5. Earth. That which nourishes and augments a Plant is the true Food of it.
Every Plant is Earth, and the Growth and true Increase of a Plant is the Addition of more Earth.
Nitre (or other Salts) prepares the Earth, Water and Air move it, by conveying and fermenting it in the Juices; and this Motion is called Heat.
When this additional Earth is assimilated to the Plant, it becomes an absolute Part of it.
Suppose Water, Air, and Heat, could be taken away, would it not remain to be a Plant, tho’ a dead one?
But suppose the Earth of it taken away, what would then become of the Plant? Mr. Bradley might look long enough after it, before he found it in the Air among his specific or certain Qualities.
Besides, too much Nitre (or other Salts) corrodes a Plant; too much Water drowns it; too much Air dries the Roots of it; too much Heat (or Fire) burns it; but too much Earth a Plant never can have, unless it be therein wholly buried; and in that Case it would be equally misapply’d to the Body, as Air or Nitre would be to the Roots.
Too much Earth, or too fine, can never possibly be given to Roots; for they never receive so much of it as to surfeit the Plants, unless it be depriv’d of Leaves, which, as Lungs, should purify it.
And Earth is so surely the Food of all Plants, that with the proper Share of the other Elements, which each Species of Plants requires, I do not find but that any common Earth will nourish any Plant.
The only Difference of Soil[7] (except the Richness) seems to be the different Heat and Moisture it has; for if those be rightly adjusted, any Soil will nourish any Sort of Plant; for let Thyme and Rushes change Places, and both will die; but let them change their Soil, by removing the Earth wherein the Thyme grew, from the dry Hill down into the watry Bottom, and plant Rushes therein; and carry the moist Earth, wherein the Rushes grew, up to the Hill; and there Thyme will grow in the Earth that was taken from the Rushes; and so will the Rushes grow in the Earth that was taken from the Thyme; so that ’tis only more or less Water that makes the same Earth fit either for the Growth of Thyme or Rushes.