The Soil, in this our Case, cannot be supplied in Substance, but from the Atmosphere. The Earth which the Rain brings can do it alone, if it fall in great Quantity; for by Water, ’tis plain, the Earth which nourished Helmont’s Tree was supplied; for the Tin-cover of the Box wherein it stood, prevented the Dews from entering.
Dews must add very much to the Land, thus continually tilled and hoed; for they are more heavily charged with terrestrial Matter than Rain is, which appears from their forcing a Descent through the Air, when ’tis strong enough to buoy up the Clouds from falling into Rain: And Dew, when kept in a Vessel long enough to putrefy, leaves a greater Quantity of black Matter at the Bottom of the Vessel, than Rain-water does in a Vessel of the same Bigness, filled with it till putrefied.
Dews at Land, I suppose, are first exhaled from Rivers, and moist Lands, and from the Expirations of Vegetables; most of the Dew which falls on it is exhaled from untilled Land; but most of that which falls on well tilled or well hoed Land, remains therein unexhaled; so that the untilled Ground helps, by that means, to enrich and augment the tilled: For if an Acre be tilled for Two Years together without sowing, it will become richer by that Tillage, than by lying unplowed Four Years, which may be easily proved by Experience[142].
[142]Non igitur Fatigatione, quemadmodum plurimi crediderunt, nec Senio, sed nostra scilicet Inertia, minus benigne nobis Arva respondent. Colum. lib. xi. cap. 1.
But then, as to Rain, the Sea being larger than all the Land (and its Waters, by their Motion, becoming replete with terrestrial Matter), ’tis not unlikely, that more Vapour is raised from One Acre of Sea, than from One hundred Acres of Land.
Some have been so curious as to compute the Quantity of Rain, that falls yearly in some Places in England, by a Contrivance of a Vessel to receive it; and ’tis found, in one of the driest Places, far from the Sea, to be Fourteen Inches deep, in the Compass of a Year; in some Places much more; viz. at Paris, Nineteen Inches; in Lancashire, Mr. Townley found, by a long-continued Series of Observations, that there falls above Forty Inches of Water in a Year’s time.
Could we as easily compute the true Quantity of Earth in Rain-water, as the Quantity of Water is computed, we might perhaps find it to answer the Quantity of Earth taken off from our hoed Soil annually by the Wheat.
But if Land sown with Wheat be not hoed, its Surface is soon incrustate; and then much of this Water, with its Contents, runs off, and returns to the Sea, without entering the Ground; and in Summer a great deal of what remains is exhaled by the Sun, and raised by the Wind, both in Summer and Winter.
Some there are who think it a fatal Objection, that the more an Interval is hoed, the more Weeds will grow in it; and that the Hoe can produce, or (as they say) breed in it as many Weeds in one Summer, as would have come thereon in Ten Years by the old Husbandry. But by this Objection they only maintain, that the Hoe can destroy as many Weeds in One Summer, as the old Husbandry can in Ten Years.
And they might add, that since all Weeds that grow where the Hoe comes, are killed before they seed, and that few of those Which grow in the old Husbandry, are killed[143] before their Seed be ripe and shed; these Objectors will be forced to allow, that our Husbandry will lessen a Stock of Weeds more in one Summer, than theirs can do to the World’s End; unless they believe the equivocal Generation of Weeds, than which Opinion nothing can be more absurd.