24 The Founders of Geology LECT. 



no sign of any acquaintance with these in his maps or 

 memoir. His work, therefore, excellent as it was for the 

 time, contained little in common with the admirable 

 detailed geological maps of the present day, which not only 

 depict the geographical distribution of the various rocks, 

 but express also their relations to each other in point of 

 structure and relative age, and their connection with the 

 existing topography of the ground. 



In the course of his journeys, Guettard amassed a far 

 larger amount of detailed information than could be put 

 upon his maps. From time to time he embodied it 

 in voluminous essays upon different regions. The longest 

 and most important of these is one in three parts on the 

 mineralogy of the neighbourhood of Paris, in which, 

 besides giving an account of the distribution of the 

 minerals and rocks, he pays special attention to the organic 

 remains of that interesting tract of country, and figures a 

 large number of shells from what are now known as the 

 Secondary and Tertiary formations. 



His natural history predilections led him to take a keen 

 interest in the fossils which he himself collected, or which 

 were sent up to Paris from the country for his examination. 

 He devoted many long and elaborate memoirs to their 

 description, and figured some hundreds of them. I may 

 mention, as of particular interest in palseontological 

 investigation, that Guettard was the first to recognize 

 trilobites in the Silurian slates of Angers. In some 

 specimens which had been sent up to the Academy 

 from the quarries of that district, he observed numerous 

 impressions of organic remains, which he referred to sea- 

 weeds and Crustacea. The latter he sagaciously compared 



