IN CLOUDS AND RIVERS, ICE AND GLACIERS. 



119 



clivity in a series of great transverse ridges. 

 At the base of the fall, the chasms are 

 closed, but the ridges in part remain, forming 

 protuberances, which run like vast wrinkles 

 across the glacier. These protuberances are 

 more and more bent because of the quicker 

 motion of the centre, and the depressions be- 

 tween them form receptacles for the fine 

 mud and ddbris washed by the little rills from 

 tLe adjacent slopes. 



'337. The protuberances sink gradually 

 through the wasting action of the sun. so 

 that long before Tre'laporte is reached they 

 have wholly disappeared. Not so the dirt of 

 which they were the collectors : it continues 

 to occupy, in transverse bands, the flat sur- 

 face of the glacier. At Trelaporte, moreover, 

 where the valley becomes narrow, the bands 

 are much sharpened, obtaining there the 

 character which they afterwaul preserve 

 throughout the Mer de Glace. Other glaciers 

 with cascades also exhibit similar bands. 



49. SEA ICE AND ICEBERGS. 



338. We are now equipped intellectually 

 for a campaign into another territory. Water 

 becomes heavier and more difficult to freeze 

 when salt is dissolved in it. Sea water is 

 therefore heavier than fresh, and the Green- 

 land Ocean requires to freeze it a temperature 

 3 degrees lower than frish water. When 

 concentrated till its specific gravity reaches 

 1.1045, sea water requires for its congelation 

 a temperature 1S degrees lower than the or- 

 dinary freezing-point. 



339. But even when the water is saturated 

 with salt, the crystallizing force studiously 

 rejects the salt, and devotes itself to the con- 

 gelation of the water alone. Hence the ice 

 of sea water, when melted, produces fresh 

 water. The only saline particles existing in 

 such ice are those entangled mechanically in 

 its pores. They have no part or lot in the 

 structure of the crystal. 



340. This exclusiveness, if I may uso the 

 term, of the water molecules ; this entire re- 

 jection of all foreign elements from the edi- 

 fices which they build, is enforced to a sur- 

 prising degree. Sulphuric acid has so strong 

 an affinity for water that it is one of the most 

 powerful agents known to the chemist for 

 the removal of humidity from air. Still, as 

 shown by Faraday, when a mixture of sul- 

 phuric acid and water is frozen, the crys- 

 tal formed is perfectly sweet and free from 

 acidity. The water alone has lent itself to 

 tho crystallizing force. 



341. Every winter in the Arctic regions 

 the sea freezes, roofing itself with ice of 

 enormous thickness and vast extent. By the 

 summer heat, and the tossing of the waves, 

 this is broken up ; the fragments are drifted 

 by winds and borne by currents. They 

 clash, they crush each other, they pile them- 

 selves into heaps, thus constituting the chief 

 danger encountered by mariners in the polar 

 seas. 



342. But among the drifting masses of flat 

 sea-ice, vaster masses sail, which spring from 

 * totally different source These are the lc&- 



bergs of the Arctic seas. They rise some- 

 times to an elevation of hundreds of fet't 

 above the water, while the weight of ice sub- 

 merged is about seven times that seen above. 



343. The first observers of striking natural 

 phenomena generally allow wonder and im- 

 agination more than their due place. But to 

 exclude all error arising from this cause, I 

 will refer to the journal of a, cool and intrepid 

 Arctic navigator, Sir Leopold McClintock. 

 He describes an iceberg 250 feet high, which 

 was aground in 500 feet of water. This 

 WoUld make the entire height of the berg 75$ 

 feet, not an unusual altitude for the greater 

 icebergs. 



344. From Baffin's Bay 1 hese mighty masses 

 come sailing down through Davis' Straits into 

 the broad Atlantic. A vast amount of heat 

 is demanded for the simple liquefaction of ice 

 ( 48) ; and the melting of icebergs is on this 

 account so slow, that when large they some- 

 times maintain themselves till they have been 

 drifted 2000 miles from their place of birth. 



345. What is their origin? The Arctic 

 glaciers. From the mountains in the interior 

 the indurated snows slide into the valleys and 

 fill them with ice. The glaciers thus formed 

 move like the Swiss ones, incessantly down- 

 ward. But the Arctic glaciers reach the sea, 

 enter it, often ploughing up its bottom into 

 submarine moraines. Undermined by the 

 lapping of the waves, and unable to resist the 

 strain imposed by their own weight, they 

 break across, and discharge vast masses into 

 the ocean. Some of these run aground on 

 the adjacent shores, and often maintain 

 themselves for years. Others escape south- 

 ward, to be finally dissolved in the warm 

 waters of the Atlantic. The first engraving 

 on this pasje is copied from a photograph 

 taken by Mr. Bradford during a recent ex- 

 pedition to the Northern seas. The second 

 represents a mass of ice upon the Glacier 

 des Bossons. Their likeness suggests their 

 common origin. 



50. THE ^GGISCHHORN, THE MABGELIN 

 AND ITS ICEBEHGS. 



346. I am, however, unwilling that you 

 should quit Switzerland without seeing such 

 icebergs as it can show, ?nd indeed there are 

 other still nobler glaciers than the Mer de 

 Glace with which you ought to be ac- 

 quainted. In tracing the Rhone to its 

 source, you have already ascended the valley 

 of the Rhone. Let us visit it again together ; 

 halt at the little town of Viesch, and go from 

 it straight up to the excellent hostelry on the 

 slope of the ^Eggischhorn. This we shall 

 make our headquarters while we explore 

 that monarch of European ice-streams the 

 great Aletsch glacier. 



347. Including the longest of its branches, 

 this noble ice-river is about twenty miles 

 long, while at the middle of its trunk it meas- 

 ures nearly a mile and a quarter from side 

 to side. The grandest mountains of the Ber- 

 nese Oberland, the Jun.irf'rau, the Monch, the 

 Trusberg, the Aletschhorn, the Breithorn, 

 the Gletscherhorn, and many another noble 



