Sand Formation of the United States. ^9S 



qu'ils sont perces de troiis de Tarets, (Teredo) qui ont remplis pos- 

 terieurement par de la pyrite." The last two circumstances are 

 common to our own lignites. 



Humboldt, in his Tableau des Formations Geologiques, gives as a 

 synonym of the ferruginous sand series, Gres secondaire a Lignites, 

 in contradistinction to his Gres tertiaire a Lignites^ or Plastic Clay 

 formation. 



. Cuvier* describes the green sands of France as containing both 

 lignite and amber : the former is abundant in the green sand between 

 Dives and Fecamp. The iron sand of England, say Phillips and 

 Conybeare,f contains a considerable quantity of fossil wood ; while 

 in the neighborhood of Folkstone and Cambridge, the lignite even 

 retains the woody fibre. 



I will adduce but one other instance — that of the lignite beds in 

 the green sand in the Isle d'Aix, near La Rochelle. At this place 

 is a submarine forest of dicotyledonous trees, sometimes bituminous 

 and brittle, and again having the texture of jet. These lignites are 

 perforated by the Teredo, and accompanied by amber. J 



I have detailed these facts to shew (what some have doubted) that 

 the vast deposits of lignite with amber, lately exposed in the Dela- 

 ware and Chesapeake canal, do not offer insurmountable objections 

 to the position I have taken — that the beds in which those substances 

 occur are secondary. 



I am aware, however, that some European geologists, relying more 

 on the superposition of strata than on their organic products, have re- 

 ferred all those formations I have just quoted, to the tertiary class, 

 including therein the whole chalk formation. But I am disposed in 

 this case to adopt the opinion of Humboldt, who is known to con- 

 sider fossil remains merely as collateral aids in deciding the relative 

 position of strata. " Malgre les analogies que presentent les gres a 

 lignites (sables verts et argiles plastiques) au-dessous et au-dessus 

 de la Craie, cette formation pourtant appartient plutot au terrain se- 

 condaire qu'au terrain tertiaire, auquel plusieurs geognostes celebres 

 le rapportent."|| 



It is almost certain, however, that the real plastic clay formation 

 does occupy a considerable tract in New Jersey, Maryland, &;c. In 

 a letter recently addressed to me by Prof. Eaton, is the following 



* Disc, sur les Revolutions, p. 294. t Geol. p. 137. 



t Humboldt's Gissement dcs Roches, p. 294. 



II Gissement dps Roches, p. 278. 



