ICE IN THE ARCTIC REGIONS.

Bruce Herald, Volume XIII, Issue 1205, 21 May 1880, Page 5

ICE IN THE ARCTIC REGIONS.

* Liou'.en-uifc Karl Weyprecht has lately given to the public an interest' ng work relating to ice and its metamorphoses in the Polar regions, from which the following, as given by Professor 11. N. Mosely in ' Nature ' is taken : — As an example of the mighty size of the Polar glaciers, the parents of the icebergs, the author cites the Humboltlt glacier of Smith Sound, which, pushing itself into the Sea in Smith forms an unbroken ice coast line composed of perpendicular cliilVj 300 feet in height above the sea level and 60 miles in length, a single solid ice wall split only by vertical fissures. The fresh water ice is clear as crystal, and so hard that the Norwegian walrus hunters who run their small vessels in their voyages against all other ice obstacles, of whatever &ize, are careful not to charge even comparatively small pieces of this. This kind of ice U, however, scarce in the polar regions ; it is the third kind of ice,

that of salt water, or f field ice," which forms by far the greater part of floating ice, and with which the body is mainly concerned. The Tegetthoff was shut in for a year in field ice, andr the author watched the incessant changes \in the ice with great care throughout this period. A simple smooth sheet of sea water ice is no sooner formed than ,< it begins to be subjected to a variety of in- j fluences, which speedily* convert its smooth j expanse into complicated rugged surfaces covered with ridges, valleys, and irregularities of all kinds, render its thickness everywhere unlike, and split up with innumerable fissures. Most important amongst the causes of these changes are the variations of temperature to which the ice is exposed from the variation of that of the water below and the air above, and which are more or less local, and affect the ice differently whereever its thickness varies. From these differences of temperature ensue complicated strains in all directions, due to the unequal expansion and contraction of the mass, and the ice is rent by the tension j to these forces is added the pressure of surrounding ice fields, driven by the action of winds or currents ; long fissures are formed, the edges of which grind together with mighty force. After a while the edges "seperate, and the water between pulsates with tbe throbbing of tbe surrounding floes. Again they come, together, and forced one against the other with ever-increasing power, they are crushed and break up, huge blocks are piled above on the surface, rest at all angles upon one another and other hugh blocks are orced under the ice below. Hence the ice becomes ragged above, and by the freezing to it of the blocks forced under water, equally so below, the variation in thickness is increased, and with it the amount of strains caused by the variation of temperature. The drifting show hangs against the ridges and pinnacles on the surface, and forms banks and mounds which not only increase the effects due to temperature by protecting the areas on. which they lie from change, but also by their immense weight, combined with that of the projecting ice masses by which they are formed, press down the ice which supports them, while the blocks below in other regions press it up. Throughout the mass gravity acts as a disturbant, no part being water borne at its natural level, the mass is strained, and gives way in all directions, and fresh complications ensue. All these changes are accompanied by a noise. The unlucky prisoner in the field ice dui'ing the imposing unbroken loneliness of the long Arctic night, when the wind is calm, can hear the crackle of the enow under the stealthy tread of the polar bear at an astonishing distance, and hear what a man, speaking loud, says at 1000 metres distance. It can, therefore, be well understood bow the sound of the ice pressures must travel to his ears from enormous distances. " Sometimes," the author writes, " the noise of the ice movements was scarcely to be heard — a mere murmur — and came to our ears as does the play of the waves on a steep coast from the far, far distance. Sometimes it hummed and roared closer to us, as if a whole column of heavily laden waggons were beiDg drawn over the uneven ice surface." In the sound were combined all manner of noises caused by cracking, grinding, falling of blocks, crushing, and many other phenomena of ice life. "It is astonishing how far and how clearly every noise is conducted in the ice. The noise at the very margin of the field on which we were seemed to occur immediately at our feet If we placed our ears to the ice the sound was heard so loudly that we might have expected the ice to open at our feet the next moment. The whole dry ice covering was a vast sounding board. Whenever, as I lay down to sleep, I placed my ear against the dry wooden ship's side, I heard a humming and buzziDg which was nothing else but the sum of all the noises which occurred in the ice at a great distance from the ship. A curious fact is described by the author, that the surface of an expanse of young salt water ice on which no snow has jet fallen is soft, so that the footstep is impressed upon its white covering as in melting snow. This is to be observed even at a temperature of 40deg. O. The unfrozen fluid is not water, but a concentrated solution of salt thrown out by the freezing of the ice beneath. When summer begins, the thawing that occurs is very local and unequal. Any dark body, such as a heap of ashes, or j the droppings of bears, eats its way into the snosv, absorbing the rays of heat which are reflected off agaii: by the general white surface. The bear droppings eat their ' way into the snow, and then into the ice, and ihe conical hole thus formed fills itself with water. It may, at last, eat its way right through the ice where uot very thick. Thus are formed the greater part of those holes in drifc ice which are usually ascribed to seals. The author never saw a seal's hole in winter. A number of interesting experiments were made on ice phenomena. For example, on sth March, a cube of ice was sunk under the ice field to a depth of about five meters. After the lapse of 2-i hours it was found that a crust of new ice had formed itself over it about 1 cm. thick. This was caused by the low temperature of the block itself and, from a similar cause, ice crystals had formed be-* tween the edges of the hole, owing to the coldness of its walls. On 10th March very, little increase in the added layer of ice on the cube was to be observed. On 20th March this newly-formed ice was found to be softened, so that it was easily impressed by the finger ; by 2nd April it had become harder again, though porous and apparently a little increased. From thence onward the block dwindled regularly, especially on that part of its surface !

