PLATE XXX 



Fig. I. Passage from open water through brash ice and loose pack, off 



the ice barrier in Long. i° E. Sea, calm; wind, force 2. Speed of 



ship, 9 knots. Vertical scale, x 972. In loose pack the echo, even 



at this shallow depth, is almost obliterated by the noises set up by 



the scraping of ice across the face of the hydrophone. This record 



shows part of the sea floor which is relatively free from irregularities. 



Position (at 1030 hr.) 69° 50-2 'S, 00' 567' E. (Part of Record 



VII/39.) See Text-fig. 2 (a), p. 45- 



Fig. 2. Re-echoes at 1780-2000 fm. (3255-3658 m.) from soundings 



between 890 and 1000 fm. (1628 and 1829 m.) during the survey 



of Clarence Island. Speed of ship, ca. 4-5 knots. Vertical scale, 



xc«. 4-9. (Part of Record XXVIII/37.) See Text-fig. 3(c), p. 46- 



Fig. 3. Section of record showing the effect of a rising wind and sea on 



the echo, at a depth of approximately 270 fm. (494 m.), on the 



Discovery Bank. Section begins with recording at a speed of ship 



of 2 knots, which increases to 8-5 knots at the point indicated. 



Wind was NW, 22-27 knots and sea, NW, force 5 ; there was also 



a moderate North-westerly swell. Ship's course, W. Weather was 



deteriorating rapidly. Vertical scales : at 2 knots, x 2- 16 ; at 8-5 knots, 



x9-i8. From 42° 03-9' S, 00° 03-5' E to 42° 04-1' S, oo°ii'E. 



(Part of Record XXVI/38.) See Text-fig. 2 {a), p. 45. 



Fig. 4. Simple 'crossover' at a depth of 215 fm. (393 m.). Speed of 



ship, 9-5 knots. Vertical scale, x 10-26. Position, approx., 14 miles 



N 63° W of C. Finisterre. 



