184 
THE BOOK OV LIME. 
" Thus marl beds of fi-esh water origin 
may be produced by mechanical deposition 
caused by the gradual evaporation of water 
containing lime, — by chemical deposition 
when the carbonic acid by which it is held in 
solution is given off into the air, or decom- 
posed by the sunshine — by the accumulation 
of the dried shells of visible animals which 
have lived in the water, — and by the depo- 
sition of the minute shields and shells of 
invisible creatures which float in countless 
numbers in every stagnant pool. Of these 
causes the last is probably the most extensively 
l>revalent, and that by which the largest depo- 
sits of marl have been produced." 
A very interesting chapter forms an answer 
to the question which precedes it — " Is lime 
indispensable to the fertility of the soil V A 
question which there is no difficulty in answer- 
ing in the affirmative ; but to answer it so as to 
carry conviction to the mind of the inquirer 
is rendering a double service. As the author 
says, truly enough, "the ])ractical farmer in 
nearly all countries has been accustomed to 
add lime to the soil, but can lime not be 
dispensed with ? Is there no improved mode 
of culture by which the Uhe of lime may be 
superseded ? There are several considerations 
from which an answer may be drawn to this 
question," and we will take the authoi-'s words 
as the best : — 
" P. Extensive and prolonged experience 
has shown that the fertility of many soils is 
increased by the regular addition of lime — 
and that if it be for a series of years withheld, 
such soils become incapable of producing 
luxuriant crops. 
" 2°. All naturally fertile soils are found 
upon analysis to contain a notable proportion 
of lime ; while in many of those yv^hich are 
naturally unproductive, the proportion of lime 
is comparatively small. 
" 3". A naturally productive soil, even 
though regularly manured, is often found, 
after long cropjiing, to become incapable of 
growing particular crops in an abundant or 
healthy manner. On analysis, these soils are 
not unfrequently found to contain only a very 
small proportion of lime; After an addition 
of lime to such soils, it is often observed that 
the diseased or failing crops grow again 
healthily and in abundance. 
" 4°. Lime is often added to one part of a 
farm without producing any visible effect, 
while upon another it greatly increases the 
produce. In such cases, a chemical analysis 
not unfrequently shows that those soils or 
fields on which it produces no effec't already 
contain a sufficient supply of lime. 
" Thus barren sandy soils often admit of 
profit-able cultivation after lime has been added 
— clay Svjils in which no lime can be detected 
are often entirely changed by the addition of 
lime. So, also, it may be laid with profit 
upon soils formed from decaying granite, 
while it is frequently thrown away when 
applied to soils of decayed trap. This is 
chiefly because the gi'anite contains little lime 
naturally, while the trap rocks abound in it. 
" These practical considerations all lead to 
the conclusion th-At lime is really indispensable 
to the fertility of the soil." — Pp. 54, 55. 
The author next discusses the subject of 
how much and how little may or ought to be 
present in the soil, and this is perhaps the 
most interesting part of the work, for doubt- 
less there has been enormous labour lost in 
the profitless application of lime where it was 
not wanting. Upon this subject the author 
says — 
" It is an exceedingly difficult point to 
determine the limits within which the pro- 
portion of lime in a soil ought to be kept in 
order to maintain the highest degree of fer- 
tility. So much depends upon the propor- 
tions of the other ingredients of the soil — 
upon the quantity of sand, of clay, or of 
vegetable matter it contains — that the pecu- 
liar nature of almost every soil would i"equii-e 
to be studied in order to know how much 
lime it ought to contain, or how much may 
be safely added to it with the hope of a pro- 
fitable return. Sandy and peaty soils, when 
dry, require less than such as are naturally 
heavy or undrained. 
" "We know that the limits are really very 
wide within which the proportion of lime in 
the land may be kept without preventing it 
from growing good crops. But there are 
three questions in regard to these limits, to 
which the practical man is interested in ob- 
taining satisfactory answers. How rnucli may 
be present in the soil,' or how little, without 
rendering it unproductive, and what propor- 
tion ought to be present, in order to make it 
fertile in the highest degree. 
" 1°. How MUCH viay be joreseiit? — I have 
already alluded to the practice of deep plough- 
ing in the chalk soils of Surrey and tlie 
neighbouring counties. When five to seven 
inches of pure chalk are brought up and 
mixed with an upper soil only six inches 
deep, it is obvious that the quantity of car- 
bonate of lime in the mixed soil must be very 
great. And if these soils so deepened become, 
under skilful management, more productive 
than before, it is obvious that the presence of 
a very large proportion of carbonate of lime 
will not prevent a soil from yielding good 
crops. 
" Through the kindness of Mr. Davis, in 
sending me a portion of the surface soil of 
such an improved chalk field, near Croydon, 
I have been enabled to analyze it, aud have 
