“Circulation is responsible for the aeration of The Deeps, without which all but the uppermost stratum would be a waste more desert than the Sahara” —H. B. Bigelow INTRODUCTION In the early investigations of marine biology, many scientists believed that the deeper parts of the ocean must be anaerobic and azoic. However, deeper and deeper probes in the latter half of the nineteenth century showed that life existed and that dissolved oxygen was present to the greatest depths sounded (C. W. Thompson, 1874). As early as 1869, the oxygen content at depths as great as 2090 fathoms had been determined by W. L. Carpenter (1874), the chemist aboard the Porcupine; he ventured to predict to the biologists whether their dredge hauls would be “good” or “bad”, depending on the proportions of dissolved oxygen and carbon dioxide he found in the water. Dittmar’s analyses of oxygen samples taken on the Challenger expedition in 1873–1876 (Dittmar, 1884) were the first relating to the general distribution in the world oceans. Dittmar was surprised to find surface-oxygen contents showing “negative deficits” from the amounts he computed for saturation, and he noted “very small values for the dissolved oxygen. . . at many places of the ocean bottom [and] . . . occasionally even at moderate depths. . . .” (p. 226). He also observed (p. 225) “Amongst the many deep-sea waters which were analysed for their gas contents, we found none that were quite free from absorbed oxygen, which confirms our conviction that...