REPORT ON THK GEOI.OGY OF NORTH AMERICA. 55 



either mere casts, or almost entirely obliterating them. In its 

 descent it is seen to become charged with ferruginous matter, 

 staining the fossils near the upper surface of the marl of a deep 

 brown colour, and coating whatever it overflows with a ferrugi- 

 nous incrustation. 



I have nowhere seen a better example of the changes which 

 the infiltration of water can effect upon strata than may be wit- 

 nessed in these marl deposits of New Jersey, where every variety 

 of dissolving and cementing agency is in hourly operation upon 

 a large scale. 



The mineral contents of these secondary strata of New Jersey 

 are, iron pyrites in profusion, lenzinite, peculiar spheroidal 

 masses of a dark green colour, carbonate and phosphate of lime 

 occasionally replacing the fossils in the form of casts. Lignite 

 is extremely abundant ; it is found in the lower strata of the 

 Chesapeake and Delaware canal, in almost every variety from 

 charred wood to well- characterized jet. 



The following appears to be the most usual order of the above- 

 described cretaceous strata in New Jersey : 



1 . Dark ferruginous sandstone and conglomerate, consisting 

 of limpid quartose sand, cemented by a dark brown ferruginous 

 paste ; contains also some of the green grains. 



2. Rubbly calcareous stratum. 



3. Arenaceous stratum, being chiefly a yellow sand, mingled 

 with a greater or less share of the green grains, or marl, and a 

 small quantity of clay. Sometimes thirty or forty feet thick. 

 Fossils usually in the state of casts. 



4. Marl. A mass of little else than the chloritic grains, loose 

 and uncemented, 10 or 12 feet thick; full of fossils. 



5. A red ferruginous sandstone, full of the impressions and 

 casts of shells ; — the particles being limpid quartz sand, and 

 some green grains. 



With respect to the basis upon which the greensands of New 

 Jersey rest, nothing is known with certainty. Although a sec- 

 tion was made in cutting the Chesapeake and Delaware canal, 

 of nearly one hundred feet deep, the upper part through the 

 beds of the ancient alluvium, and the lower through those of the 

 cretaceous period, no older formation was reached. There seems 

 good reason to believe, however, from the nonappearance of 

 any formations along the Atlantic plain of an age correspond- 

 ing to the oolite and new red sandstone groups of Europe, that 

 the superior secondary beds repose, wherever they are developed 

 in the States north of Alabama, upon i-ocks of the primary class. 

 In Alabama, on the other hand, where the primary formations 

 do not extend, the probability is, that they rest upon rocks of 



