TERTIARY FORMATION. 267 
This deposite contains hydrate of iron, and but few 
organic remains. 
The second division embraces the plastic clay. 
This is well exhibited at Gay's Head (Martha's 
Vineyard), and consists, in general, of interstratified 
inclined layers of gravel, conglomerates, sands, 
variegated clays, iron ore, and lignite. These clays 
and sands are of different colours and texture, and 
contain shark's teeth, crocodile bones, and other 
organic remains. 
Some of the remains of a shark were discovered 
at Gay's Head, which Professor Hitchcock esti- 
mates to have been from thirty to fifty feet long. 
This result corresponds with the conclusions of 
European geologists, that the extinct animals were 
much larger than those now existing, and that all 
<)limates were of a tropical character. The lignite 
(coal) which occurs in it forms beds sometimes 
several feet thick, or is mingled with the clay in 
comminuted dark masses, resembling peat, through 
which logs are interspersed. Sometimes the woody 
fibre is very distinct. 
The plastic clay formation, distinguished by inter- 
stratified lignites with amber, and the relics of ma- 
rine animals and terrestrial vegetation, lies imme- 
diately above the green sand formation, which is 
the equivalent of the chalk of Europe, though want- 
ing in this country, and extends from Cape God to 
the borders of the Gulf of Mexico. 
In the State of New- York the tertiary formation 
forms a deposite from the head of Lake Champlain 
to its outlet, extending about four miles from the 
lake on the west side, and from six to twelve miles 
on the east, interrupted, however, occasionally by 
primary rocks, which jut up against the lake shore. 
It forms a bed averaging twenty-five feet thick, 
composed of clays and sands, and embracing ma- 
rine shells or relics of a very recent date. The 
tertiary extends above the level of the lake about 
200 feet. 
