devoted himself from 180410 

 1814 wholly to the pursuit of geological researches in France, Belgium, 

 and the neighbouring districts; in 1815 was appointed Governor of the 

 Province of Namur; afterwards a Member of the Belgian Senate, and 

 President of the Academy of Sciences in Brussels; died 1875. 



