The Experiments they insist upon are chiefly two; the first is, that Mint, and several other Plants prosper and thrive very greatly in Water. The other is this; they take a certain quantity of Earth, and bake it in an Oven; then they weigh it, and put it into an Earthen Pot. Having well water'd this Earth, they make choice of some fit Plant, which, being first carefully weigh'd, they set in it. There they let it grow, continuing to water it for some time, till 'tis much advanced in bigness: Then they take it up; and though the Bulk and Weight of the Plant be much greater than when first set, yet upon baking the Earth, and weighing it, as at first, they find it little or not at all diminished in weight; and therefore conclude, 'tis not the Earth but Water, that nourishes and is turn'd into the Substance of the Plant.
I must confess I cannot see how this Experiment can ever be made with the nicety and justness that is requisite, in order to build upon it so much as these Gentlemen do. 'Tis hard to weigh Earth in that quantity, or Plants of the size of those they mention, with any great exactness; or to bake the Earth with that accuracy, as to reduce it twice to just the same Driness. But I may wave all this; for though the Experiment be never so easily practicable, and all the Accidents of it exactly as they set forth, yet nothing like what they infer can possibly be concluded from it; unless Water, which they so plentifully bestow upon the Plant in this Experiment, be pure, homogeneous, and not charged with any terrestrial Mixture; for if it be, the Plant after all may owe its Growth and Encrease intirely to that.
Some Waters are indeed so very clear and transparent, that one would not easily suspect any terrestrial Matter were latent in them; but they may be highly saturated with such Matter, though the Eye be not presently able to descry or discern it. 'Tis true, Earth is an Opake Body; but it may be so far dissolved, reduced to so extreme small Particles, and these so diffused through the watry Mass, as not sensibly to impede Vision, or render the Water much the less diaphanous. Silver is an Opake, and indeed a very dense Body; and yet, if perfectly dissolved in Spirit of Nitre, or Aqua Fortis, that is rectified and thorowly fine, it does not darken the Menstruum, or render it less pellucid than before[5]. And other Instances there are, that oftentimes great quantities of Opake Matter are sustain'd in Fluids, without considerably striking the Eye, or being perceiv'd by it. So that were there Water any where found so pure, that the quickest Eye could discover in it no terrestrial Intermixture; that would be far short of a Proof, that in reality there was none.
But after all, even the clearest Water is very far from being pure and wholly defecate, in any part of the World that I can learn. For ours here, I have had an Opportunity of examining it over a good part of England; and cannot say I ever met with any, that, however fresh and newly taken out of the Spring, did not exhibit, even to the naked Eye, great numbers of exceeding small terrestrial Particles disseminated through all parts of it. Thicker and crasser Water exhibits them in still greater Plenty.
These are of two general kinds. The one a vegetable terrestrial Matter, consisting of very different Corpuscles; some whereof are proper for the formation and increment of one sort of Plant, and some of another; as also some for the Nourishment of one part of the same Plant, and some of another. The other kind of Particles sustain'd in Water are of a Mineral Nature. These likewise are of different sorts. In some Springs we find common Salt, in others Vitriol, in others Alum, Nitre, Sparr, Ochre, &c. nay, frequently several of these, or other Minerals, all in the same Spring; the Water as it drains and passes thorough the Strata of Stone, Earth, and the like, taking up and bearing along such loose Mineral Corpuscles, as it meets with in the Pores and Interstices of those Strata, and bringing them on with it quite to the Spring. All Water whatever is much charg'd with the Vegetable Matter, this being fine, light, and easily moveable. For the Mineral, the Water of Springs contains more of it than that of Rivers, especially when at distance from their Sources; and that of Rivers more than the Water that falls in Rain. This I have learn'd from several Trials, which I must not give Account of here; my Drift in this place being only to evince the Existence of Terrestrial Matter in Water.
