212 
THE CULTIVATOR. 
agriculture, I will select that which concerns one sub¬ 
ject, viz: the circulation of the sap. We all know that 
plants are nourished by their sap, just as animals are 
by the blood which circulates through their veins. 
If we inquire for the point at which the sap enters a 
plant, we find it to be the root, but not all parts of the 
root alike. There is a peculiar class of organs whose 
office it is to absorb nourishment from the soil; and 
these are situated along the fibres or smaller subdivi¬ 
sions of the root; of course it is at these points and no 
others that the sap enters. Let us see if we can make 
any practical application of this knowledge. If we 
wish by manuring, to assist the growth of a tree, we 
should place the manure at some distance from the point 
at which the trunk enters the ground, so that it may lie 
as nearly as possible over the fibres of the root. If we 
wish to plant a vine so as to twine around a tree and be 
supported by it, we should plant it very near to the point 
at which that tree enters the ground, rather than at the 
distance of several feet from it; because in this way the 
two will interfere least with each other’s growth. If we 
wish to transplant a tree, we should be more careful 
about the extremities, than about the main divisions of 
the root. If the root have several branches, it is better 
to cut off all those branches excepting one, and retain 
that with all its subdivisions perfect, than to cut off the 
ends of all the branches, as is the common practice. 
Again—if we trace the course of the sap during the 
different seasons of the year, we find that in such trees 
as the oak, the hickory and the chestnut, it circulates 
principally in the sapwood during the spring and sum 
mer, but during the autumn and winter it retires to the 
heart-wood, and not to the root, as is generally suppos¬ 
ed. In order to satisfy ourselves of this, nothing more 
is necessary than to take a part of the body of a small 
tree cut in the spring, and of another cut in the winter, 
and lay them on the fire. The sap will be seen to ex¬ 
ude in the first from near the surface; in the second 
from the heart. Let us see if we can make any practi¬ 
cal application of this knowledge. It is generally ac¬ 
knowledged that, that most destructive disease in tim¬ 
ber called the dry-rot arises from the presence of the sap. 
It is generally the heart-wood which we use for timber, 
whilst the sap-wood is considered of little value. If then 
the situation of the sap at different seasons is such as 
I have just mentioned, in order to get our timber free 
from the sap, we should cut it in the summer and 
not in the winter. The course thus indicated is, I 
know, in direct opposition to the common practice 
of men. As this is a matter of some practical im¬ 
portance, permit me to cite one fact in confirmation 
of the rule which I have laid down. The fact is men¬ 
tioned in connexion with many others of a similar cha¬ 
racter, in a communication from a very intelligent ship- 
carpenter to one of our scientific periodicals. “In ac¬ 
cordance with the common practice of ship-carpenters, I 
was in the habit of cutting my timber in the winter.— 
During the summer of 1810, when engaged in framing 
a vesssel, I found I had no piece which was suitable for 
a certain place in the frame. It was necessary that the 
work should go on, and as the only alternative left me, 
I sent immediately to the woods and had a suitable stick 
cut; this I framed in with the others. After several 
years the vessel was sent back to me to be repaired.— 
On examining her side-timbers, I found them all more 
or less affected with the rot, excepting this one, whilst it 
was perfectly sound.” 
Again; if we inquire into the nature of the sap, we 
find that as it enters the vegetable system, it consists 
mainly of water holding carbonic acid gas in solution 
Water has the power of absorbing large quantities of 
certain gases, whenever it is brought in contact with 
them. Strange as it may seem to those who have ne¬ 
ver thought much on the subject, water is porous, and 
absorbs these gases just as a sponge absorbs water.— 
The great object of manuring, in most instances, is to 
supply carbonic acid gas to the growing plant. A 
large portion of this gas is liberated from vegetable 
matter during its decay; and hence the value of such 
matter as manure. The gas furnished by t ie manure, 
must be absorbed by the water, as it sinks down into the 
ground. Of course, the water should meet the manure 
before reaching the roots, and not after it has passed 
beyond them. This would suggest that the manure 
could be placed to the best advantage upon the surface, 
because then the water must pass through it before 
meeting with any of the roots. But, then, there is a 
difficulty arising from another source. The valuable 
material furnished by the manure, is furnished in the 
form of a gas. If the manure is placed upon the sur¬ 
face, it soon dries, and whilst in that state, as the gas 
is liberated, no water being present to absorb it, it is 
soon dissipated in the atmosphere. The two facts ta¬ 
ken in connexion, suggest that the manure should be 
placed as near the surface as is consistent with its be¬ 
ing kept in a moist state, and in every instance, above 
the roots of the plant which it is intended to benefit. 
Where manure is spread upon the ground in the fall 
to benefit a winter crop, it should be placed very near 
to, if not upon the surface; where it is spread in the 
spring or early part of su m mer it should be always 
covered with earth. 
