186 BULLETIN OF THE BUSSEY INSTITUTION. 
much or more of these supplementary fertilizing constituents. Prac- 
tically, shell-lime, where it is to be had at all, usually costs less than 
the other forms of lime; and it is probable that it is actually a little 
better for agricultural purposes than stone-lime, such as is obtainable 
hereabouts, because of the small quantities of fertilizing matters, other 
than lime, that are contained in it. 
The advantage to be derived from using sea-shells in a finely 
powdered condition, rather than in their natural form, has often been 
noticed. But it is to be observed, in this regard, that the smallness of 
the proportion of nitrogen in sea-shells teaches very emphatically that 
there is nothing to be gained by pulverizing the shells with mechanical 
appliances, instead of by means of fire; or, rather, that no useful con- 
stituent will be lost by resorting to the cheaper device of burning the 
shells to quick-lime, as a means of reducing them to powder. When 
the quick-lime is slaked with a small quantity of water, it falls, of 
course, to a fine dust ; and the process of burning has the further merit 
of reducing the weight of the shells, and the cost of transporting the 
lime in them, nearly one-half. 
It is to be observed, furthermore, that the organic matter in unburnt 
oyster-shell may do actual harm in that it commonly tends to protect the 
calcareous matter from the solvent action of water, carbonic-acid water, 
and the other chemical agents that exist in the soil. Thus, Bischof * 
found not only that the membranes between which the carbonate of lime 
in oyster-shells is enclosed protect the lime-salt in a high degree against 
the action of dilute muriatic acid, but that fragments of oyster-shell are 
much less easily soluble than chalk or limestone in carbonic-acid water ; 
and that the interior pearly part of the shell is less soluble than the outer 
portion. 
On exposing fresh oyster-shell to. the action of carbonic acid in water 
for twenty-four hours, it was found that 1,000 parts of water saturated 
with carbonic acid had dissolved of 
Lamina from the interior of the shells . . . . . 0.028 
The same, powdered . ..... « « « » | = nn 
Chips from the exterior . . . . 5 ... «nn 
According to Bischof, the lamin from the interior of the shells require 
for solution thirty-six times as much carbonic acid water as chalk, and 
one hundred times as much as precipitated carbonate of lime; the chips 
from the exterior fourteen times as much as chalk, and forty times as much 
as the artificial carbonate. ‘That the crystalline condition of carbonate of 
* In his “ Elements of Chemical and Physical Geology.” London: 1854, 1. 
pp. 181, 182. . 
