Изображения страниц
PDF
EPUB
[ocr errors]

hieves the prospect, wherein floats the wreck of the ice; reduced apparently to a small fraction of its original bulk.

The Captain was now called upon.deck, and Dr. Walker observed, " that ice was an article they were not in danger of wanting, though there are countries where from its scarcity ice is a luxury. In all hot climates ice is made." “ Made!” ejaculated Edward. “ Yes," replied the doc. tor. The greatest degrees of heat which are known, have been produced by concentrating the solar rays with a mirror, or lens, or by supplying a blow-pipe with oxygen gas. A very great degree of cold is produced by mixing snow with certain salts. The best salt for this purpose, is muriat of lime. If this be mixed with dry, light snow, and stirred well together, the cold produced will be so intense, as to freeze mercury in a few minutes. Salt and snow also produce a great degrec of cold.

“ Evaporation likewise produces cold. The method of making ice artificially in the East Indies, depends upon this principle. The ice-makers at Benares dig pits in large open plains, the bottom of which they strew with sugar-canes, or dried stems of maize, or Indian corn. Upon this bed they place a number of unglazed pans, made of so porous an earth, that the water oozes through their substance. These pans are filled towards evening, in the winter season, with water which has been boiled, and till unning, when more or less ice is found in them, according to the temperature of the air ; there being more formel in dry and warm weather, than in cloudy weather, though it may be colder to the human body.

Every thing in this operation is calculated to produce cold by evaporation ; the beds on which the pans are placed, suffer the air to have a free passage to their bottoms, and the pans constantly oozing out water to their external surface, are cooled by the evaporation of it.

“ In Spain, they use a kind of earthen jars, called buxaros, the earth of which is so porous, being only half-baked, that the outside is kept moist by the water which filters through it; and, though placed in the sun, the water in the jar becomes as cold as ice.

“ It is a common practice in China, to cool wine, or other liquors, by wrapping a wet cloth round the bottle, and hang. ing it up in the sun. The water in the cloth evaporates, anıl thus cold is produced.

ne left in that situation

" Ice may be produced at any time, by the evaporation of eller.

“ Professor Leslie has lately discovered that porphyritic trap, pounded and dried, will absorb one-tenth part of its weight of moisture, and can hence be easily made to freeze the eighth part of its weight of water. In hot countries the powder will after each process recover its power by drying in the sun.

This curious and beautiful discovery of artificial congelation, will therefore produce ice in the tropical climes, or even at sea, with very little trouble, and no sort of risk or inconvenience.

“ And now my dear Edward, you are already convinced of the wonderful power of chemistry. This one discovery which enables man in the hottest climate, even in the torrid zone, to compose artificially, and by such a simple process the product of the frigid zones is but a single instance, but it is sufficient to rank that noble science among one of the most important to man. Even in our every day meals, our tea, our coffee, every process of cookery, of medicine, in short, al. most all the operations of nature and art, are carried on by the means either of chemical, electric, or magnetic processes, with all of which I wish you to be acquainted in some degree:

SECTION IV.

THE WHALE FISHERY.

The Captain had now returned to the cabin, and Edward asked him “ in what latitude are whales most generally found ?

The CAPTAIN.- .“ The place where whales occur in the greatest abundance, is generally found to be in the 78th or 79th degree of north latitude, though from the 72d to the 81st degree they have been met with. They seem to prefer thiose situations which afford them the most secure retreats. Among the ice, they have an occasional shelter ; but so far as it is permeable, the security is rather apparent than real. That they are conscious of its affording them shelter, we can readily perceive, from observing that the course of their flight when scared or wounded, is generally towards the nearest or most compact ice. At one time, their favourite haunt is amidst the huge and extended masses of the field ice; at another, in the open seas adjacent. Sometimes the majority of the whales inhabiting those seas, seem collected within a small and single circuit; at others, they are scattered in va. rious hordes, and numerous single individuals, over an amazing extent of surface. To discover and reach the haunts of the whale, is an object of the first consideration in the fishery, and occasionally the most difficult and laborious to accomplish. In close seasons, though the ice joins the south of Spitzbergen, and thereby forms a barrier against the fishingstations, yet this barrier is often of a limited extent, and terminates on the coasts of Spitzbergen in an open space, either forming, or leading to, the retreat of the whales. Such space is sometimes frozen over until the middle or end of the month of May, but not unfrequently free of ice. The barrier here opposed to the fisher, usually consists of a mass of ice from 20 to 30 or 40 leagues across in the shortest diameter. It is generally composed of packed ice, and often cemented into a continuous field by the interference of bay ice, which incredibly augments the difficulty of navigating among it.

