Since the most immediate Use of _Agriculture_, in feeding Plants, relates to their _Roots_, they ought to be treated of in the first Place. _Roots_ are very different in different Plants: But ’tis not necessary here to take notice of all the nice Distinctions of them; therefore I shall only divide them in general into two Sorts, _viz._ _Horizontal-Roots_, and _Tap-Roots_, which may include them all. All have Branchings and Fibres going all manner of ways, ready to fill the Earth that is open. But such _Roots_ as I call Horizontal (except of Trees) have seldom any of their Branchings deeper than the Surface or Staple of the Earth, that is commonly mov’d by the Plough or Spade. The Tap-Root commonly runs down Single and Perpendicular[1] reaching sometimes many Fathoms below. [1] In this manner descends the first Root of every Seed; but of Corn very little, if at all, deeper than the Earth is tilled. These first Seed-Roots of Corn die as soon as the other Roots come out near the Surface, above the Grain: and therefore this first is not called a Tap Root; but yet some of the next Roots that come out near the Surface of the Ground, always reach down to the Bottom of the pulveriz’d Staple; as may be seen, if you carefully examine it in the Spring time; but this first Root in Saint-foin becomes a Tap Root. This (tho’ it goes never so deep) has horizontal ones passing out all round the Sides; and extend to several Yards Distance from it, after they are by their Minuteness, and earthly Tincture, become invisible to the naked Eye. _A Method how to find the Distance to which_ Roots _extend Horizontally._ _Pl._ 6. _Fig._ 7. Is a Piece or Plot dug and made fine in whole hard Ground, the End _A_ 2 Feet, the End _B_ 12 Feet, the Length of the Piece 20 Yards; the Figures in the middle of it are 20 _Turneps_, sown early, and well ho’d. The manner of this Hoing must be at first near the Plants, with a Spade, and each time afterwards, a Foot farther Distance, till all the Earth be once well dug; and if Weeds appear where it has been so dug, hoe them out shallow with the Hand-Hoe. But dig all the Piece next the out Lines deep every time, that it may be the finer for the _Roots_ to enter, when they are permitted to come thither. If these _Turneps_ are all gradually bigger, as they stand nearer to the End _B_, ’tis a Proof they all extend to the Outside of the Piece; and the _Turnep_ 20 will appear to draw Nourishment from six Feet Distance from its Centre. But if the _Turneps_ 16, 17, 18, 19, 20, acquire no greater Bulk than the _Turnep_ 15, it will be clear, that their _Roots_ extend no farther than those of the _Turnep_ 15 does; which is but about 4 Feet. By this Method the Distance of the Extent of _Roots_ of any Plant may be discover’d.