Our knowledge of the nature of sap, enables us to 
explain the manner in which clover improves land.— 
Had we no experience on the subject, it would seem, 
to say the least, improbable that any crop could im¬ 
prove land. We would naturally suppose that plants 
were nourished by the ground itself—that they fed up¬ 
on the soil. If such be the case, when a crop is plough¬ 
ed under and decays, it can give nothing but what it 
has first taken; and how then can it improve land ?— 
Yet we find that growing clover upon land, and then 
ploughing it under and suffering it to. decay, is one of 
the very best methods of improving land. Bearing in 
mind the nature of the food of plants, this admits of a 
simple explanation. We will suppose that clover is 
sown upon a perfectly barren spot. The atmosphere 
which is above this spot, contains a portion of carbo¬ 
nic acid gas, for all atmospheric air contains a greater 
or less portion of it. A rain comes ; as the rain falls, 
it absorbs a portion of this gas, and in this condition 
enters the ground. No sooner does it come in contact, 
with the seed in the first instance and with the root af¬ 
terwards, than it is absorbed and its materials used for 
increasing the size of the vegetable structure. When 
the portion of air above the spot, has in this way been 
exhausted of carbonic acid, a supply is obtained from 
the neighboring portions, in consequence of that strong 
tendency which gases manifest, to intermix and diffuse 
themselves throughout each other. This process is re¬ 
peated again and again, and thus the clover increases 
in size. Perhaps some one may ask, from whence is 
this gas obtained in the first place ? From many sour¬ 
ces, but principally from decaying vegetables, such as 
are found in the woods and along the fence sides. The 
quantity of the several elements which enter into the 
composition of our globe, is fixed; it is impossible for 
man either to increase or diminish this quantity, and it 
is equally impossible for him to convert one of these 
elements into another. All he can do is to make an 
economical use of that which already exists, to gather 
up those portions which subserve no valuable ends, and 
apply them to use. This is what the farmer does in 
sowing his land with clover. He impresses the very 
wind into his service, for every wind that sweeps over 
a field of clover, laden as that wind is with the mate¬ 
rials of vegetable structures, is made to contribute to 
its growth. After a large portion of vegetable matter 
has, in this way, been collected upon the once barren 
spot, it is ploughed under and secured for future use. 
Again; in absorbing nourishment from the earth, the 
roots of a plant do not seem to exercise any choice; 
but drink up every thing, presented to them in a suffi¬ 
ciently fluid state. This we learn from actual experi¬ 
ment. Almost any substance which is soluble in water, 
may be made to enter vegetable systems. After a hete¬ 
rogeneous mass is thus taken up by a plant, such por¬ 
tions as are suited to its nourishment are retained, whilst 
such as are not suited, are returned to the roots, and by 
them again deposited in the soil. From observation, 
we learn that the matter thus rejected, is thrown back 
in such a state as to be not only unsuitable to the nou¬ 
rishment of the plant (rejecting it) but positively dele¬ 
terious. It has also been ascertained, that the substan¬ 
ces rejected by different plants differ from each other; 
and this to such an extent that the matter rejected by 
one plant, is well adapted to the nourishment of ano¬ 
ther. With a knowledge of these facts, we can assign 
the reason, why it is not a good plan to sow the same 
crop upon the same piece of land for several years in 
succession. It will not do to say (as is often done) 
that a second crop of wheat will not grow as well upon 
the same spot, as the first, because that spot has been 
so much exhausted by the first. This is, it is true, one 
reason; but if it be the only reason, or even the prin¬ 
cipal reason, why is it that a crop of corn succeeds so 
well? The failure in the second crop of wheat, arises 
not so much from the exhaustion of the soil, as from 
that soil’s containing a portion of matter positively de¬ 
leterious to the growth of wheat, and which was depo¬ 
sited by the first crop. At the same time this matter is 
not injurious to the growth of corn, and hence the crop 
of corn is almost as good as it would have been, had 
wheat never been sown upon the land. If we could as¬ 
certain the precise character of the matter which is re¬ 
tained, and of that which is rejected, by each of the 
several crops commonly cultivated, it would be an easy 
matter to determine the best order in which crops can 
succeed each other. Perhaps too, if this subject was 
better understood, we should find that the way in which 
some manures benefit crops,is not by supplying nutritious 
matter to them, but by removing this deleterious matter 
from their roots. If this matter possess the character 
of an acid, as it is more than probable it does in some 
cases, lime would act in this way. Being a salefiable 
base, it would unite with the acid and neutralize its pro¬ 
perties. 
I might go on and multiply instances such as these, 
did the occasion call for it: but as my object is, not to 
give a lecture on vegetable physiology; but by illustrat¬ 
ing its application to agriculture, to show its impor¬ 
tance to the farmer, these will suffice. Perhaps some 
one may ask, if scientific principles are nothing more 
than facts, arranged and generalized, why is it, that 
knowledge in this form, is more valuable, than in the 
form of unconnected observations; the form in which 
this knowledge is at first obtained ? 
There are several reasons. Knowledge in the form 
of science is more easily retained, and is more perfect¬ 
ly at the command of the possessor, than it can possi¬ 
bly be, in the form of unconnected observations. I 
doubt not that the experience of every one here will 
confirm the statement, that it is easier to remember fif¬ 
ty effects, when we can trace them to one common 
cause, than it is to remember five, when we can trace 
them to no cause. A knowledge of the cause of any 
number of effects, serves as a band, by which they are 
bound in one common bundle, and thus secured from 
being scattered and lost. It is one of the characteris¬ 
tics of science, that the relation between cause and ef¬ 
fect is distinctly traced out. 
