CHAP. III. Of Pasture of Plants.

Cattle feed on Vegetables that grow upon the Earth’s external Surface; but Vegetables themselves first receive, from within the Earth, the Nourishment they give to Animals.

The Pasture of Cattle has been known and understood in all Ages of the World, it being liable to Inspection; but the Pasture of Plants, being out of the Observation of the Senses, is only to be known by Disquisitions of Reason; and has (for ought I can find) pass’d undiscover’d by the Writers of Husbandry[8].

The Ignorance of this seems to be one principal Cause, that Agriculture, the most necessary of all Arts, has been treated of by Authors more superficially than any other Art whatever. The Food or Pabulum of Plants being prov’d to be Earth, where and whence[9] they take that, may properly be called their Pasture.

This Pasture I shall endeavour to describe.

’Tis the inner or (internal) Superficies[10] of the Earth; or which is the same thing, ’tis the Superficies of the Pores, Cavities, or Interstices of the divided Parts of the Earth, which are of two Sorts, viz. Natural and Artificial.

By Nature, the whole Earth (or Soil) is composed of Parts; and, if these had been in every Place absolutely joined, it would have been without Interstices or Pores, and would have had no internal Superficies, or Pasture for Plants: but since it is not so strictly dense[11], there must be Interstices at all those Places where the Parts remain separate and divided.

These Interstices, by their Number and Largeness, determine the specific Gravity (or true Quantity) of every Soil: The larger they are, the lighter is the Soil; and the inner Superficies is commonly the less.

The Mouths, or Lacteals, being situate, and opening, in the convex Superficies of Roots, they take their Pabulum, being fine Particles of Earth, from the Superficies of the Pores, or Cavities, wherein the Roots are included.

And ’tis certain, that the Earth is not divested or robb’d of this Pabulum, by any other Means, than by actual Fire, or the Roots of Plants.

For, when no Vegetables are suffer’d to grow in a Soil, it will always grow richer. Plow it, harrow it, as often as you please, expose it to the Sun in Horse-Paths all the Summer, and to the Frost of the Winter; let it be cover’d by Water at the Bottom of Ponds, or Ditches; or if you grind dry Earth to Powder, the longer ’tis kept exposed, or treated by these or any other Method possible (except actual Burning by Fire); instead of losing, it will gain the more Fertility.

These Particles, which are the Pabulum of Plants, are so very minute[12] and light, as not to be singly attracted to the Earth, if separated from those Parts to which they adhere[13], or with which they are in Contact (like Dust to a Looking-Glass, turn it upwards, or downwards, it will remain affixt to it), as these Particles do to those Parts, until from thence remov’d by some Agent.

A Plant cannot separate these Particles from the Parts to which they adhere, without the Assistance of Water, which helps to loosen them.

And ’tis also probable, that the Nitre of the Air may be necessary to relax this Superficies, to render the prolific Particles capable of being thence disjoin’d; and this Action of the Nitre seems to be what is call’d, Impregnating the Earth.

Since the grosser Vegetable Particles, when they have pass’d thro’ a Plant, together with their moist Vehicle, do fly up into the Air invisibly; ’tis not likely they should, in the Earth, fall off from the Superficies of the Pores, by their own Gravity: And if they did fall off, they might fly away as easily before they enter’d Plants, as they do after they have pass’d thro’ them; and then a Soil might become the poorer[14] for all the Culture and Stirring we bestow upon it; tho’ no Plants were in it; contrary to Experience.

It must be own’d, that Water does ever carry, in its Interstices, Particles of Earth fine enough to enter Roots; because I have seen, that a great Quantity of Earth (in my Experiments) will pass out of Roots set in Rain-water; and tis found that Water can never be, by any Art, wholly freed from its earthy Charge; therefore it must have carry’d in some Particles of Earth along with it: But yet I cannot hence conclude, that the Water did first take these fine Particles from the aforesaid Superficies: I rather think, that they are exhal’d, together with very small Pieces to which they adhere, and in the Vapour divided by the Aereal Nitre; and, when the Vapour is condens’d, they descend with it to replenish the Pasture of Plants; and that these do not enter intire into Roots, neither does any other of the earthy Charge that any Water contains; except such fine Particles which have already pass’d thro’ the Vegetable Vessels, and been thence exhal’d.

