788 
THE TROPICAL 
AGRICULTURIST. [March j, 1882. 
vat, and these are sprinkled with well-washed animal 
charcoal, in rather coarse grains ; in this case the char- 
coal deprives the oil during the passage of a certain 
amount of impurity, while the renewed clean cotton in 
the funnels does its work so well, that the oil reassurnes 
its wonted clearness. It is then put up in kegs and 
barrels, and is ready for home consumption or export- 
ation. 
EFFECT OF MANURES ON CROPS. 
(Field, 3rd December 1881.) 
In a former article (The Field, 19th November,) hav- 
ing stated that the effect of manures on crops in various 
localities was not always the same, as the conditions 
were certain to be different, we then merely alluded to 
those conditions, but now propose to call attention to 
some of them at least. 
It is true that but little is as yet known concerning 
the full effect which they are likely to exert, and we 
do not propose to enter fully into all details as far as 
they are known, for that would be impossible in the 
space at our disposal; but our intention is rather to 
point out the principal influences at work, so that those 
who take an interest in the subject of experimental 
manuring may be the better enabled to draw conclusions 
from such results as they may obtain practically, after 
allowance has been made for the effect of the locality. 
The extent to which allowances should be made is at 
present unknown ; and it will only be by repeated trials 
that the necessary corrections will be discovered. First, 
all the constituents for plant life must be present in the 
soil. This we may consider as an axiom concerning 
which there can be no dispute ; but more than this is 
requisite, the plant food must be in such a condition 
that it can be with ease absorbed or assimilated. This 
1 1 iter condition does not always obtain ; it is quite poss- 
i ,Ie for two soils to be almost identical in chemical 
composition, in so far that each constituent is present 
iii the two soils in the same quantity ; but still one of 
the soils may be fertile, the other not so. This differ- 
ence is due to a want of similarity in the arrangement 
of the constituent parts. In one case they are combined, 
so as to be readily dissolved by water, and thus rendered 
accessible to the plant, whereas in the other the arrange- 
ment is otherwise. 
A fertile soil will not require manuring to any great 
extent, and it is doubtful whether the addition of much 
manure would be productive of any corresponding gain. 
The time when a great gain by manuring occurs is, as 
is well known, after the soil has been exhausted by a 
former crop, when certain of its constituents which were 
soluble have been remove], and then either a fresh 
pwi 'iou must be rendered soluble, or manures must be 
added. In the latter case the same end is attained, 
and in a shorter time. The improvement of the soil is 
therefore due to cultivation and manuring; but the ex- 
tent to which this occurs is largely dependent upon 
properties inherent in the soil, and also upon external 
influences. Granted that the soil of the locality is norm- 
al in composition, whether it be a clay or a sandy 
loam, that it is not absolutely deficient in any one con- 
stituent, there are then three distinct physical properties 
of the soil which most probably have a definite though 
indirect influence on. the action of manures, and these 
properties are — porosity, colour, and character of the 
surface. We have said "indirect influence" as being 
in opposition to the direct influence of the constituents 
of the soil upon the manures. The time which elapses 
after the land lias been thoroughly wetted before it be- 
comes fit for irorkinj ., i Largelj dependent upon porosity, 
which, so long as it is not possessed in too high a 
degree, is of great value. A soil which is too porous 
is said in common parlance to be "hungry;" then the 
manure, instead of being retained, is readily washed 
down and out of the reach of the plant ; on tie other 
hand, want of porosity causes a soil to be wet, and 
then aeration cannot take place, the very substances 
which compose the soil do not become altered and ren- 
dered soluble, and the excess of vegetable matter is not 
decomposed. However, a wet soil has one redeeming 
feature — when once waim, it retains its heat much 
longer than if it were dry. 
The colour and character of the surface are, as a rule, 
of great efieet, dark coloured soils being warmed by the 
heat of the sun quicker than those lighter coloured, and 
the presence of vegetable matter, which produces the 
dark tint, appears to retard the cooling ; hence the changes 
in the composition of the soil, which require a moder- 
ate temnerature, -will proceed more rapidly in a dark 
soil, and the presence of small stones on the surface is 
likewise useful, as it prevents the soil below from coot 
ing too" rapidly at night. 
From what we have just said, it is evident that the 
lay of a field is of great importance, as the amount of 
heat received from the sun on a southern slope is not 
only greater than that received by the same area on the 
level, but the above physical conditions to which we have 
cursorily referred, make themselves felt, which v. oul 1 not 
be the case were the field on a northern slope. 
We must not omit the influence exerted by the shelter 
of trees, whether for good or evil. In many parts of 
England, more especially in the north, trees and hedge- 
rows have been reduced to a minimum, under the sup- 
position that the land in the neighbourhood will become 
drier. Such a supposition is no doubt true, as under 
the lea of large hedges the land has not much opport- 
unity of getting rid of superfluous moisture, and the 
precipitation of the rain by trees, if a fact, is reduced in 
quantity. But, on the other hand, trees and hedges 
contribute a considerable amount of shelter from the 
wind, reducing the evaporation of water from the surface, 
and consequently the temperature of the earth. How- 
ever, it becomes a question to be decided by experience, 
whether dryness probably accompanied by a lower temp- 
erature of the soil is or is not preferable to a moister 
condition, but with less movement of the air, accom- 
panied by a slightly higher temperature. This last state 
of affairs has been tried for some time, and it remains 
but to hear the opinions of those who are working under 
the new system ; for our own part, we are inclined to 
think that the old method, with better drainage, would 
be preferable. 
Such, then, are some of the various physical con- 
ditions of a soil which can be judged of by the eye, and 
which will tend to produce a variation in the results 
obtained by manuring different soils with the same 
quantities of manure. 
We can hardly conclude this article without mention- 
ing one or two chemical conditions which are only in- 
dicated by analysed of the soil. Superphosphate added 
to a soil deficient in lime is but of small value, as, in- 
stead of being fixed by the lime which ought to be 
there, and retained for the plant's use, it passes away 
too readily in the drainage. A highly ferruginous soil 
is likewise unsuited for the application of a superphos- 
phate, becase the iron present fixes the superphosphate 
in such a form that it becomes of no use to the plant. 
It is almost needless to state that the proportions of 
those manures which are already well represented in 
the soil might be reduced, were our knowledge in a 
more advanced state. At prese nt we are only in pos- 
session of a fe»v facts, which tend to show that the ad- 
dition of manure to soil already well supplied is unaccom- 
panied by a corresponding increase in the yield. 
GINSENG ROOT, AND ITS DIGGERS. 
BY GUT LA TOURETTE. 
(Oil and Drug Neios.) 
The Amorican ginseng (Aralia quinquefolia) is one of 
the most graceful and beautiful plants that adorn the 
