On the Phosphoric Strata of the Chalk Formation. 59 
will probtahly be retained. The coprolites exist in some parts 
of SuOolk and Essex in very large quantities ; but as it is not the 
intention of this paper to enter upon a description of the crajr 
coprolites, which it is to be hoped Professor Henslow may himself 
at some future time lay before the agricultural public, it is 
sufficient to state that the coprolites can be obtained in almost 
unlimited quantity, and that the beds can be easily and econo- 
mically worked. 
The proportion of phosphate of lime in these coprolites is 
from 50 to 60 per cent.* So far, therefore, we have in England 
an abundant source of phosphate of lime. It is, however, to be 
observed, that the coprolites are intensely hard, that very power- 
ful machinery is required to grind them, and that, even when in 
powder, the phosphate of lime is not of itself sufficiently soluble 
for direct application to the soil. Tlie coprolites are readily 
dissolved by sulphuric acid, and then afford a most valuable 
manure, of which many hundreds of tons have already been 
manufactured and used. 
It may naturally occur to some person to ask. To what pur- 
pose — if there already exists an abundant and cheap supply of 
phosphate of lime in the coprolites of the crag — to what purpose 
should the agriculturist be troubled with looking for another ? 
or in what respect are the beds of the chalk formation about to 
be described of interest in a practical point of view? The answer 
to these questions may be readily given — the mechanical and 
chemical processes necessary to prepare the Suffolk coprolites 
for agricultural use must doubtless, to a certain extent, prevent 
their being brought into the market at so low a price as they 
might be, were such preparation unnecessary. 
On the other hand, there is reason to believe that the phos- 
phoric substances of the upper and lower green-sand may, 
without chemical preparation of any kind, be applied to the 
turnip and other crops with great benefit, and (as will be shown 
in this paper) that they may be reduced to the requisite degree of 
fineness by simple and inexpensive machinery. 
Again, it is confidently believed, that by proper investigation, 
founded upon the details here brought forward, every occupier 
of land lying on given zones of the chalk formation may find, 
either in phosphoric fossils or phosphoric marls, the means of 
very materially increasing the productiveness not only of his own 
* Note by Mr. Way. — Two analyses of the coprolites made in my 
laboratory gave phosphoric acid equal to 52 and 54 per cent, of bone-earth 
phosphate. Dr. Gilbert informs me that in several analyses which he has 
made of samples taken from many tons of the ground coprolites, lie has 
found the percentage of bone-earth phosphate to be very uniformly 
between 55 and 57 per cent. 
