Page:The American Cyclopædia (1879) Volume II.djvu/88

 ATLANTIC OCEAN straits of Florida into the gulf of Mexico, is rendered very improbable by Mr. Mitchell's observations cited above, and by the volume of water necessarily passing through these straits to supply as large a cross section as we find otf New York. It is much more probable that the cold water at the bottom of the gulf of Mexico reaches it by a much longer circuit, and perhaps a very small portion by the coun- ter currents at Cape Florida. The surface ve- locity of the Gulf stream appears to be vari- able, being probably aifected by the wind ; but although we have as yet no observations of the velocity at various depths, it is safe to assume a much greater constancy for the bulk of its waters. According to the chart of the Atlantic ocean published by the hydrographic office in Washington, the rate of the current in the straits of Florida is from 1 to 4 m. per hour ; in the narrows of Bernini, from 1 to 5 m. ; off the coast of Georgia, 1 J to 4 m. ; off Cape Fear and Cape Hatteras, 1 to 3f ; off Chesapeake bay, 4 m. ; and in the longitudes of Nova Scotia and Newfoundland, between 2 and 3 m. Mr. Findlay estimates it rather less: about 2f m. per hour in the narrows of Bernini, 2 off Charleston, H to 2 off Nantucket, and a little over 1 m. S. of the Newfoundland banks. Ac- curate observations at all seasons and at va- rious depths, though difficult to make, are very much needed. The further course of the Gulf stream after passing the banks of Newfound- land is involved in some doubt, as has been mentioned in speaking of the general sys- tem of currents of the Atlantic ocean. That water of a higher temperature than is due to the latitude reaches the northern and eastern shores of the Atlantic appears to be universally admitted. Capt. Strickland seems to have been the first to attribute this fact to the extension of the Gulf stream, and was supported in this opinion by the authority of Humboldt and Scoresby, the latter having made a large number of observations of tem- perature in the Arctic ocean. Leopold von Buch, struck during his travels along the coast of Norway with the luxuriance of the vegeta- tion in so high a latitude, the high level of the line of permanent snow, the freedom from ice of the harbor during the greater part of the winter, &c., attributed to the Gulf stream the office of bringing heat to these coasts ; and his reasoning appeared to Humboldt " perfectly convincing." Gen. Sabine, during one of his voyages for pendulum experiments, made nu- merous observations in the Gulf stream proper, and in its supposed extension across the ocean, and along the coasts of Europe, south of Eng- land and Africa, and was convinced that both were one and the same system. Rennel was the first to shake this belief, at the time almost universal, attributing the whole easterly and northerly movement of the waters to a super- ficial drift produced by the prevailing S. W. winds. It must be remarked that he ignores entirely the effect of the rotation of the earth, and of the heating and cooling of the waters at the equator and pole, joint causes which Arago was probably the first to exhibit, with- out, however, entering into their discussion. In very recent times the partisans of both opinions have shown a renewed activity, partly in connection with arctic, and partly with deep-sea explorations. It was in ref- erence to the former that Dr. Petermann gave his opinion as follows: "Instead of a weak and insignificant drift from Newfound- land toward Europe, as heretofore represent- ed, I consider the northern part of the Gulf stream one of the mightiest currents of the world, although comparatively slow, not very perceptible on the surface of the ocean, and therefore of no great moment to naviga- tion. I do so because ocean currents have to perform other functions than merely those of a strong surface stream. In that view I con- ceive the Gulf stream to be a deep, perma- nently warm current from Newfoundland to the coasts of France, Great Britain, Scandina- via, and Iceland, up to Bear island, Jan Mayen, and Spitzbergen; and along the western coa>t of the latter up to the 80th degree of north latitude, thence to Nova Zembla into the polar sea, passing the northernmost capes of Siberia and the New Siberian islands, where it appears on the charts as the Polynia of the Russians, ... its influence being felt perceptibly even as far east as Cape Yakan." Numerous opponents have risen against these assertions, among them Mr. Findlay, who contends that the Gulf stream proper has not sufficient width and depth to reach the coast of Europe ; that at its slow rate of progress it must lose all its heat during the passage; that after reaching Newfoundland it is totally annihilated by the Polar stream, and cannot be perceived beyond ; that the Gulf stream has nothing to do with the climate of northwestern Europe, which is affected only by the general drift of the North Atlantic ocean. To this Dr. Petermann re- plies that the Gulf stream is no doubt rein- forced by a drift corresponding to it in direc- tion, in the same way that a river is swelled by tributaries, without for all that losing its individuality and its name. Prof. Carpenter, in discussing the results of his deep-sea tem- perature observations, doubts if the Gulf stream sends any but a very small and super- ficial contribution to the northern seas, and is supported by the companion of his researches, Mr. Jeffreys, on zoological grounds, the latter rather premature, since we are still at the dawn of our knowledge of the deep-sea fauna. Dr. Petermann now took a very important step in the question ; the differences of opinion resting chiefly on belief and theory, he undertook to collect all the observations of temperature of the water in the North Atlantic and construct charts of isotherms for every month in the year. The large amount of materials buried in Maury's wind and current charts were in.-nk available by much labor ; the observations pub-