In conclusion, we should wish to point out the important preservative influence exercised during the formation of dew. If the heat which is radiated from the earth, or from objects upon it, during a clear night, were not repaired in any way, the most serious injury would result to vegetation. For instance, if the sun raised no vapour during the day, so that when night came on the air was perfectly dry, and thus the radiant heat passed away into celestial space without compensation, not a single form of vegetation could retain its life during the bitter cold which would result. But consider what happens. The sun’s heat, which has been partly used up during the day in supplying the air with aqueous vapour, is gradually given out as this vapour returns to the form of water. Thus the process of refrigeration is effectually checked, and vegetation is saved from destruction. There is something very beautiful in this. During the day, the sun seems to pour forth his heat with reckless profusion, yet all the while it is being silently stored up; during the night, again, the earth seems to be radiating her heat too rapidly into space, yet all the while a process is going on by which the loss of heat is adequately compensated. Every particle of dew which we brush from the blades of grass, as we take our morning rambles, is an evidence of the preservative action of nature. _THE LEVELLING POWER OF RAIN._ It has been recognized, ever since geology has become truly a science, that the two chief powers at work in remodelling the earth’s surface, are fire and water. Of these powers one is in the main destructive, and the other preservative. Were it not for the earth’s vulcanian energies, there can be no question that this world would long since have been rendered unfit for life,—at least of higher types than we recognize among sea creatures. For at all times igneous causes are at work, levelling the land, however slowly; and this not only by the action of sea-waves at the border-line between land and water, but by the action of rain and flood over inland regions. Measuring the destructive action of water by what goes on in the lifetime of a man, or even during many successive generations, we might consider its effects very slight, even as on the other hand we might underrate the effects of the earth’s internal fires, were we to limit our attention to the effects of upheaval and of depression (not less preservative in the long run) during a few hundreds or thousands of years. As Lyell has remarked in his “Principles of Geology,” “our position as observers is essentially unfavourable when we endeavour to estimate the nature and magnitude of the changes now in progress. As dwellers on the land, we inhabit about a fourth part of the surface; and that portion is almost exclusively a theatre of decay, and not of reproduction. We know, indeed, that new deposits are annually formed in seas and lakes, and that every