In Page 13. he concludes thus: ‘That Hills, in their Measure, contain only as much profitable Land as the Plain or Plat of Ground they stand upon; and as a Proof of that, all Vegetables or Plants have an erect Method of Growth.’
This Proof of Mr. Bradley’s is founded upon an Argument which has no Consequence, unless it were first proved, that the Surface of Earth could produce and maintain as many Vegetables or Plants as could stand thereon in an erect Posture; which Supposition is as impossible, as that half an Acre should produce and maintain an Hecatomb, without Mr. Bradley’s teaching Oxen to live upon Air for their Food, as he thinks Van Helmont’s Tree did.
All expert Husbandmen must needs be convinced, that the greatest Crop of Vegetables that ever grew, might stand in an erect Posture, upon a twentieth (and I may say the Hundredth) Part of the Surface that produced it; therefore there must be Nineteen Parts for the Roots to spread, unoccupied by the Trunks, Stems, or Stalks.
And tho’ it be true, that an Hill will support no more of these, than its Base, when placed in an erect Posture, close together, as in a Sheaf; yet this close Position is only proper for them when they are dead, and require no more Nourishment than Houses and Pales do; and consequently require no Room but to stand on. Therefore this Argument of Mr. Bradley’s must not be admitted in vegetative Growth, where there is always required Nineteen times more Room in the Surface, for the Use of the Roots, than what the Stems, Trunks, or Stalks, do possess upon it: And the more Room there is for the Roots, the greater Number of Plants may be produced.
Neither can I admit, that all Vegetables or Plants have an erect Method of Growth; because the contrary is seen in Chamomile, and divers other Vegetables, which have an horizontal Method of Growth.
But what is more material to this Purpose, to be observed, is, that all Vegetables have horizontal Roots, and Roots parallel to the Earth’s Surface or Superficies; and unless those Roots have a sufficient Superficies of Earth to range in, for Nourishment of a Plant, the Stem and Branches cannot prosper, whatever be their Method of Growth above the Earth; and if there be not a due Quantity of Food for the Roots within the Earth, a very little Space may contain the external Parts of Vegetables upon it.
From what has been said, I think we may conclude, that Mr. Bradley’s Hill may produce more Vegetables than the Base whereon it stands; and therefore it is of more Value than half its superficial Measure; i. e. Two Acres on the Hill are worth more than one Acre on the Plain, the Soil being equally rich, as he allows it to be, in his Case.
Now, indeed, whether Mr. Bradley might not possibly be deceived in his Opinion of the equal Richness of his Hill, and his Plain, I will not dispute: I will only say this, that ’tis generally otherwise. But where a Plain is plow’d up into moderate Ridges, their Height being in proportion to the Depth of the Staple, below which the Plough must take nothing into the Ridges, the Soil is equally rich, whether it be plowed plain, or ridged up. And as the Surface is in the Ridges increased, there is nothing in all Mr. Bradley’s Arguments, that shews, why that increased Surface should not produce more Vegetables than the same Earth could do whilst it was level.
There are other Reasons why it should produce more when ridged[223], besides the Increase of Surface; as,
I. ’Tis then more free from the Injuries of too much Water.