TRANSACTIONS OF SECTION A. 629 



7. Recent Improvement in Apparatus and Methods for Sounding Ocean 

 Depths. By Rear-Admiral Daniel Ammen, U.S. Navy. 



The author, after briefly noticing the advances made by Berryman, Brooke, 

 Sands and others, in deep-sea sounding apparatus, proceeds to the soundings, by 

 Sir W. Thomson, in the Bay of Biscay in le72, at a depth of 2,700 fathoms. He 

 used pianoforte wire, Birmingham gauge 22, weighing 14| lbs. to the nautical 

 mile, capable of bearing a strain of 230 lbs. His dynamometer, had three miles 

 in length of this wire been wound upon the drum, would have been still so 

 portable that one man could have carried it with ease. 



Early in 1873 the Navy Department was preparing to make extended soundings 

 in the Pacific Ocean. The Chief of Bureau of navigation, charged with the 

 execution of this work, asked the advice and assistance of Sir William Thomson. 

 He was good enough to order wire and such apparatus as his personal experience 

 suggested, and to send carefully prepared instructions for effecting the object in 

 view ; in short, he did everything within his power to make the use of his 

 apparatus successful. The substitution of it and its effective manipulation by 

 Captain Belknap, U.S.N., marked an era of progress in deep sounding and in 

 possibilities of obtaining true ocean depths, as truly as did the steamship mark an 

 advance in traversing wide and stormy seas with celerity and certainty. At that 

 time Belknap commanded the ' Tuscarora,' and until the sounding apparatus was 

 sent, had only the fittings that belong to vessels of war. Notwithstanding these 

 disadvantages, the results obtained were eminently satisfactory. For specific 

 information reference may be made to No. 51 of the Hydrographic Office publica- 

 tions, entitled ' Deep-sea Soundings in the North Pacific Ocean,' 1874. 



In depths of 2,500 fathoms Belknap found it necessary to make several 

 additional revolutions of the drum by hand, on the sinker striking the bottom, to 

 prevent jerks and strains on the wire which otherwise would have occurred from 

 the rolling of the ship. This necessity was due to the almost instantaneous ceasing 

 of the drum to revolve on the sinker touching the bottom. He reported his 

 soundings at this depth as probably more accurate than many casts in depths of 

 100 fathoms with an ordinary lead and line. He added : ' I expect to accomplish 

 all the work with it (Sir William Thomson's apparatus) which the Department has 

 assigned me, and if I succeed, no greater compliment could be paid to the genius 

 of the inventor.' 



The winding up of miles of wire on a light drum gave a cumulative pressure on 

 the original apparatus in deep soundings, such as to make a continuous system of 

 repair necessary, and finally the substitution of steel drums in the Naval service. 



To fully appreciate the advance made through the use of this apparatus, it is 

 necessary to bear in mind the tons of rope required to reach depths of four or five 

 miles, and its rapid deterioration from use, the cumbrous apparatus, the slowness 

 of the process even under the most favourable conditions, and what is of greater 

 import, the uncertainty as to the actual depth sounded, arising in part from the 

 under-currents of the ocean carrying great bights of rope in one or more directions, 

 and in part from the very small proportion the weight of the sinker must bear 

 to the hemp line, but in a more marked degree from the ' stretch ' of the rope 

 under tension, and the gradual shortening of it as soon as the sinker reached the 

 bottom. 



The report of the Secretary of the Navy for 1874, p. 61 , discusses the advantages 

 gained by the use of wire as follows : the small amount of weight and space 

 required for the apparatus; the large weight of the sinker relatively with the 

 weight of the wire necessary, even in sounding the greatest depths, and the very 

 little surface friction of wire in its descent. Miles of wire have very little ' stretch ' 

 at ordinary tension, and hemp line a great deal, from which in the first case the 

 indications of the dynamometer would be almost instantaneous, and in the second 

 would be obscure and quite uncertain as to the exact depth and moment when the 

 sinker reached the bottom. Other advantages are : the ease with which the wire 

 is preserved from deterioration. It stated further : ' The problem of measuring 



