58 
REVIEW ©E LIEBJS. 
these effects, which take place gradually and | 
slowly, are principally occasioned by the presence 
of sulphuretted hydrogen and its compounds, more 
particularly the hydrosulphuret of ammonia, in 
the air. Lastly, if the vegetable kingdom is the 
great means of purifying the air, and retaining it 
in a fit state for the respiration of men and an¬ 
imals, the absorption and decomposition of sul¬ 
phuretted hydrogen by plants must constitute not 
the least important of their functions.” 
We believe, too, but can not lay our hands upon 
the passage, that Dr. Lankester had previously 
brought forward some evidence to show that sul¬ 
phuretted hydrogen is not injurious to vegetation. 
The source from which sulphur is obtained by 
plants is not the atmosphere, according to Dr. 
Liebig, but the soil, whence it is furnished by the 
decomposition of sulphates. “ The air,” he says, 
(p. 63,) “ can not contain any substances in which 
sulphur is present, unless, indeed, we except mi¬ 
nute and scarcely appreciable traces of sulphuret¬ 
ted hydrogen.” We confess our inability to un¬ 
derstand this. That ammonia is obtained from 
the air was one of the author’s triumphant proofs, 
and yet it exists there in as minute and inappre¬ 
ciable a quantity as sulphuretted hydrogen; and 
we can not comprehend why the latter should not 
be thus supplied as well as the former. If not, 
what, let us ask, becomes of the volumes of this 
gas continually escaping from the surface of the 
soil ? Are we to suppose that it is all consumed 
in forming sulphurets ? Surely not. 
Next to sulphur stand phosphates in their im¬ 
portance to vegetation. This, indeed is not a new 
doctrine; on the contrary, their value was pointed 
out in the former editions; not, however, we 
think, so strongly as now. We are rejoiced to 
find Prof. Liebig ranged on this side of the ques¬ 
tion, for it seems to us that if practical agriculture 
points out one thing more strongly than another, 
it is the great importance of phosphates. Nothing 
is more remarkable than the action of the super¬ 
phosphate oflime on plants in gardens; no single 
agent that we have yet seen employed can be 
compared to it. This probably arises from garden- 
soil being rich in all other substances except phos¬ 
phoric acid, which is always largely carried off, 
and but sparingly returned in the processes of gar¬ 
den-culture. The remarks of Prof. Liebig on this 
subject are too striking to be omitted:— 
“ In a former letter I showed you how great a 
waste of phosphates is unavoidable in England, 
and referred to the well-known fact that the im¬ 
portation of bones restored in a most admirable 
manner the fertility of the fields exhausted from 
this cause. In the year 1827 the importation of 
bones for manure amounted to 40,000 tons, and 
Huskisson estimated their value to be from 
100,000/. to 200,000/. sterling. The importation 
is still greater at present, but it is far from being 
sufficient to supply the waste. 
“ Another proof of the efficacy of the phosphates 
in restoring fertility to exhausted land is afforded 
by the use of the guano—a manure which, although 
of recent introduction into England, has found 
such general and extensive application. 
“We believe that the importation of one hun¬ 
dred-weight of guano, is equivalent to the impor* 
tation of eight hundred-weight of wheat—the 
hundred-weight of guano assumes in a time which 
can be accurately estimated the form of a quantity 
of food corresponding to eight hundred-weight of 
wheat. The same estimate is applicable in the 
valuation of bones. 
“ If it were possible to restore to the soil of 
England and Scotland the phosphates which dur¬ 
ing the last fifty years have been carried to the 
sea by the Thames and the Clyde, it would be equiv¬ 
alent to manuring with millions of hundred-weights 
of bones, and the produce of the land would in¬ 
crease one third, or perhaps double itself in five or 
ten years. 
“ We can not doubt that the same result would 
follow if the price of the guano admitted the ap¬ 
plication of a quantity to the surface of the fields, 
containing as much of the phosphates as have been 
withdrawn from them in the same period. 
“ If a rich and cheap source of phosphate of 
lime and the alkaline phosphates were open to 
England, there can be no question that the impor¬ 
tation of foreign grain might be altogether dis¬ 
pensed with after a short time. For these ma¬ 
terials England is at present dependant upon for¬ 
eign countries, and the high price of guano and of 
bones prevents their general application, and in 
sufficient quantity. Every year the trade in these 
substances must decrease, or their price will rise 
as the demand for them increases. 
“ According to these premises, it can not be dis¬ 
puted, that the annual expense of Great Britain 
for the importation of bones and guano is equiv¬ 
alent to a duty on grain : with this difference only, 
that the amount is paid to foreigners in money. 
“ To restore the disturbed equilibrium of consti¬ 
tution of the soil,—to fertilize her fields,—England 
requires an enormous supply of animal excrements, 
and it must therefore excite considerable interest 
to learn that she possesses beneath her soil beds 
of fossil guano , strata of animal excrements, in a 
state which will probably allow of their being em¬ 
ployed as a manure at a very small expense. The 
coprolithes discovered by Dr. Buckland, (a discov¬ 
ery of the highest interest to Geology,) are these 
excrements; and it seems extremely probable that 
in these strata England possesses the means of 
supplying the place of recent bones, and therefore 
the principal conditions of improving agriculture— 
of restoring and exalting the fertility of her fields. 
“ In the autumn of 1842, Dr. Buckland pointed 
out to me a bed of coprolithes in the neighborhood 
of Clifton, from half to one foot thick, enclosed in 
a limestone formation, extending as a brown stripe 
in the rocks, for miles along the banks of the Sev¬ 
ern. The limestone marl of Lyme Regis con¬ 
sists, for the most part, of one fourth part of fossil 
excrements and bones. The same are abundant 
in the lias of Bath, Eastern and Broadway Hill, 
near Eversham. Dr. Buckland mentions beds, sev¬ 
eral miles in extent, the substance of which consists 
in many places, of a fourth part of coprolithes. 
“ Pieces of the limestone-rock of Clifton, near 
Bristol, which is rich in coprolithes and organic re¬ 
mains, fragments of bones, teeth, &e., were sub¬ 
jected to analysis, and were found to contain above 