“ As the time that can be devoted to the whale-fishery, is, by the nature of the climate, limited to three or four months in the year, it is of importance to pass this barrier of ice as early as possible in the season. The fisher here avails himself of every power within his command. The sails are expanded in favourable winds, and withdrawn in contrary breezes. The ship is urged forward amongst the drift ice through the force of the wind, assisted by ropes and saws.Whenever a vein of water, as it is called, appears in the required direction, it is if possible attained. It always affords a temporary relief, and sometimes a permanent release, by extending itself through intricate mazes, amidst ice of various descriptions, until at length it opens into the desired place, void of obstruction, and the retreat of the whales.

“ The formidable barrier before described, is regularly encountered on the first arrival of Greenland ships in the month of April, but is generally removed by natural means as the season advances. However extensive, huge, and compact it may be, it is usually found separated from the land, and divided asunder by the close of the month of June ; and hence it is, that however difficult and laborious may have been the ingress into the fishing country, the egress is commonly effected without particular inconvenience.

[ocr errors]

" That the ice should envelope the whole coasts of Spitz. bergen in the winter season, and expose the western shore about the month of June; that the ocean should be almost annually navigable on the meridians of 5° to 10° E., to the 80th degree of north latitude, whilst the ice in every other part of the world, can rarely be penetrated beyond the 74th degree, are facts highly curious, and certainly worthy of con. sideration.

“ In the month of May, the severity of the frost relaxes, and the temperature occasionally approaches within a few degrees of the freezing point: the brine then exerts its liquefying energy, and destroys the tenacity of the bay ice, makes inroads in its parts by enlarging its pores into holes, diminishes its thickness, and, in the language of the whalefisher completely rots it. The packed drift ice is then loosed ; it submits to the laws of detached floating bodies, and obeys the slightest impulses of the winds or currents. The heavier having more stability than the lighter, an apparent difference of movement obtains among the pieces. Holes and lanes of water are formed, which allow the entrance and progress of the ships, without that stubborn resistance offered earlier in the spring of the year.

“ Bay ice is sometimes serviceable to the whale-fishers, in preserving them from the brunt of the heavy ice, by embedding their ships, and occasioning an equable pressure on every part of the vessel : but, in other respects, it is the greatesi pest they meet with in all their labours : it is troublesome in the fishery, and in the progress to the fishing ground; it is often the means of besetment, as it is called, and thence the primary cause of every other calamity. Heavy ice, many feet in thickness, and in detached pieces of from 50 to 100 tons weight each, though crowded together in the form of a pack, may be penetrated, in a favourable gale, with tolerable dispatch; whilst a sheet of bay ice, of a few inches only in thickness, with the same advantage of wind, will often arrest the progress of the ship, and render her in a few minutes immoveable. If this ice be too strong to be broken by the weight of a boat, recourse must be had to sawing, an operation slow and laborious in the extreme.

" When the warmth of the season has rotted the bay ice, the passage to the northward can generally be accomplished with a very great saving of labour. Therefore it was, the older fishers seldom or never used to attempt it before the 10th of May, and foreigners are in general late. Sometimes late arrivals are otherwise beneficial ; since it frequently happens, in close seasons, that ships entering the ice about the middle of May, obtain an advantage over those preceding them, by gaining a situation more eligible, on account of its nearness to the land. Their predecessors, meanwhile, are drifted off to the westward with the ice, and cannot recover their easting; for, they are encompassed with a large quantity of ice, and have a greater distance to go than when they first entered, and on a course precisely in opposition to the direction of the most prevailing winds. Hence it appears, that it would be economical and beneficial to sail so late, as not to reach the country before the middle of May, or to persevere on the seal catching stations until that time. There are, however, some weighty objections to this method. Open seasons occasionally occur, and great progress may sometimes be made in the fishery before that time.

“ The change which takes place in the ice amidst which the whale-fisher pursues his object, is, towards the close of the season, indeed astonishing.

“ As to the mode of catching, or rather killing whales, I need not describe that to you, for it is a subject upon which you are likely to be informed by sight."

SECTION V.

NATURAL PHENOMENA OF ICELAND, IT$ SPRINGS, &c.

As our travellers approached Iceland, they were glad to accept the captain's offer of warmer cloathing, and about the middle of July they anchored on the south-west shores of Iceland. From Ryhiabick, a town on this part of the coast, they proceeded across the valley of Ryham, which appeared to great advantage from a comparison with the dreary coun. try by which it was surrounded. The roads which led to it were composed of tracks made by the farmers in the lava and other volcanic matter. The valley of Ryham is richly cultivated and watered by a fertile stream, but what principally arrested the attention of our travellers was, the clouds of steam which ascended in various parts of the valley from the

a

« ПредыдущаяПродолжить »