ECONOMICAL GEOLOGY. 
1ST 
much from this circumstance, that is from the mechanical state of the 
substances present, as from any deficiency of them ; and this difficulty, as 
well as the other, in part, would be much alleviated by the use of quick- 
lime and ashes. There is a great deal of land of the above description 
among the foot hills and low spurs of the mountains : while the higher 
ranges have generally a productive soil and are covered with luxuriant 
forests; the former being composed of argillaceous and micaceous slates 
and schists, while the latter are more frequently made up of syenytesand 
hornblende gneisses and slates. 
This completes the list of soils, as far as analyzed : but it is only a be- 
ginning of the work which ought to be accomplished in this direction, 
and which would be, if the survey were in a condition to employ a 
chemist constantly. 
SECTION IE FERTILIZERS. 
MARLS. 
Marl is very abundant in North Carolina and very widely distributed, 
and of several kinds, the principal of which are four, viz : Green-sand, 
Eocene, Miocene and Triassic. The former has generally but a small per- 
centage of carbonate of lime, 5 to 30 ; the second, usually d0 to 95 ; the 
third, 20 to 60; and the fourth, generally less than 50. The last is of 
little consequence as a fertilizer, because of the very limited extent of its 
outcrops, and it is scarcely used where abundant. It will be remembered 
as a frequently recurring term in the Egypt coal section, described in the 
previous chapter. These marls are more extensively exposed than else- 
where in the northwestern part of Wake county and in the edge of 
Orange, between Morrisville and Durham. There are frequent outcrops 
of a bed of marl and impure limestone, 2 to d feet thick, over a territory 
of 15 or 20 square miles, the nearly horizontal strata coming to the sur- 
face in ravines and gullies, and exposed in ditches, wells, &c. Near Brass- 
field turnout, on Mr W. Rochell’s place, is an exposure of nearly d feet 
of alternate thin beds of a compact, light gray and red arenaceous lime- 
stone, with strata of uncompacted brick red, marly clay between. This 
middle portion has the following composition : 
Carbonate of Lime, 2d.07 
“ Magnesia, 7.52 
Silica, d7.20 
Alumina,. 15. 8d 
Oxide of Iron, d.76 
