274 
ANALYSES OF SOILS. 
therefore clo not exist originally in the organic matter, but are a result brought about by 
the processes to which they have been subjected. 
The rocks under consideration are usually concealed by a great amount of their own 
debris. It is therefore impossible to determine their thickness or their extent; they are, 
however, between one hundred and fifty and two hundred feet thick. 
We have already stated that the shales contain beds of gypsum. The lowest beds are 
merely thin inconsiderable masses, unfit or unprofitable for working ; yet the amount of 
plaster is considerable. The rock itself, with its plaster, would form a very valuable 
manure in many parts of the State. The decomposing shales, when plaster is wanting, 
may be regarded as valuable as gypsum, and perhaps more so ; they have not, however, 
been employed, and hence have not received the sanction of experiment or trial. 
In addition to the plaster beds, the shales embrace a singular deposit, which was called 
by Mr. Eaton vermicular limerock. This deposit, however, is not entitled to a distinct 
name, inasmuch as it is subordinate to the shales, and forms but an inconsiderable mass 
in the group. The vermicular rock is an impure limestone, and is composed of the fol¬ 
lowing elements : 
Water_...______ 0-23 
Organic matter___„_.___ 2*54 
Silex. 3-30 
Carbonic acid_ 20-62 
Alumina_ 5-33 
Magnesia_____ 4-26 
Carbonate of lime _ 13-76 
Protoxide of iron______a trace. 
50-04 in 50 parts. 
The main deposit of plaster is above those porous strata, the composition of which 
has been furnished in the preceding pages. 
The soft green shales pass into thin-bedded limestones, quite compact and hard, and 
which, on being struck, emit a sharp ringing sound similar to clinkstone. These thin beds 
contain the hydraulic limestones, which have been described. 
These parts of the series differ considerably in composition from those below. According 
to Dr. Beck, their composition (the water-limes) is as follows : 
Carbonic acid_ 39-80 
Lime.. 25-24 
Magnesia............ 18-80 
Silica and alumina... 13-50 
Peroxide of iron_ 1-25 
Moisture and loss._....___ 1-41 
100-00 
