= 
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 
meoceen which is derived from Mr. Maclure. 
erable deposits of bog iron ore occupy the lower 
sauations 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 
brightyyellow to dark brown, are found in abundance i in this 
runes in flat horizontal beds. 
2. Plastic Clay and Sand Formation. 
consists of an indefinite number of beds of sand, clay, 
= and lignite, which appear to alternate without any 
ry exact order. The following is a description of it as it 
occurs in Englan 
ANDS 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 
‘ata. 
CLAYS in beds of various ‘thickness, aad at 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, yellow, 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 elay 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 ‘marle seeieinicr peculiar fossils. 
GRAVEL or small, rounded pebbles form whole 
strata in this ereaiien and exhibit as strongly as the largest 
bowlders, the great attrition which spa must have under- 
gone, to reduce them to their present siz 
LIGNITE, or Wood Coal, always = bessmecane the 
Plastic Clay and sand, and is generally stratified, although 
it sometimes occurs in solitary masses. It usually contains 
amber, and sulphuret of iron. 
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, 
