"A slight modification of Johnstone's best and simplest plan, with a few sentences of explanation, will sufficiently elucidate Elkington's mystery, and will comprehend the case of all simple superficial springs. Perhaps in Agricultural Britain, no formation is more common than moderate elevations of pervious material, such as chalk, gravel, and imperfect stone or rock of various kinds, resting upon more horizontal beds of clay, or other material less pervious than themselves, and at their inferior edge overlapped by it. For this overlap geological reasons are given, into which we cannot now enter. In order to make our explanation simple, we use the words, gravel and clay, as generic for pervious and impervious material. [Illustration: Fig. 1.] "Our drawing is an attempt to combine plan and section, which will probably be sufficiently illustrative. From A to T is the overlap, which is, in fact, a dam holding up the water in the gravel. In this dam there is a weak place at S, through which water issues permanently (a superficial spring), and runs over the surface from S to O. This issue has a tendency to lower the water in the gravel to the line M _m_. But when continued rains overpower this issue, the water in the gravel rises to the line A _a_, and meeting with no impediment at the point A, it flows over the surface between A and S. In addition to these more decided outlets, the water is probably constantly squeezing, in a slow way, through the whole dam. Elkington undertakes to drain the surface from A to O. He cuts a drain from O to B, and then he puts down a bore-hole, an Artesian well, from B to Z. His hole enters the tail of the gravel; the water contained therein rises up it: and the tendency of this new outlet is to lower the water to the line B _b_. If so lowered that it can no longer overflow at A or at S, and the surface from A to O is drained, so far as the springs are concerned, though our section can only represent one spring, and one summit-overflow, it is manifest that, however long the horizontal line of junction between the gravel and clay may be, however numerous the weak places (springs) in the overlap, or dam, and the summit-overflows, they will all be stopped, provided they lie at a higher level than the line B _b_. If Elkington had driven his drain forward from B to _n_, he would, at least, equally have attained his object; but the bore-hole was less expensive. He escapes the deepest and most costly portion of his drain. At _x_, he might have bored to the centre of the earth without ever realizing the water in this gravel. His whole success, therefore, depended upon his sagacity in hitting the point Z. Another simple and very common case, first