Page:The American Cyclopædia (1879) Volume XIII.djvu/677

 POLAE SEAS 65T ery is to find winter quarters somewhere with- in Smith sound, and at such a distance from the entrance that it may be within reach of a third ship, which is to sail in 1877 if necessary, and form a depot somewhere near the mouth of the sound. The Alert is, if possible, to push on to some point further N., but not to winter at a greater distance than 200 m. from her con- sort. In the spring of 1876 the sledging expe- dition for the north pole will be sent out, and subsidiary expeditions be made for the explo- ration of the coast. Success in the spring of 1876 might enable the expedition to return in the course of that autumn ; but a second win- ter, and even another season of exploration, may become necessary. If it should appear impossible to extricate the ships from the ice in the summer of 1877, one or both would probably be abandoned, and the crews would fall back upon the relief ship to be sent out to the entrance of Smith sound. For an ex- cellent and detailed account of polar explo- ration since 1871, see Die Polarforschung der Gegenwart, by Friedrich von Hellwald, in the Deutsche Rundschau for November, 1874. II. ANTAECTIO OCEAN. The royal geographical society has fixed the limits of the Antarctic ocean arbitrarily at the south polar circle, which corresponds nearly with the average limit of the pack ice. Other limits based on isothermal conditions of the sea have been pro- posed, but observations are not yet sufficient in number to give satisfactory results. Much less is known of this sea than of the north polar sea, the totally unexplored regions in the two bearing the proportion of nearly three to one. Navigators who have penetrated into the ice are few, and the highest point reached by Sir James 0. Ross falls far short of the lat- itude reached by many of the northern expe- ditions. (See ANTARCTIC DISCOVERY.) Our older maps showed in this region an imagi- nary antarctic continent, which the progress of discovery has tended to diminish continual- ly ; we are still much in the dark with regard to the extent of the land seen, and much acri- monious discussion has taken place between the American, English, and French discover- ers. The discrepancies could probably be rec- onciled in a great measure by assuming that much of the land seen consisted of islands of no great extent, which have been erroneous- ly assumed to be parts of a continuous coast. Victoria Land, discovered by Ross, is probably the largest island actually seen ; mountains of 12,000 to 15,000 ft. were seen on it, the south- ernmost being the volcanoes Erebus and Ter- ror. The ice pack is encountered between lat. 60 and 70, and was supposed by Capt. Cook, who first saw it, to be impenetrable. But his successors since the time of Bellingshausen have found that during the southern summer it is in motion toward the north, and that af- ter penetrating it large spaces of open water are found, at times so extensive that no ice is in sight from the masthead. Capt. Ross, j after penetrating to lat. 78 10', was stopped j by a high barrier of apparently stationary ice. From all accounts, the antarctic ice seems to be much heavier and thicker than that at the north pole, but of its mode of formation we know but little. Immense fields are described with a flat surface, but terminated by vertical cliffs, generally about 150 ft. high, quite differ- ent from anything observed at the north. The ice drifts to the north further in the southern summer than in winter. According to Fitz Roy, who has collected a large number of ob- servations of drift ice, it is found in greatest abundance and further toward the equator in January than in any other month. The aver- age limits for the whole year within which drift ice and bergs are encountered with toler- able certainty are 45 S. in the middle and E. part of the Atlantic and the W. part of the Indian ocean, 54 in the middle part of the Pacific, 58 off Cape Horn, and 60 in the central part of the Indian ocean and W. part of the Pacific, or between the meridians of 70 E. and 170 W. With regard to quantity, it ap- pears that it is least in the seas S. of Australia and New Zealand, and greatest in the eastern Atlantic and western Indian ocean; but this result may be affected by the greater number of observations on record for the latter region. The extreme lowest latitudes at which drift ice has been encountered are 34 S. in the At- lantic and 40 in the Pacific. The influence of ocean currents is very plainly exhibited in the outline of the limits of drift ice. Thus at the S. extremity of America the Cape Horn cur- rent, joined to the Brazilian and La Plata cur- rents, repels the ice toward the east, keeping it off the Falkland islands ; but east of these the antarctic current carries it far into the At- lantic. At the cape of Good Hope the ice is carried into a point toward its W. end by the same current which here gives off the South African current. But immediately E. of the cape the united Mozambique and Madagascar warm currents repel the ice considerably fur- ther S. Again, S. of Australia and New Zea- land the combined S. and E. Australian cur- rents form a deep bend in the limiting line of the drift ice. Deep-sea temperatures were ta- ken by Sir James C. Ross, but with thermom- eters exposed to pressure and therefore not as trustworthy as the more recent though less numerous ones of the Challenger expedition, which gave 28 to 29 at the surface (32 near the pack), 29 at a depth of 40 to 300 fathoms, and below that 33 to 34. This warmer stra- tum prevented the obtaining of the true tem- perature at the bottom. With regard to the climate, observations, deficient as they are, still point conclusively to the fact that the winters are milder and the summers cooler than in the north polar regions, thus indicating a more maritime climate caused by a less amount of land. No land mammals are known to inhabit the islands of the far south, thus contrasting with the north polar regions, where large and