34 Finch on the Tertiary Formations 



1. Ferruginous Sand. 



This formation, which occupies a situation between the 

 oolites and chalk in England, is to be traced in the following 

 description, which is derived from Mr. Machire. 



Considerable deposits of bog iron ore occupy the lower 

 situations in New-Jersey, and many of the more elevated 

 and dividing ridges are crowned with a sandstone, and pud- 

 dingstone. Quantities of ochres, varying in color from 

 Ijright yellow to dark brown, are found in abundance in this 

 stratum, in flat horizontal beds. 



2. Plastic Clay and Sand Formation 

 consists of an indefinite number of beds of sand, clay, 

 gravel and lignite, which appear to alternate without any 

 Very exact order. The following is a description of it as it 

 occurs in England. 



SANDS of various colors, in beds varying from an inch 

 to fifty feet in thickness ; the pure white silicious sands 

 used for making Glass are generally obtained from these 

 strata. 



CLAYS in beds of various thickness, and of the bright- 

 est and most variegated hues, so that they have sometimes 

 been compared to the colors on the leaves of a tulip : white, 

 red, blue, grey, yellovi', black, indeed almost every variety of 

 color may in different situations be traced in these clays. 

 Their utility is great, as in fact they are necessary for the 

 porcelain manufacturer, potter, for bricks, and every pur- 

 pose where a pure clay is required ; some of the varieties 

 stand the heat of the strongest fires, and are used in Glass 

 houses; sometimes it assumes the appearance, or is repla- 

 ced by marie containing peculiar fossils. 



GRAVEL or small, rounded pebbles form whole 

 strata in this formation and exhibit as strongly as the largest 

 bowlders, the great attrition which they must have under- 

 gone, to reduce them to their present size. 



LIGNITE, or Wood Coal, always accompanies the 

 Pla§tic Clay and sand, and is generally stratified, although 

 it sometimes occurs in solitary masses. It usually contains 

 amber, and sulpburet of iron. 



The Plastic clay and sand formation may be readily iden- 

 tified wherever it presents itself, the character of the clays 

 and their bright color, and the alternation of beds of clay, 



