The evidences of ordinary providence, which are common to geology and other sources of proof, I shall pass by; both because they are familiar to all, and because I have, in a former lecture, shown the existence and operation of the present laws of nature in all past ages. But there is one feature of the past condition of the world taught by geology to which I would call your attention, as exhibiting a more impressive view of the wisdom and skill of ordinary providence than almost any other department of nature presents. When the heavenly bodies are once put under the control of the two great forces that guide them, viz., the centrifugal and centripetal, we see no reason why they may not move on forever in their accustomed paths. But the two great agents of geological change, fire and water, have an aspect of great irregularity and violence, and are apparently less under the control of mathematical laws. In the mighty intensity of their action in early times, we can hardly see how there could have been much of security or permanence in the state of the globe, without the constant restraining energy of Jehovah. We feel as if the earth's crust must have been constantly liable to be torn in pieces by volcanic fires, or drenched by sweeping deluges. And yet the various economies of life on the globe, that have preceded the present, have all been seasons of profound repose and uniformity. The truth is, these mighty agencies have been just as much under the divine control as those which regulate the heavenly bodies; and I doubt not but the laws that regulate their action are as fixed and mathematical as those which guide the sun, moon, and planets. Still, it must have required infinite wisdom and power so to arrange the agencies of nature that the desolating action of fire and water should take place only at those epochs when every thing was in readiness for the ruin of an old economy and the introduction of a new one. Geological agencies differ from astronomical in this--that the former must be allowed an irregular action within certain limits; whereas the latter act with unvarying uniformity in all circumstances. If the former had not some room for irregular action, they would not act at all; but if allowed too much liberty, they will destroy what they were intended to preserve. And God does restrain, and always has restrained them, just at the point where desolation would be the result of their more powerful operation. I do not, indeed, contend that it requires more power or wisdom to bind those mighty agencies within proper limits than to control the heavenly bodies. But to our limited faculties it certainly seems a more difficult work; and, therefore, the geological history of the globe gives us a more impressive idea of the ordinary providence of God than we see in the calm and uniform movements of nature around us. _In the second place, geology furnishes us with some very striking examples of miraculous providence._