Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/77

 Pouillet * briefly discusses ocean temperatures, and concludes that, although all the difficulties of the case are not solved, it seems certain that there is generally an upper current carrying the warm tropical waters towards the polar seas, and an undercurrent carrying the cold waters of the arctic regions from the poles to the equator.

The early evidence on the subject was necessarily contradictory, as the instruments were often imperfect, and the temperature in the early experiments was often taken by means of water or mud brought to the surface. Off the coast of Greenland, Scoresby always found the temperature in descending to increase, in some cases, to 36° or 38° F., while the surface-temperature was only from 28° to 30°. He mentions, however, that in lat. 72° 7' N., long. 19° 11' W., where the temperature was 34° F. at the surface, it was 29° at a depth of 700 feet. Sir Edward Parry found the surface-temperature off Spitzbergen to vary from 28° to 31°, and at depths of from 400 to 600 feet to be from 30° to 28°. Sir John Boss found the temperature at a depth of 2520 feet in Melville Bay to be 29-1/2° ; in Lancaster Sound, depth 7900 feet, 29° ; and in lat. 72° 33' N". and long. 73° 7' W. the surface-temperature was found to be 35°, decreasing gradually to 28-3/4° at a depth of 6000 feet. More lately the carefully made observations of M. Chas. Martins in the Spitzbergen seas led him to the following conclusions : —

1st. In the months of July and August the temperature of the surface, although near freezing-point, is always somewhat above it.

2nd. From the surface to a depth of 240 feet, the temperature here increases, there decreases.

3rd. From 240 feet to the bottom the temperature always decreases.

4th. The mean temperature of the water at the bottom of the sea is 28-84° F. (- 1.75° C).

The greatest depths of the soundings seem to have been from 2000 to 2800 feet.

These low deep-sea temperatures have not only been found to prevail in high northern latitudes, but to extend, though in some- what diminished force, to the equator, and thence to the Antarctic regions.


 * Elem. de Phys. vol. ii. p. 667, 1847.