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THE CHALLENGER EXPEDITION.

1. Until a few years ago next to nothing was known of the bottom of the deep sea. Attention was first drawn to the subject when the idea was entertained of uniting Europe and America by telegraph. As ocean telegraphy was developed it became indispensable to ascertain the nature of the bottom on which the cables must rest, the temperature of the water through which they would have to pass, and the presence or absence of animals whose attacks must be provided against in the coating of the wires.

2. Naturalists, moreover, had seen cause to abandon the opinion formerly held that the bottom of the sea elsewhere than at a short distance from the land was a desolate waste. From time to time evidence was procured that in place of a desert, further investigation might prove it to be a vast field for zoological research, an undiscovered country from which countless living creatures might be obtained with organisms unlike what were known in any other domain of nature.

3. It was to satisfy inquiries proceeding from both these quarters that, on the 21st of December 1872, Her Majesty's ship Challenger, under the command of Captain Nares, steamed out of Portsmouth harbour on her memorable voyage of exploration round the world. The expedition was absent for 3 years and 5 months. They travelled nearly 70,000 miles, crossed and recrossed the Atlantic in every direction, and visited and explored all the other great ocean basins on the surface of the globe.

4. At intervals as nearly uniform as possible, three hundred and sixty-two different “observing stations,” as they were called, were established. At each of these careful investigation was made and registered regarding the depth of the ocean, a sample of the bottom was brought to the surface and analysed, the temperature at various depths was ascertained, and a small quantity of the bottom-water procured for examination. Specimens were also secured of the living creatures which people the ocean at different depths from the surface to the bottom.

5. For sounding purposes lines carried down through the water by means of heavy weights were employed. These lines were marked at every 25 fathoms. As each successive mark entered the water the time was carefully noted, and as soon as the slackening of the rope, shown by the increased time required for the running out of one of its divisions, indicated that the bottom had been reached, the paying out of rope was stopped and the depth was ascertained. With a weight of 3 cwts. attached the rope travelled downwards at a rate slightly exceeding 3 miles an hour, so that in the North Pacific, where the greatest depth was reached—about 6 miles—the rope must have been running for more than an hour and a half before it reached the bottom.

6. By the use of a long metal tube carried down by heavy weights attached to its upper extremity, which fell off when the point of the tube had passed into the ooze or mud, a small quantity of the bottom was procured. An ingeniously constructed bottle enclosed and secured sea-water at any depth that was desired. The floor of the ocean, moreover, on one occasion at a distance of 44 miles below the surface, was swept by dredges and trawls with 5 or 6 long loose bundles of hemp trailing behind, so that every living thing that could be entangled or caught was brought to the surface.

7. The Atlantic basin first received the attention of the

expedition. Sailing southwards by the coasts of Spain and Portugal as far as the Canaries, they then steered almost due west for the West India Islands. Thence they passed north to Halifax in Nova Scotia, south again to the Bermudas, across the Atlantic once more to Madeira, south along the west coast of Africa as far as Liberia, across to the coast of Brazil, and once again across to the Cape of Good Hope.

8. The greatest depth of water in the Atlantic they found to be at a point north of the Virgin Islands, where it reached 3875 fathoms, or rather less than 41 miles. The mean or average depth they ascertained to be 2000 fathoms, or a little over 2 miles. The Challenger's investigations, along with previous observations, have determined that the Atlantic has 3 great basins. One of them, the Eastern, extends from the west of Ireland nearly to the Cape of Good Hope, with an average depth along its middle line of 15,000 feet. The North-Western occupies the great eastern “bight" or bend of the American continent with an average depth of about 18,000 feet. The third is open to the south, and runs up the coast of South America as far as Cape Orange. The mean depth is 18,000 feet.

9. In the neighbourhood of the coast the deposits at the bottom consist of the debris washed down by rivers, or they are the result of the disintegration of the rocks of the coast-line. Down to a depth of 2000 fathoms the ocean-floor was found to be covered with a chalky deposit, largely formed of the broken shells of countless myriads of jelly-like creatures, so minute that millions of them would not weigh a single pound. The deepest depressions were covered with a red clay, the precise nature and origin of which cannot yet be said to be fully ascertained.

10. Once, but only once, had any of the naturalists of the expedition the opportunity of seeing in its full beauty and examining one of those wonderful creatures whose remains form the chief element of the chalky deposit. The animalcule was accidentally captured in the Pacific near the surface in calm weather. To the naked

eye

it seemed only a minute globular jelly-like mass with a red centre.

11. Under the microscope the shell was found to be extremely thin and glassy-like. Long spines about 15 times the diameter of the shell issued from it in all directions. The jelly-like part, almost all of which was outside the shell, was of a rich orange colour. Between the spines the space was filled up with a delicate froth of bubbles of uniform size," while along the spines themselves fine double threads of the transparent jelly, loaded with minute granules, "coursed up the one side and down the other." Not more for the important part it plays in the formation of the sea-bottom, than for “the complexity and the beauty of the organism with all its swimming or floating machinery in this expanded condition,” the animalcule excited the greatest interest.Compiled.

Questions on the lesson :—What practical necessity had arisen for a knowledge of the bed of the Ocean? In what other way had the subject become interesting? What was the date of the Challenger's setting out? How long was she absent? How far did she travel? What different points were enquired into at each of the "observing stations?” Explain how the sounding apparatus worked—that by which a specimen of the bottom, &c., was obtained? What facts were ascertained regarding the Atlantic? How is the specimen of the animalcules described whose remains form the chalky bed of the sea ?

THE CROSSING OF THE ALPS.—PART I.

THE FRENCH ARMY CROSSES.

1. On a comparison of all the passes, that of St. Bernard was considered the most favourable, but even here the engineer who had examined them thought the operation would be extremely difficult. “Difficult! is it possible ?” inquired Bonaparte. “I think so," replied the general of engineers, “but with extraordinary efforts.” “ Then let us start!” replied the first consul.

2. The choice of the passes over the mountains being fixed upon, it became necessary to attend to the operation itself—an operation which consisted in throwing sixty thousand men with all their appointments, to the other side of the Alps, destitute of beaten paths, over rocks and glaciers, at the worst season of the year, on the thawing of the snows. It is never a pleasant thing to have a park of artillery to drag along, since every gun requires several waggons after it. Thus for sixty pieces three hundred waggons were required, but in these high valleys, many of them sterile from the reign of an eternal winter, others scarcely extensive enough to furnish the means of livelihood to their scanty inhabitants, it is necessary to carry the bread for the troops, as well as the forage for the horses. The difficulty, therefore, was enormous. .

3. The first consul had taken care to obtain the assistance of the monks resident in the hospital of the Great St. Bernard. It is well known that this pious community had been established for ages in that fearful solitude, above the habitable region of the earth, in order to give their aid to travellers overtaken by storms or buried in the snow. The first consul, at the latest moment, had sent them a sum of money, in order that

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