This Conjecture is the more probable, for that Rain-Water is as nourishing to Plants set therein as Spring-Water, tho’ the latter have more Earth in it; and tho’ Spring-water have some Particles in it that will enter intire into Roots, yet we must consider, that even that Water may have been many times exhal’d into the Air, and may have still retain’d a great Quantity of Vegetable Particles, which it received from Vegetable Exhalations in the Atmosphere; tho’ not so great a Quantity as Rain-water, that comes immediately thence.

These, I have to do with, are the Particles which Plants have from the Earth, or Soil; but they have also fine Particles of Earth from Water, which may impart some of its finest Charge to the Superficies of Roots, as well as to the Superficies of the Parts of the Earth[15] which makes the Pasture of Plants.

Yet it seems, that much of the Earth, contain’d in the clearest Water, is there in too large Parts to enter a Root; since we see, that in a short time the Root’s Superficies will, in the purest Water, be cover’d with Earth, which is then form’d into a terrene Pasture, which may nourish Roots; but very few Plants will live long in so thin a Pasture, as any Water affords them. I cannot find one as yet that has liv’d a Year, without some Earth have been added to it.

And all Aquatics, that I know, have their Roots in the Earth, tho’ cover’d with Water.

The Pores, Cavities, or Interstices of the Earth, being of two Sorts, viz. Natural and Artificial; the one affords the Natural, the other the Artificial Pasture of Plants.

The natural Pasture alone will suffice, to furnish a Country with Vegetables, for the Maintenance of a few Inhabitants; but if Agriculture were taken out of the World, ’tis much to be fear’d, that those of all populous Countries, especially towards the Confines of the frigid Zones (for there the Trees often fail of producing Fruit), would be oblig’d to turn Anthropophagi, as in many uncultivated Regions they do, very probably for that Reason.

The artificial Pasture of Plants is that inner Superficies which is made from dividing the Soil by Art.

This does, on all Parts of the Globe, where used, maintain many more People than the natural Pasture[16]; and in the colder Climates, I believe, it will not be extravagant to say, ten times as many: Or that, in Case Agriculture were a little improved (as I hope to shew is not difficult to be done), it might maintain twice as many more yet, or the same Number, better.

The natural Pasture is not only less than the artificial, in an equal Quantity of Earth; but also, that little consisting in the Superficies of Pores, or Cavities, not having a free Communication[17] with one another, being less pervious to the Roots of all Vegetables, and requiring a greater Force to break thro’ their Partitions; by that Means, Roots, especially of weak Plants, are excluded from many of those Cavities, and so lose the Benefit of them.

But the artificial Pasture consists in Superficies of Cavities, that are pervious to all Manner of Roots, and that afford them free Passage and Entertainment in and thro’ all their Recesses. Roots may here extend to the utmost, without meeting with any Barricadoes in their Way.

The internal Superficies, which is the natural Pasture of Plants, is like the external Superficies or Surface of the Earth, whereon is the Pasture of Cattle; in that it cannot be inlarg’d without Addition of more Surface taken from Land adjoining to it, by inlarging its Bounds or Limits.

But the artificial Pasture of Plants may be inlarg’d, without any Addition of more Land, or inlarging of Bounds, and this by Division only of the same Earth.

And this artificial Pasture may be increas’d in proportion to the Division of the Parts of Earth, whereof it is the Superficies, which Division may be mathematically infinite; for an Atom is nothing; neither is there a more plain Impossibility in Nature, than to reduce Matter to nothing, by Division or Separation of its Parts.

A Cube of Earth of One Foot has but Six Feet of Superficies. Divide this Cube into Cubical Inches, and then its Superficies will be increas’d Twelve times, viz. to Seventy-two Superficial Feet. Divide these again in like Manner and Proportion; that is, Divide them into Parts that bear the same Proportion to the Inches, as the Inches do to the Feet, and then the same Earth, which had at first no more than Six Superficial Feet, will have Eight hundred Sixty-four Superficial Feet of artificial Pasture; and so is the Soil divisible, and this Pasture increasable ad Infinitum.

The common Methods of dividing the Soil are these; viz. by Dung, by Tillage, or by both[18].