Marsh — Jurassic formation on the Atlantic Coast. 443 



similar exhibition is to be seen, as represented in the second 

 drawing. This is repeated on a much larger scale further 

 south, near Canon City, Colorado, as likewise shown in still 

 another sketch, but none of these colored drawings does justice 

 to the natural scenery. 



On the Atlantic coast, the same combination of colors, 

 although less brilliant, may be seen in the Potomac outcrops 

 in Maryland, now proved by vertebrate fossils to be likewise 

 Jurassic. Further north, the reds predominate in this horizon 

 across Delaware and Pennsylvania, but in the plastic clays of 

 New Jersey, the strong distinct colors, usually in horizontal 

 bands, are dominant. On Staten Island and at various out- 

 <jrops along the, northern shore of Long Island, as vvell as on 

 Block Island, the same horizon is distinctly marked by varie- 

 gated patches, while still further east, at Gay Head, on Martha's 

 Vineyard, the most startling color display of the whole Atlantic 

 coast forms a flaming beacon that mariners and geologists alike 

 liave for a century held in high esteem. I know of no other 

 horizon of 'equal extent so readily distinguished from all others 

 by its physical features. 



Early Investigations. 



In the early days of American geology, the pioneers here, 

 as in other branches of science, attempted to refer everything 

 to European standards. In this way, strata of various ages, as 

 we now know, were called by European names, and were sup- 

 posed to represent equivalents. In this general way, the terms 

 Lias, Oolite, etc., were applied to strata on the Atlantic coast. 

 It was soon found, however, by the actual workers in the field, 

 that our geological sequence had only a general correspondence 

 with that of Europe or of other parts of the world, yet some 

 geologists still endeavor to harmonize the time tables, but with 

 only moderate success. It is, however, now becoming known, 

 that this continent had its own law of development, and that 

 its fauna and flora must be studied by themselves to disclose 

 their full significance. The time ratios of America certainly 

 do not coincide with those of Europe. The long periods of 

 Mesozoic time represented in Europe by great deposition of 

 many series of strata were marked here by other means as 

 well. The rich fauna and flora- that then lived here do not 

 have their exact counterparts elsewhere. 



The apparent absence on the Atlantic coast of the Jurassic 

 as known in Europe naturally led the early geologists to seek 

 its equivalent strata. The first supposed identification seems 

 to have been recorded by W. B. Pogers, who called the eastern 

 Virginia coal beds Oolitic."*^ These beds are now regarded as 

 Triassic. 

 * Transactions Association American Geologists and Naturalists, yol. i, p. 300, 1843. 