wjb'ich was turned upward j on 18fch July itwas only a third of its original size ; nevertheless, the hole through which it was sunk had, during the last period, become entirely closed by young ice at its lower margin. This experiment shows the loss^of &g from below by the action of the»warmm of the water. The author concludes irom his experiments and measurements that compact salt water ice can never "attain a greater thickness than 10 meters. Icebergs are subjected to disintegration after somewhat the same manner as rocks so commonly are. They are full of crevices, into which the water formed by melting penetrates. In winter this water freezes, and by its expansion all through the glacier a rupture of the mass ensues. "It is highly probable that most of the icebergs afloat in winter are in such a condition that a very slight cause is sufficient to make them burst because of their state of interial tension. . . Every Polar traveller can tell how a shot, the driving in of an ice anchor, or any other sudden vibration, has brought about the catastrophe ; cases have even occurred in which the sound of the voice alone was sufficient. An iceberg is always an unpleasant neigh« bour." So many are the causes which tend to destroy icebergs that the author con» eludes " no berg exists which could withstand them more than ten years, and that commonly the life of a berg is much shorter." However that may be, doubtless the much larger Antarctic bergs last very much longer, as must necessarily occur because of the much greater uniformity of the climate to which they are exposed. With regard to glaciers, the author quotes an interesting observation of Kane's to the effect that even in lat. 78 deg. 20sec. during the entire winter, bow-ever low be the temperature, the glacier streams never dry up. The melting which supplies them with water can only derive its requisite heat from the friction of the ice masses. The chapter on the ice movements is full of interest. Every field acted on by winds and currents has its own peculiar velocity, depending on the dimensions of the irregularities above and those of the resistances below, in which no two fields are alike. From these differences of velocity arise the irresistible pressures between contiguous fields. The iceberg deeply sunk drifts but slowly, while the ice field may travel very fast. If the field catches up a berg in its course, it is broken and torn by the berg ; and as it proceeds on its course its broken fragments are piled up block upon block ou the coast of the iceberg. To a casual observer it appears as though the iceberg, driven, by a counter current below, were being forced in the opposite direction to the field, so as to plough it up. Many groundless accounts of the existence of such counter currents thus observed have been circulated. Another cause of pressure between ice fields is that, owing to the irregularities on their surfaces, they are twisted round by the action of the wind, which takes bold more on some regions than others. Every field is differently thus acted upon for each direction of the wind. A similar effect is caused by the currents beneath acting upon the irregularities of the under surface. So various are the movements in the ice fields that even, when the ice lies all the while closed, it is very seldom that any two pieces remain for any length of time in the same position alongside one another. Two ships beset together by the ice are sure sooner or later to be separated.