The Fourth Key of the Art is the entrance to the Second Work (and a reiteration in part and development of the foregoing): it is this which reduces our Water into Earth; there is but this only Water in the world, which by a bare boiling can be converted into Earth, because the Mercury of the Wise carries in its centre its own Sulphur, which coagulates it. The terrification of the Spirit is the only operation of this work. Boil them with patience; if you have proceeded well, you will not be a long time without perceiving the marks of this coagulation; and if they appear not in their time, they will never appear; because it is an undoubted sign that you have failed in some essential thing in the former operations; for to corporify the Spirit, which is our Mercury, you must have well dissolved the body in which the Sulphur which coagulates the Mercury is enclosed. But Hermes assumes that our mercurial water shall obtain all the virtues which the philosophers attribute to it if it be turned into earth.

An earth admirable is it for fertility — the Land of Promise of the Wise, who, knowing how to make the dew of Heaven fall upon it, cause it to produce fruits of an inestimable price. Cultivate then diligently this precious earth, moisten it often with its own humidity, dry it as often, and you will no less augment its virtue than its weight and its fertility.