Such is the general view-point which we must adopt for the clearer comprehension of the details of observation. Of course, when speaking of the limit of the eternal snows, we refer only to the lower limit, that is to say, to the greatest elevation attained by the snow-line in the course of a single year. As for the upper limit, it entirely escapes us; for the summits of the loftiest mountains do not reach the atmospheric strata which, by virtue of their refraction, cannot contain any vesicular, aqueous, or condensable vapour.
The line of eternal snow which, at the poles, is found on the level of the ground, gradually rises as we approach the torrid zone, where it attains its maximum of elevation, from 13,000 to 17,000 feet. This phenomenon does not exclusively depend upon the geographical latitude, nor on the mean annual temperature of the locality: it is the result of an aggregate of diverse circumstances which we have not the space here to enumerate and discuss. We shall content ourselves with placing before the reader a table which will show the remarkable differences existing in the height of the perpetual snow-line in various places.
The Line of Perpetual Snow.
| Latitude. | Place. | Height of Snow-Line. |
|---|---|---|
| (Degs.) | ||
| 79 N. | Spitzbergen | 0 |
| 71 | Mageroe (Norway) | 2,350 |
| 70 to 60 | Norway (Interior of) | 3,500 to 5,100 |
| 65 | Iceland | 3,050 |
| 54 | Oonalashka (W. America) | 3,510 |
| 50 | Altai Mountains | 7,034 |
| 45 | Alps, The, N. declivity | 8,885 |
| 45 | Do., S. declivity | 9,150 |
| 43 | The Caucasus | 11,863 |
| 43 | The Pyrenees | 9,000 |
| 40 | Mount Ararat | 14,150 |
| 36 | Karakorum, N. side | 17,500 |
| 36 | Do., S. side | 19,300 |
| 36 | Kuen-luen, N. side | 15,000 |
| 35 | Do., S. side | 15,680 |
| 29 | Himalaya, N. side | 19,560 |
| 28 | Do., N. side | 15,500 |
| 17 | Cordilleras of Mexico | 14,650 |
| 13 | Ethiopian Mountains | 14,075 |
| 1 S. | Andes, in Quito | 15,680 |
| 16 | Do., in Bolivia, E. | 15,800 |
| 18 | Do., in Bolivia, W. | 18,400 |
| 33 | Do., in Chili | 14,600 |
| 43 | Do., in Patagonia | 6,300 |
| 54 | Strait of Magelhaens | 3,700 |
The Inhabitants of the Eternal Snows.
If men have the faculty of living under all climates, they make use of that faculty, as we know, with extreme reserve. They have never permanently inhabited the polar regions and the perpetually snowy summits of the mountains: it is only at intervals that a few pioneers have temporarily ventured thither. Starting from this fact, it was long believed that the zone of eternal snows was not inhabited by any living being. Even men of science admitted, as an article of faith, that where man could not fix his residence no animal could live. They made, however, a concession with respect to vegetables, and particularly as regarded the lichens and the mosses.
Well, observation and research conjointly, have erased this article of faith from the scientific code. It has been demonstrated that the icy regions, which man visits only at rare intervals, and where he sojourns but for a time, are the home of a certain number of animal species, more or less allied to the human species. The scientific exploration of these regions dates only from our own time. Spitzbergen, and the summit of the Alps,—such are our points of comparison.
It is difficult to conceive of anything more interesting than the historical exposition of the limited Fauna glacialis. First, let us take the discovery, comparatively recent, of a small rodent of the mouse order.
The Arvicola Leucurus, or Arctic Vole.