The universal geography : earth and its inhabitants

GULF STREAM— TEMPERATURE.and so dense that one end of the vessel was invisible at the other. During themonth of June they never once beheld a blue patch of sky. On the other hand,the atmosphere in tbese seas is generally calm, and the storms are seldom veryfierce,although the low temperature makes them at times seem more violent thanthey really are. Most of them are of short duration, and all end invariably inabsolute stillness.*The temperature of the surface waters has enabled meteorologists to determinethe outward limits of the North Atlantic warm current. Thermometricalcalculations made in the deep waters have also revealed thenormal depth of the current in the various seas that havebeen scientifically explored. But such delicate and costlyobservations have hitherto been necessarily restricted to a verysmall portion of the oceanic area. Till quite recently ourinformation on the subject was limited to the revelations ofWyville Thomson and Carpenter, aided by other naturalistswho took part in the explorations of the Lightning andPorcupine in 1868 and 1869. Since then these seas havebeen again explored under the direction of Swedish andNorwegian scientists, and in 1877 nearly the whole of theNorwegian waters were visited by the meteorologist Mohnin the Voringen, who has thus been enabled to draw up anisothermal chart based on hishis predecessors.own observations and those ofThe observations having been made during the fine season,when the surface waters are exceptionally heated by therays of the summer sun, the hitherto observed surfacetemperature was always high, fulling rapidly in the deeperstrata for about 55 fathoms. But the reverse was found tobe the case in winter, when the surface was cool. Thetemperature was then observed to rise to a stratum of normalheat indicating the mean of the year, and found at a depth ofnot less than 55 fathoms.But at this point the local climaticinfluences cease, and the plummet penetrates the ocean depthsin a temperature unaffected by the sudden changes of theseasons. Below the zone changing from winter to summer,Fig. 4. Temperatureor the Ocean WestOF RoCKALL.the thermometer indicates a steady diminution of heat, the strata growing colder andcolder without any reaction whatsoever.The lowest temperature thus correspondswith the lowest depth;yet it was nowhere found to reach the freezing point, whichfor sea-water with a mean saline density is 25° 4' Fahr.J The thermometricalsoundings of Sir "Wyville Thomson and his associates have thus definitely refutedthe hypothesis of Sir James Boss, who supposed that the bottom of the ocean from* Von Freeden, in Petermann's Mittheilungeii, iv. 1S69.t Petermann's Stittfteilungen, January, 1878.1Recherches sur le maximum de densile des dissolutions aqueuses."