2io The Founders of Geology LECT. 



marls, lie traced what he believed to be the limits of 

 the sheets of freshwater in which they were successively 

 deposited. Still more precise was the grouping adopted 

 by Lavoisier. This great man, who, if he had not given 

 himself up to chemistry, might have become one of the 

 most illustrious among the founders of geology, was, as 

 you will remember, associated early in life with Guettard 

 in the construction of mineralogical maps of France. As 

 far back as the year 1*789, he distinguished between what 

 he called littoral banks and pelagic banks, which were 

 formed at different distances from the land, and were 

 marked by distinct kinds of sediment and peculiar organ- 

 isms. He thought that the different strata, in such a 

 basin as that of the Seine, pointed to very slow oscilla- 

 tions of the level of the sea, and he believed that a section 

 of all the stratified deposits between the coasts and the 

 mountains would furnish an alternation of littoral and 

 pelagic banks, and would reveal by the number of strata 

 the number of excursions made by the waters of the 

 ocean. Lavoisier accompanied his essay with sections 

 which gave the first outline of a correct classification of 

 the Tertiary deposits of the Paris region. His sketch was 

 imperfect, but it represented in their true sequence the 

 white Chalk supporting the Plastic Clay, lower sands, 

 Calcaire Grossier, upper sands and upper lacustrine lime- 

 stone. 1 



A few years later, a still more perfect classification of 

 the Tertiary deposits around Paris was published by 



1 M6m. Acad. Roy. Sciences (1789), p. 350, pi. 7. This memoir of 

 Lavoisier on modern horizontal strata and their disposition is fully 

 noticed by Desmarest in the first volume of his Geographic Physique, 

 p. 783. 



