Mr. _Bradley_, and all Authors, I think, are of Opinion, that Plants of different Natures are fed by a different Sort of Nourishment; from whence they aver, that a Crop of Wheat takes up all that is peculiar to that Grain; then a Crop of Barley all that is proper to it; next a Crop of Pease, and so on, ’till each has drawn off all those Particles which are proper to it; and then no more of these Grains will grow in that Land, till by Fallow, Dung, and Influences of the Heavens, the Earth will be again replenish’d with new Nourishment, to supply the same Sorts of Corn over again. This, if true (as they all affirm it to be), would prove, that the Air is not the Food of Vegetables. For the Air being in itself so homogeneous as it is, could never afford such different Matter as they imagine; neither is it probable, that the Air should afford the Wheat Nourishment more one Year, than the ensuing Year; or that the same Year it should nourish Barley in one Field, Wheat in another, Pease in a Third; but that if Barley were sown in the Third, Wheat in the First, Pease in the Second, all would fail: Therefore this Hypothesis of Air for Food interferes with, and contradicts this Doctrine of Necessity of changing Sorts. I suppose, by Air, they do not mean dry Particles of Earth, and the Effluvia which float in the Air: The Quantity of these is too small to augment Vegetables to that Bulk they arrive at. By that way of speaking they might more truly affirm this of Water, because it must be like to carry a greater Quantity of Earth than Air doth, in proportion to the Difference of their different specific Weight; Water, being about 800 times heavier than Air, is likely to have 800 times more of that terrestrial Matter in it; and we see this is sufficient to maintain some Sort of Vegetables, as Aquatics; but the Air, by its Charge of Effluvia, _&c._ is never able to maintain or nourish any Plant; for as to the Sedums, Aloes, and all others, that are supposed to grow suspended in the Air, ’tis a mere Fallacy; they seem to grow, but do not; since they constantly grow lighter; and tho’ their Vessels may be somewhat distended by the Ferment of their own Juices which they received in the Earth, yet suspended in Air, they continually diminish in Weight (which is the true Argument of a Plant) until they grow to nothing. So that this Instance of Sedums, _&c._ which they pretend to bring for Proof of this their Hypothesis, is alone a full Confutation of it. Yet if granted, that Air could nourish some Vegetables by the earthy Effluvia, _&c._ which it carry’d with it [6]; even that would be against them, not for them.