Page:Polar Exploration - Bruce - 1911.djvu/186

182 common feature of Antarctic water found by all expeditions," says Mr. J. Y. Buchanan, "is the thick warm layer lying between a cold layer at the surface and another cold layer at the bottom."

The intermediate warm layer in glacial seas was found by the Challenger in her Antarctic cruise. Although she was furnished only with the "Millar-Casella" thermometer, a protected maximum and minimum thermometer of the Six type, by the skilful handling of this instrument her staff was able to make a perfect thermometrical survey of the water from the surface to the depth where the maximum temperature of the first warm layer was found, which was at 200 fathoms, and to fix the superior and inferior limits to the temperature of all the water below (Challenger Report-Narrative, vol. i, Part I, p. 419).

Buchanan points out that, "One of the striking features of the ocean discovered by the Challenger expedition was the extensive area of very cold water which occupies the bottom of the sea from the east coast of South America to the ridge which runs north and south in the meridian of the island of Ascension. Here the bottom temperature was found to be 32.5° F. The existence of this exceptionally cold bottom water was discovered on the outward voyage in soundings near the Brazilian coast,