OP STRATA. 



45 



Localities, The marine sand occupies a broad strip on the 

 west side of Hudson river, from near Lake Champlain to 

 Greene county ; a distance of one hundred miles— also the 

 north part of New-Jersey, most of the eastern part of the 

 Southern States, the valley of the Mississippi, &c. According 

 to Dr. E. James, the marine sand and crag extend over about 

 four hundred thousand square miles of the great desert be- 

 tween the Mississippi and the Rocky Mountains. 



23 Shell-marl, is in insulated or continued layers, fields, 5- Calca- 



riou3 fonna- 



or patches, in almost every part of the earth. It generally re-tion. 

 poses on marine sand or crag in all bottom grounds ; particu- 

 larly in graywacke districts, as in every part of the Catskill 

 and Allegany range. It is still more abundant in the western 

 valleys of New-York, Mississippi, &c. It may be seen in 

 depressions on primitive rocks, as in Pittsfield, Mass. &c. 

 It consists chiefly of broken, pulverized, and entire shells, of Content«< ot 

 the genus helix (genera helix, planorbis, and lymnaea of La- ^^^^^^ 

 marck.) Calcarious tufa is often in beds in the shell-marl ; 

 which proves it cotemporaneous with it. Consequently the 

 embraced plants of this tufa are antidiluvial. But tufa is now 

 forming in many localities. 



ANOMALOUS DEPOSITES. 



I. Volcanic. Subdivisions. Basalt, which is either, 

 Amygdaloid, when amorphous, of a compact texture, but con- 

 taining cellules, empty or filled. Greenstone trap^ when of a 

 columnar structure, or in angular blocks, often coarse-grained. 

 Variety. Toadstone, when the amygdaloid has a warty ap- 

 pearance, and resembles slag. Volcanic proper, as Lava, ^ava and 

 when dark coloured and nearly homogeneous. Breccia, ce- trachyte, 

 mented grains. Trachyte^ white or grey lava, consisting chief- 

 ly of melted felspar, as pumice, &c. 



Localities. Of the basalt every variety, and every imbedded 

 and every disseminated mineral, may be seen at Deerfield and 

 at Mount Holyoke in Massachusetts ; at New-Haven in Con- 



