Land-ice, of which both the ice-fields of the Arctics and glaciers consist, is produced by the slow and gradual transformation of snow into ice; and though the ice thus formed may eventually be as clear and transparent as the purest pond- or river-ice, its structure is nevertheless entirely distinct. We may trace these different processes during any moderately cold winter in the ponds and snow-meadows immediately about us. We need not join an Arctic exploring expedition, nor even undertake a more tempting trip to the Alps, in order to investigate these phenomena for ourselves, if we have any curiosity to do so. The first warm day after a thick fall of light, dry snow, such as occurs in the coldest of our winter weather, is sufficient to melt its surface. As this snow is porous, the water readily penetrates it, having also a tendency to sink by its own weight, so that the whole mass becomes more or less filled with moisture in the course of the day. Daring the lower temperature of the night, however, the water is frozen again, and the snow is now filled with new ice-particles. Let this process be continued long enough, and the mass of snow is changed to a kind of ice-gravel, or, if the grains adhere together, to something like what we call pudding-stone, allowing, of course, for the difference of material; the snow, which has been rendered cohesive by the process of partial melting and regelation, holding the ice-globules together, just as the loose materials of the pudding-stone are held together by the cement which unites them.