On this Experiment Mr. Bradley grounds his Airy Hypothesis. But let it be but examined fairly, and see what may be thence inferr’d.
The Tin Cover was to prevent any other Earth from getting in. This must also prevent any Earth from getting out, except what enter’d the Roots, and by them pass’d into the Tree.
A Willow is a very thirsty Tree, and must have drank in Five Years time several Tuns of Water, which must necessarily carry in its Interstices a great Quantity of Earth (probably many times more than the Tree’s[5] Weight, which could not get out, but by the Roots of the Willow.
[5]The Body of an Animal receives a much less Increase in Weight than its Perspirations amount to, as Sanctorius’s Static-Chair demonstrates.
Therefore the Two hundred Pounds of Earth not being increased, proves that so much Earth as was poured in with the Water, did enter the Tree.
Whether the Earth did enter to nourish the Tree, or whether only in order to pass through it (by way of Vehicle to the Air), and leave the Air behind for the Augment of the Willow, may appear by examining the Matter of which the Tree did consist.
If the Matter remaining after the Corruption or Putrefaction of the Tree be Earth, will it not be a Proof, that the Earth remained in it, to nourish and augment it? for it could not leave what it did not first take, nor be augmented by what pass’d through it. According to Aristotle’s Doctrine, and Mr. Bradley’s too, in Vol. I. pag. 72. “Putrefaction resolves it again into Earth, its first Principle.”
The Weight of the Tree, even when green, must consist of Earth and Water. Air could be no Part of it, because Air being of no greater specific Gravity than the incumbent Atmosphere, could not be of any Weight in it; therefore was no Part of the One hundred Sixty-nine Pounds Three Ounces.
Nature has directed Animals and Vegetables to seek what is most necessary to them. At the Time when the Fœtus has a Necessity of Respiration, ’tis brought forth into the open Air, and then the Lungs are filled with Air. As soon as a Calf, Lamb, &c. is able to stand, it applies to the Teat for Food, without any Teaching. In like manner Mr. Bradley remarks, in his Vol. I. pag. 10. ‘That almost every Stem and every Root are formed in a bending manner under Ground; and yet all these Stems become strait and upright when they come above-ground, and meet the Air; and most Roots run as directly downwards, and shun the Air as much as possible.’
Can any thing more plainly shew the Intent of Nature, than this his Remark does? viz. That the Air is most necessary to the Tree above ground, to purify the Sap by the Leaves, as the Blood of Animals is depurated by their Lungs: And that Roots seek the Earth for their Food, and shun the Air, which would dry up and destroy them.