Any one who desires farther Satisfaction in this, may easily obtain it, if he only put Water into a clear Glass Viol, stopping it close, to keep Dust and other exterior Matter out, and letting it stand, without stirring it for some Days: He will then find a considerable Quantity of terrestrial Matter in the Water, however pure and free it might appear when first put into the Viol. He will in a very short time observe, as I have frequently done, the Corpuscles that were at first, while the Water was agitated and kept in motion, separate, and hardly visible[6], by degrees, as the Water permits, by its becoming more still and at rest, assembling and combining together; by that means forming somewhat larger and more conspicuous Moleculæ. Afterwards he may behold these joining and fixing each to other, by that means forming large thin Masses, appearing like Nubeculæ, or Clouds in the Water; which grow more thick and opake, by the continual appulse and accretion of fresh Matter. If the said Matter be chiefly of the Vegetable kind, it will be sustain'd in the Water; and discover at length a green Colour, becoming still more and more of that Colour, I mean an higher and more saturate Green, as the Matter thickens and encreases. That this Matter inclines so much to that Colour, is the less strange, since we see so large a share of it, when constituting Vegetables wearing the same Colour in them. But if there be any considerable quantity of meer Mineral Matter in the Water, this, being of a greater specifick Gravity than the Vegetable, as the Particles of it unite and combine in such Number, till they form a Molecula, the Impetus of whose Gravity surpasses that of the Resistance of the Water, subsides a great deal of it to the bottom. Nor does it only fall down it self, but frequently entangling with the Vegetable Nubeculæ, forces them down along with it.
The Reason why Bodies, when dissolved and reduced to extreme small Parts, are sustain'd in Liquors that are of less specifick Gravity than those Bodies are, hath been pointed at by a late ingenious Member of this Society[7]. He is indeed far from having adjusted all the Momenta of this Affair; however it must be admitted, that, in the dividing or solution of Bodies, their Surfaces do not decrease in the same Proportion that their Bulk does. Now the Gravity of a Body, which is the Cause of its sinking or tendency downwards, is commensurate to its Bulk; but the resistance that the Liquor makes, is proportion'd, not to the Bulk, but to the Extent of the Surface of the Body immersed in it. Whence 'tis plain, a Body may be so far divided, that its Parts may be sustain'd in a Fluid, whose specifick Gravity is less than that of the said Body. Nay, 'tis Matter of Fact, that they frequently are so; and we daily see Menstrua supporting the Parts of Metals, and other Bodies, that are of six, ten, nay, almost twenty times the specifick Gravity of those Menstrua. And as the Parts of Bodies when divided, are thus supported in a Fluid; so when they occur and unite again, they must sink of course, and fall to the Bottom.
Upon the whole, 'tis palpable and beyond reasonable Contest, that Water contains in it a very considerable Quantity of terrestrial Matter. Now the Question is, to which of these, the Water, or the Earthly Matter sustain'd in it, Vegetables owe their Growth and Augment: For deciding of which, I conceive the following Experiments may afford some Light; and I can safely say, they were made with due Care and Exactness.
Anno 1691.
I chose several Glass Vials, that were all, as near as possible, of the same shape and bigness. After I had put what Water I thought fit into every one of them, and taken an Account of the weight of it, I strain'd and ty'd over the Orifice of each Vial, a Piece of Parchment, having an hole in the middle of it, large enough to admit the Stem of the Plant I design'd to set in the Vial, without confining or streightning it, so as to impede its Growth. My Intention in this, was to prevent the inclosed Water from evaporating, or ascending any other way than only through the Plant to be set therein. Then I made choice of several Sprigs of Mint, and other Plants, that were, as near as I could possibly judge, alike fresh, sound, and lively. Having taken the weight of each, I placed it in a Vial, order'd as above; and as the Plant imbib'd and drew off the Water, I took care to add more of the same from time to time, keeping an Account of the weight of all I added. Each of the Glasses were, for better distinction, and the more easie keeping a Register of all Circumstances, noted with a different Mark or Letter, A, B, C, &c. and all set in a Row in the same Window, in such manner that all might partake alike of Air, Light, and Sun. Thus they continued from July the Twentieth, to October the Fifth, which was just Seventy Seven Days. Then I took them out, weigh'd the Water in each Vial, and the Plant likewise, adding to its weight that of all the Leaves that had fallen off during the time it stood thus. And Lastly, I computed how much each Plant had gain'd; and how much Water was spent upon it. The Particulars are as follow.