Page:Polar Exploration - Bruce - 1911.djvu/187

Rh so that the expedition was prepared to take up the study of it on the way home. This was done very thoroughly on a line from the mouth of the River Plate along the parallel of 35° to the meridian of Ascension. The depth of water varied from 1,900 to 2,900 fathoms, and the distribution of temperature in the water was, roughly, a warm surface layer of perhaps 100 to 200 fathoms, then a thick layer of water of temperature about 36° F. down to 1,600 fathoms near the coast, and to 2,200 fathoms or thereabouts at sea. Here was a steep temperature gradient falling away rapidly from 35° to 33° F. and more slowly to 32.5° F. The occurrence of the steep gradient shows a renewal of the water and therefore a current. The observations of the Valdivia show a similar distribution in latitude 60° to 63° S., with this difference—that the surface layer is colder than the intermediate, being about 34° F. The bottom layer has as low a temperature as 31.5° F." Unfortunately at that time there were not enough determinations of temperature of the deeper layers to indicate the gradient which separate the cold bottom water from the comparatively warm intermediate water, but now the additional observations taken on board the Scotia, Gauss and Antarctic should help to fill up the gap. The results of the extensive observations by these three expeditions will be