Of course, when people see a wallflower rooted in the clefts of some old church tower, they don't jump at once to the inane conclusion that it is made of rock--that it derives its nourishment direct from the solid limestone; nor when they observe a barnacle hanging by its sucker to a ship's hull, do they imagine it to draw up its food incontinently from the copper bottom. But when they see that familiar pride of our country, a British oak, with its great underground buttresses spreading abroad through the soil in every direction, they infer at once that the buttresses are there, not--as is really the case--to support it and uphold it, but to drink in nutriment from the earth beneath, which is just about as capable of producing oak-wood as the copper plate on the ship's hull is capable of producing the flesh of a barnacle. Sundry familiar facts about manuring and watering, to which I will return later on, give a certain colour of reasonableness, it is true, to this mistaken inference. But how mistaken it really is for all that, a single and very familiar little experiment will easily show one. Cut down that British oak with your Gladstonian axe; lop him of his branches; divide him into logs; pile him up into a pyramid; put a match to his base; in short, make a bonfire of him; and what becomes of robust majesty? He is reduced to ashes, you say. Ah, yes, but what proportion of him? Conduct your experiment carefully on a small scale; dry your wood well, and weigh it before burning; weigh your ash afterwards, and what will you find? Why, that the solid matter which remains after the burning is a mere infinitesimal fraction of the total weight: the greater part has gone off into the air, from whence it came, as carbonic acid. Dust to dust, ashes to ashes; but air to air, too, is the rule of nature. It may sound startling--to Other People, I mean--but the simple truth remains, that trees and plants grow out of the atmosphere, not out of the ground. They are, in fact, solidified air; or to be more strictly correct, solidified gas--carbonic acid.