Another reason why it is desirable to have our know¬ 
ledge in the form of science is, that in this form it will 
serve to direct us in our course of experiment and ob¬ 
servation. Such is the constitution of nature, so inti¬ 
mately are the various parts of creation interwoven, 
that a cause generally gives rise to several effects.— 
When we have traced an observed effect back to its cause, 
we can generally infer other effects, which will spring 
from the same cause; and these often of a character 
entirely different from the one first observed. To illus¬ 
trate my meaning by an instance. In attempting to 
sink a pump to an uncommon depth, it was found that 
the water could not be raised by it, to a height greater 
than thirty-two feet. The cause of the rise of the wa¬ 
ter was ascertained to be the weight of the atmos¬ 
phere. The reason why the water would not rise to a 
heighth greater than 32 feet, was that the weight of a 
column of our atmosphere was only equal to that of a 
column of water of the same diameter, and 32 feet high. 
It was at once inferred, that as the weight of the atmo¬ 
sphere was fixed, it must sustain columns of different 
liquids at heights, inversely proportioned to their spe¬ 
cific gravities. And again; that as we rose from the 
level of the sea, leaving as we must, a part of this at¬ 
mosphere behind us, the height at which a column of 
any liquid would be sustained, must diminish in propor¬ 
tion to our rise. Thus by tracing the refusal of a pump 
to act in certain circumstances, to its cause; we ascer- 
tain, in the first place, a method of determining the 
specific gravity of liquids ; and in the second place, a 
method of determining the height of mountains. The 
effects by which we determine these things, spring from 
the same cause as the refusal of a pump to act, and yet 
they are of such a character that we never should have 
dreamed that there was any connexion between them, 
had we not traced them to their common cause; and 
more than this, we should probably have remained long 
in ignorance of the two last mentioned effects, had we 
not traced the first to its cause. Thus it is, that throw¬ 
ing knowledge into the form of science, is like putting 
it out at compound interest. 
Another reason why it is important to have our know¬ 
ledge in the form of science, is that in this form it will 
greatly assist us in observing facts, and collecting in¬ 
formation. When the attention has been directed to 
any particular subject, facts connected with that subject 
are observed and remembered, which, in other circum¬ 
stances, although they might have passed before the 
eye, would have made no impression on the mind.—• 
Let a farmer and an architect travel together, through 
the same country, you will find that although they must 
have seen the same things, yet they have brought home 
with them entirely different kinds of information. The 
farmer can give you an account of the soil, the condi¬ 
tion of the crops, the methods of cultivation, &c. ; 
whilst he can tell you little or nothing of the structure 
of the buildings which he has passed. The architect, 
on the other hand, can give you a minute description 
of every principal building on the way, whilst he can 
tell you little or nothing respecting the crops. The dif¬ 
ference arises entirely from the fact, that these two 
men have had their attention previously directed to dif¬ 
ferent subjects. By throwing our knowledge into the 
form of scientific principles, we get a number of sub¬ 
jects worthy of attention, distinctly out before the mind, 
and each of them will be a nucleus around which know¬ 
ledge will naturally collect. 
Such are some of the arguments, which urge a. study 
of natural science upon the farmer. The want of suc¬ 
cess, which has in many instances attended the efforts 
to apply science to agriculture, may be brought for¬ 
ward as an objection, by some. To such I would an¬ 
swer, this want of success is to be attributed, in part 
to the present imperfection of those sciences which 
most naturally apply to agriculture; and in part also, 
to the visionary character of many of those who have 
hitherto made the attempt. If you will consult the 
history of the application of science to those of the arts 
to which it has been most successfully applied, you will 
find that this has been a misfortune which has happen¬ 
ed to them ail, in their infancy. Visionary men being 
the lightest part of society, seem always to rise to the 
top; and rising science, like the rising sun, is forced 
to shed its first rays upon those barren spots, where it 
is impossible that any thing should grow. Let it rise 
higher, and pour its flood of light upon the rich valleys 
below, and if it cause not these to spring with life and 
verdure, then may you fairly call its claim in question. 
If the attempt has failed hitherto, in consequence of 
having been made by visionary men, the greater is the 
necessity that sober, substantial, practical men should 
now take the matter in hand. 
Much has already been done in Virginia for the ad¬ 
vancement of the interests of agriculture. A geologi¬ 
cal survey of the state is now in progress. An able 
periodical, devoted exclusively to diffusing information 
respecting the best methods of cultivating and improv¬ 
ing land, has been established, and thus far well sus¬ 
tained. And last, though not least, societies such as 
that whose anniversary we to-day celebrate, have been 
established in many parts of the state. Thus far it is 
well. There is yet another, and, as it appears to me, 
an important step to be taken. The nature of that step 
and my reasons for believing it important, I have pre¬ 
sented before you. “I have spoken as unto wise men, 
judge ye what I say.” 
Every inducement is held out to the farmer of the 
valley to improve his land and his system of cultivation. 
