THE PRECIPITATION OF CALCIUM CARBONATE IN THE SEA. 485 



greatly commended, as it can be covered over with hatches when not 

 in use, and so affords great economy of deck space, and also has the 

 advantage of bringing the weight of the winch nearer the water-line, 

 and avoiding the unstability that may be caused when a heavy winch 

 is fixed on deck. 



The sounding wire was 2-2 mm. in diameter, and consisted of four 

 strands of eight wires each, made of high tensile steel ; the breaking 

 strain was given at 400 lbs., but in practice I have no hesitation in 

 saying that it far exceeded this figure. The wire was very difficult 

 to kink, and did not show any tendency to untwist or permanently 

 stretch under a tension of about 350 lbs.; it proved in ev^ery way 

 satisfactory, and was supplied by Messrs. Bullivant and Co., of London. 



For measuring the length of wire run out, one of the fathom 

 measuring sheaves as made by the Telegraph Construction and 

 Maintenance Co., of London, was used. This consisted of a sheave 

 containing a steel wheel about 12 inches in diameter, grooved for 

 and made especially to fit the wire ; the length of wire run out is 

 measured by the number of turns of the wheel indicated by a dial on 

 the side of the sheave. The dial has two hands showing fathoms and 

 hundreds of fathoms, the hands revolve backwards on winding in the 

 wire, and so again register zero when the sounding is completed. The 

 axle of the wheel revolves on simple bearings, so the slight inaccuracy 

 unavoidable if ball bearings are employed is prevented. 



Samples of the bottom were obtained with one of the " snapper 

 rods," disengaging a 30-lb. iron weight on touching the bottom, also 

 supplied by the Telegraph Construction and Maintenance Co. This 

 ^3onsisted of two brass jaws closed by a strong spring, and kept apart 

 by a trigger ; on touching bottom the trigger was released and the 

 jaws closed on a sample of the bottom ; at the same time the 30-lb. 

 weight, which was only held in position by the tension of its own 

 weight, was disengaged as soon as the tension was relieved on touching 

 bottom, and so was left behind as the wire was reeled in. 



In order to tell the depth at which bottom was sounded, the wire 

 was led through a pulley connected with a spring balance, which thus 

 registered the tension of the wire. On touching the bottom the decrease 

 in tension, due to the release of the weight, was shown on the dial 

 of the balance. This arrangement was not satisfactory in rough 

 weather, as the rolling of the yacht caused such varying tensions on 

 the wire that it was not always possible to tell the exact depth at 

 which the weight was disengaged. 



For obtaining samples of water for bacterial analysis a special water- 

 bottle was designed for me by Mr. D. J. Matthews. This apparatus is 



