. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography deeoending, oarsmen manoeuvred the small boat to com- pensate for currents and windage. Thus the sounding line was kept vertical so that line angle errors were minimized'-'. Ross identified the bottom by a decrease in the rate of pay out of line from the free-spooling reel. The velocity of descent was ascertained by noting the time between successive increments (100 fathoms) which had previously been marked on the 3,600 fathom line. An abrupt decrea
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography deeoending, oarsmen manoeuvred the small boat to com- pensate for currents and windage. Thus the sounding line was kept vertical so that line angle errors were minimized'-'. Ross identified the bottom by a decrease in the rate of pay out of line from the free-spooling reel. The velocity of descent was ascertained by noting the time between successive increments (100 fathoms) which had previously been marked on the 3,600 fathom line. An abrupt decrease in the rate of pay-out was indicative of bottom contact. This method was necessary because it is not feasible to "feel" bottom at abj^ssal depths. Maury*, who later formalized the rate-of-pay-out technique in his law of plummets descent, was aware that deep undercurrents could induce "swigging forces upon the bight" which could cause a line to run out for ever or, because sounding lines are of finite length, until the end spooled off and disappeared beneath the surface. Thus one could merely have measured the length of a piece of line rather than have determined the depth of the ocean. We suppose that this is a calligraphic error in transcrip- tion, for a poorly handwritten "5" may appear to be a "6". There is certainly no justification for unrounding Ross's soimding because of the many inaccuracies involved in obtaining it. Similarly, the error in sounding location must have resulted from a creeping error in drafting without reference to the original source. Because literally millions of soundings are now taken each year, it seemed appropriate to us to ask the U8C and GSS Discoverer, while en route to Tristan da Cunha, to survey Ross's site as a commemorative gesture. The site is located about 600 miles NNW of Tristan and approximately half-way between the lower halves of South America and Africa. On January 23, 1968, a brief survey w
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