ECONOMICAL GEOLOGY. 189 
Sulphuric Acid, 043 2.10 0.26 0.31 
Water, 9.13 8.26 7.55 11.22 
The most valuable ingredients of these marls are potash and phosphoric 
acid. It was long supposed that their high fertilizing effect was due to 
the potash chiefly, but it has been ascertained that the phosphoric acid is 
the constituent which determines the agricultural value. Number 1 is 
one of the best varieties, containing unusually high percentages of both 
these important elements ; although some pits are richer in one, or the 
other. Number 2 is one of the poorer sorts. These two samples repre- 
sent the famous Squankum beds, some of which are wrought by com- 
panies on a large scale. Number 3 is from the pits of the West Jersey 
Marl Transportation Company, and contains a vory high percentage of 
potash. Number 4 is pronounced “ A marl of the first quality and a fair 
sample of those of the neighborhood.” Number 5 “Is a good sample of 
the blue marl.” And yet neither of them is rich in phosphoric acid or 
lime. 
This greensand is widely distributed over the southeastern half of New 
Jersey. It occurs in horizontal beds of great thickness and various com- 
position. The characteristic compound however is, of course, the green 
sand , which consists of minute rounded grains of a green colored min- 
eral, soft enough to be crushed by the nail, and known in mineralogy as 
glauconite , a hydrated silicate of almnnina and iron, with potash and 
magnesia. The different strata contain different proportions of this min- 
eral mixed with clay, quartz sand, and sometimes a considerable per- 
centage of carbonate of lime. Some of the best layers of marl contain 
90 per cent, and upward of the green sand. An average of some two 
dozen analyses given by Prof. Cook gives 75 per cent., the range being 
from about 30 to 90. In North Carolina the proportion of green sand is 
very small, not often passing from 5 to 10 cent., and only occasionally 
rising to 25 or 30. 
By reference to the map and to the previous chapter, it will be seen 
that this marl owcurs throughout the southeastern region of the State, 
between the Neuse River and the Cape Fear. The following analyses 
will furnish the means of comparing these marls with those of New Jer- 
sey, and also of estimating their agricultural value : 
A 
B 
C 
D 
E 
Silica, Insol., 
93.43 
37.00 
91.00 
79.00 
89.70 
“ Soluble, 
1.46 
0.20 
0.60 
Oxide of Iron and Alum. 
9.00 
640 
4.70 
8.80 
5.00 
26 
