VOL. XXI.J PHILOSOPHICAL TRANSACTIONS. 383 



several other plants thrive very much in water. The other is this : they take a 

 certain quantity of earth, and bake it in an oven, then tliey weigh it, and put 

 it into an earthen pot, and having watered it well, make choice of some fit 

 plant, which, being first carefully weighed, they set in it; there they let it 

 grow, continuing to water it for some time, till it is much increased in bulk. 

 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 con- 

 clude that it is not the earth, but water, that nourishes, and is turned into the 

 substance of the plant. I must confess I cannot see how this experiment can 

 ever be made witli the nicety and justness that is requisite, in order to build 

 upon it so much as these gentlemen do. And 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 increase entirely to that. Some waters are indeed so very clear and trans- 

 parent, that one would not easily suspect any terrestrial matter were latent in 

 them : yet they may be highly saturated with such matter, though the eye be 

 not presently able to discern it. It is true, earth is an opaque body, but it may 

 be so far dissolved, reduced to so extreme small particles, and these so diffused 

 through the watery mass, as not sensibly to impede vision, or render the water 

 much the less diaphanous. Silver is an opaque, and indeed a very dense body ; 

 and yet, if pure and perfectly dissolved in spirit of nitre, or aquafortis that is 

 rectified and thoroughly fine, it does not darken the menstruum, or render it 

 less pellucid than before. 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 is 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. Nor did I ever meet with any, however fresh and 

 newly taken out of the spring, that did not exhibit, even to the naked eye, 

 great numbers of small terrestrial particles, disseminated through all parts of it. 

 Thicker and crasser water exhibits them in still greater plenty. 



These particles are of two general kinds. The one a vegetable terrestrial 

 matter, consisting of very different corpuscles, some proper for the formation 

 and increment of one sort of plant, and some of others : as also some for the 

 nourishment of one part of the same plant, and some of another. The other 

 kind of particles, sustained in water, are of a mineral nature and also of dif- 

 ferent sorts. In some springs we find common salt, in others vitriol, alum, 

 nitre, spar, ochre, Sic. nay frequently several of these, or other minerals, all 



