“The frost of the succeeding winter may, I think, or may not, according to circumstances, penetrate through this layer, and solidify the water which it still retains in its interstices. If the winter set in with clear frosty weather, the penetration will probably take place; but if heavy snow occur at the commencement of winter, thus throwing a protective covering over the _névé_, freezing to any great depth may be prevented. Mr. Huxley’s idea seems to be quite within the range of possibility, that water-cells may be transmitted from the origin of the glacier to its end, retaining their contents always liquid.” We have thus briefly explained the process by which the mountain-snow changes its character, and, without actually melting and again freezing, the clearest ice may be formed from it, and go on accumulating, layer by layer, to an almost inconceivable extent. I allude now to mountains generally, for Greenland is not the only ice-factory of the world. That country has by no means a monopoly of the business, for nearly all parts of the earth have their great reservoirs of ice formed in the same manner from snow as the ice of Greenland, only with this difference, that the climate and the temperature necessary to the formation of glaciers from snow is higher above the sea-level in most other places than in Greenland. This climate and temperature are found above what is called the “snow-line”—that is to say, a line above which the snow does not disappear in the summer, and is therefore perpetual. At the equator this snow-line is of course higher than either to the north or south of that point. Towards both poles it descends steadily. For instance, on the two great equatorial mountains of Chimborazo and Popocatapetl, it is about 15,000 feet; above which all is ice and snow, and below which vegetation, beginning with an arctic type, passes through all the stages of climate, until at its base we find the rich vegetation of the tropics. Frequently glaciers from that upper region descend into the lower regions of vegetation to a considerable distance, but they are gradually melted away at the end, and can not, therefore, go beyond a certain line, terminating in, or rather changing from streams of ice to rivers of water. [Illustration] By the time we have gone so far north as Greenland we have discovered a great depression in this snow-line. In latitude 61° north, I have observed it to be 2400 feet. I have found it to be 1700 feet at latitude 69°; at latitude 78°, it was 500; and at between 80° and 82° the snow-line appeared to touch the sea, having no belt whatever for vegetation.