_Nitre_ is useful to divide and prepare the Food, and may be said to nourish Vegetables in much the same Manner as my Knife nourishes me, by cutting and dividing my Meat: But when _Nitre_ is apply’d to the Root of a Plant, it will kill it as certainly as a Knife misapply’d will kill a Man: Which proves, that _Nitre_ is, in respect of Nourishment, just as much the Food of Plants, as _White Arsenick_ is the Food of Rats. And the same may be said of Salts. _Water_, from _Van-Helmont_’s Experiment, was by some great Philosophers thought to be it. But these were deceived, in not observing, that Water has always in its Intervals a Charge of Earth, from which no Art can free it. This Hypothesis having been fully confuted by Dr. _Woodward_, no body has, that I know of, maintain’d it since: And to the Doctor’s Arguments I shall add more in the Article of Air. _Air_, because its Spring, _&c._ is as necessary to the Life of Vegetables, as the Vehicle of Water is; some modern Virtuosi have affirm’d, from the same and worse Arguments than those of the Water-Philosophers, that Air is the Food of Plants. Mr. _Bradley_ being the chief, if not only Author, who has publish’d this Phantasy, which at present seems to get Ground, ’tis fit he should be answer’d: And this will be easily done, if I can shew, that he has answer’d this his own Opinion, by some or all of his own Arguments. His first is, that of _Helmont_, and is thus related in Mr. _Bradley_’s general Treatise of _Husbandry and Gardening_, Vol. I. _p._ 36. ‘Who dry’d Two hundred Pounds of Earth, and planted a Willow of Five Pounds Weight in it, which he water’d with Rain, or distill’d Water; and to secure it from any other Earth getting in, he covered it with a perforated Tin Cover. Five Years after, weighing the Tree, with all the Leaves it had borne in that Time, he found it to weigh One hundred Sixty-nine Pounds Three Ounces; but the Earth was only diminish’d about two Ounces in its Weight.’ 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.