MARYLAND GEOLOGICAL SURVEY 39 



which, greensand was found with the Lower Chalk of Europe. In 

 1838, Ducatel published a short paper dealing with the geology of 

 Cecil county. This contribution was devoted largely to pointing out 

 localities of various minerals and rocks, and as the subject was ap- 

 proached from an economic side little, if anything, was added to the 

 geological knowledge of the region. In 1841, Booth wrote a memoir 

 on the geology of Delaware, in which he subdivided the formations 

 of that state into Primary, Upper Secondary, Tertiary and Recent. 

 As many of the formations in Cecil county run directly over into 

 Delaware, Booth's classification would apply in great measure to 

 Cecil county as well. The Primary formation included the Crystal- 

 line rocks; the Upper Secondary, Tertiary and Recent formations 

 were confined to the Coastal plain. In 1853, Marcou brought out his 

 monograph on the " Geology of North America," In this volume 

 he published two maps, one of which represented the Piedmont of 

 Cecil county as composed of Secondary, Transition and Primitive 

 rocks ; and the Coastal Plain was represented as built up of Alluvian. 

 In the other map, he showed the Piedmont region as composed of 

 Eruptive and Metamorphic rocks, and the Coastal Plain of Creta- 

 ceous. It will thus be seen that at the middle of the last century such 

 little progress had been made in the stratigraphy of Cecil county 

 that when Marcou came to sum up the results, he found the problem 

 in about the same condition as when Maclure left it, almost fifty 

 years before. 



In order to bring out with more clearness the progress which has 

 been made in differentiating the various formations within Cecil 

 county, they will be taken up in turn from this point, beginning 

 with the oldest. 



The Crystalline Bocks of the Piedmont Plateau. 

 The first report of Philip T. Tyson as State Agricultural Chemist 

 of Maryland appeared in January, 1860. In this paper he published 

 an able summary of the geology of Maryland, and indicated the 

 position and extent of the various formations on a geological map. 

 The crystalline rocks of Cecil county are represented on this map 



