i68 DISCOVERY REPORTS 



though we have since seen it stated that if tallow becomes rancid, free organic acids 

 are developed which have a detrimental effect on wire ropes. 



For determining strains a Salter Dynamometer, reading to a maximum of 6 tons, 

 was used in conjunction with the nipper referred to on p. 207. With this apparatus it 

 is, of course, only possible to read the dead weight or towing strain. With series of 

 water bottles and with any open plankton nets the hauling strain is the greater, and this 

 could only be registered by an instrument similar to the "tensimeter" sometimes used 

 in aeronautical work. 



The following examples of the strains recorded with the dynamometer may be given : 



(i) With a 28 lb. sinker, three reversing water bottles and 3000 m. of 4 mm. wire: 



dead weight 2f cwt. 

 (ii) With a 100 lb. sinker, one 4I m. tow-net and 1800 m. of if in. wire rope, 



speed 2 knots: towing strain 22 to 27 cwt. 

 (iii) With a 100 lb. sinker, two Petersen young-fish trawls attached to 2 m. frames 



and 5000 m. of tapered warp, speed 2 knots: towing strain 41 cwt. 

 (iv) With a 40 ft. otter trawl working at depths of 250 to 350 m., with 800 to 1000 m. 



of if in. wire rope, speed 2-3 knots: average towing strain 18 to 24 cwt., rising 



occasionally on heavy ground to 31 cwt. 



The Sounding Machine, of the well-known Lucas type, is placed on the port side of 

 the forecastle head abreast of the hydrological machine (Plate XIII, fig. i). The machine 

 with its engine is mounted on a bedplate, fitted on a pedestal elevated above the deck, 

 and so arranged that when not in use the whole machine can be brought inboard by 

 means of screw gear fitted under the pedestal. The iron framework seen in the figure 

 is for the support of a canvas cover. The drum of the sounding machine is 144 in. 

 in extreme diameter, the hub 8i in. in diameter, and the width 5^ in. The drum carries 

 5000 fathoms of single-strand piano wire. 



The machine is driven by a Brotherhood 3 cylinder reversing engine, with cylinders 

 set radially at equal angles of 120 degrees, all working on a common crankpin on the 

 well-known Brotherhood principle. The cylinders are of 4 in. diameter and zh in. 

 stroke, and the drive from the engine to the sounding drum is by means of machine- 

 cut gearing, the ratio of the gears being 2-4 to i. 



In bad weather the 'Discovery' rolled heavily and in a strong wind she drifted fast 

 to leeward. In such circumstances sounding often proved a matter of great difficulty, 

 and on a number of occasions the wire parted and the sounding tube was lost. These 

 difficulties, however, were due to the conditions, the machine as a whole proving very 

 satisfactory. One defect was the absence of a clutch. The gear wheel was secured to 

 the shaft carrying the sounding drum by means of a set screw, which was removed at 

 the beginning of sounding operations to allow free motion to the drum and inserted 

 when bottom was reached. The engine was a little fierce in starting, and though it 

 was always run free before hauling began, the delay occasioned by the adjustment of 

 the set screw often prevented an easy start and the sudden jerk sometimes caused the 



