File:Thalassa; an essay on the depth, temperature, and currents of the ocean (1877) (14598394697).jpg

Identifier: thalassaessayond00wild (find matches)
Title: Thalassa; an essay on the depth, temperature, and currents of the ocean
Year: 1877 (1870s)
Authors: Wild, John James
Subjects: Ocean
Publisher: London, M. Ward & Co.
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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tely stretching across theEquator from one hemisphere into the other, intersect theparallel belts of calms and of currents at right angles. Wehave here carried out on a large scale one of those simple ex-pedients by which Nature, in strict obedience to her laws, createsthat endless variety of contrasting phenomena, which the philo-sopher, the poet, the artist, never cease to behold with wonder,and which, while it is the source of all beauty, is, at the sametime, a necessary condition to the existence of all life. Theresult, in the present case, is the creation of numerous areas ofatmospheric and oceanic circulation corresponding with thedifferent areas of land and of water distributed on each sideof the Equator, and the subdivision of the belts of calms intodistinct areas of calms, of which we find one in each of theoceanic basins, in the North and South Atlantic, in .the Northand South Pacific, and in the Indian Ocean. (Plate 4 A.) A comparison of these areas of calms with a chart of
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Oceanic and Atmospheric Currents. 53 isobars shows that they form at the same time areas of highbarometric pressure round which the atmospheric currentsrevolve—with the hands of the watch in the northern hemi-sphere, against the hands of the watch in the southern hemi-sphere, while the equatorial belt and the circumpolar regionsform areas of low barometric pressure. If we now compare achart of isobars and a wind chart with a chart of oceanic surface-currents, we find that there is a remarkable agreement betweenthem. These currents are observed to revolve together withthe winds round the areas of calms and of high barometricpressure placed near the centre of each oceanic basin, about theparallel of lat. 300. The conclusion at which we arrive, that thewinds are the cause of the surface-currents, seems obvious,although we must not forget that even in the absence of wind,the thermal circulation of the ocean would resolve itself into asystem of surface and under-currents. It may be more

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