Page:The American Cyclopædia (1879) Volume II.djvu/89

ATLANTIC OCEAN 77 lished by the Dutch government and by the Scottish and Norwegian meteorolojjical socie- ties, the records of sea temperatures of some of the transatlantic steamship lines, those of the Danish ships sailing to Iceland and Green- land, collected by Admiral Irminger, and those of various arctic expeditions, furnished a consid- erable array of data. Of the twelve monthly charts contemplated, two only have been pub- lished, those for January and July. The chart for July exhibits the core of the Gulf stream at a temperature of 81 '5 extending northward as high as lat. 38, and with a temperature but slightly decreased as high as lat. 40, and as far east as Ion. 43. That it is not a mere drift is shown by the lower temperatures south of this tongue, which in January is shortened as might be expected. At Newfoundland the curves show the inroad made by the polar cur- rent, but in a less marked manner in winter than in summer. In July the polar current brings water at a temperature of 45 '6 down to lat. 50, while further east the Gulf stream water has still 65 in the same latitude. To the east of Newfoundland the isotherms set tow- ard the north with two bends more marked in summer than in winter. In July the isotherm of 54'5 advances toward Iceland and the Faroe islands to lat. 61. The wanner water follows not only the W. coast of Iceland, but passes round to the N. side of it, while on the E. and S. coast the polar current preponderates, pro- ducing a temperature lower by 5 or 6. Be- tween Iceland and the Faroe islands warm and cold bands of water alternate, the result of the struggle between the Gulf and polar streams, the latter carrying drift ice much further south in this region than anywhere else east of Ice- land, and reducing the temperature of the water at the Faroe islands to a lower point than it has on the W. coast of Iceland, where the winter climate is not as severe as it is in many parts of New England. The isotherm of 36, which touches Iceland in winter, extends at the same season beyond North cape ; the sea at Fruholm, North cape, is in January still at a mean temperature of 37'9. Ob- servations are wanting to show the further extension of the Gulf stream toward the north- east. It is met by a polar current running in the opposite direction, and cut by it into two branches, of which one runs along the W. side of Spitzbergen, the other eastward of Bear island. The further progress of this branch, which is the main one, is not known. The branch of the polar stream separating the two arms sets toward the coast of Greenland, where it is said to form a bight in the drift and field ice, reaching nearly to the coast. In high latitudes deep-sea temperatures show in many localities an anomaly in this, that the coldest are observed near the surface, and that there is an increase of temperature with depth. Observa- tions in the Antarctic ocean have shown the same phenomenon. It is frequently explained by comparison with the same phenomenon in fresh water, the maximum density of which is 7'2 higher than the freezing point. Although with regard to salt water the question appears still unsettled, the weight of evidence seems to point to an increase of density in the latter down to the freezing point. In that case the colder surface temperature might be attributed to the stratum of water from melting ice, float- ing over warmer layers because of less density. Some light has been afforded as to the course and origin of the currents in the northern seas by the driftwood and other materials thrown by them on the shores. The northern coast of Spitzbergen is covered with immense accumu- lations of driftwood, bark, pumice stone, &c. ; ' among them Torrel found a large bean of en- tada gigalobium, a product of tropical Ameri- ca found on all the shores washed by the Gulf stream, from Florida to Norway. These beans are found even in the Danish colonies on the W. coast of Greenland, where they are known under the name of vettenyrer or witches' kid- neys. The seeds of mucuna ureru and mimosa scandens are generally found with the former. The driftwood was pronounced by botanists to be nearly all Siberian larch, thus proving that the sea is open in summer as far as the mouths of the great Siberian rivers, and that in the locality mentioned the waters of the Gulf stream mix with those of the polar current. The saltness of the water in different parts of the ocean, as determined by Prof. Forchham- mer, was laid down on a chart by Dr. Peter- mann, and found to agree remarkably well with his temperature charts, the warmer or Gulf stream water being more salt than the colder or polar stream. From all the points discussed in his paper, Dr. Petermann draws the follow- ing conclusions: 1. The Gulf stream extends along the North American coast with a tem- perature of 77 and upward as far as lat. 37 ; a temperature in winter higher than the tem- perature of the air in Africa under the same latitude, and higher than the temperature of the water at any time under the equator. 2. The Gulf stream turns away from the Ameri- can coast in lat. 37 to 38 toward the east be- yond the banks of Newfoundland to Ion. 40 W., where it still has a temperature of about 75 in July and about 66 in January. From there it proceeds to the northeast, surround- ing Europe to the Arctic and the White sea with a permanent current of warm water, still having a temperature of 37'8 in a latitude in which in Asia and America the mercury remains frozen for months. 3. The velocity and strength of the stream are still imperfectly known. Findlay estimates the time for the water to travel from Florida to Europe at one or two years ; Dr. Petermann, at two months. 4. The Gulf stream must be a deep and volu- minous body of water, keeping away the polar ice from the coasts of Europe. The polar cur- rent presses at three places against it, E. of Newfoundland, E. of Iceland, and at Bear isl- and. 5. These polar currents make a much