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The Corresponding Secretary then read a paper by Captain Belknap, of the S. S. Tuscarora on Deep Sea Soundings, which was followed by explanations by Captain Belknap himself of the apparatus employed in the soundings; and also of a Diagram exhibiting an outline of the ocean bed from San Diego, in California, to the Sandwich Islands; thence to the Bonin Islands, and thence to Japan. The future line of soundings is to run along by the Aleutian Islands to Alsaka.
The President tendered the thanks of the Society—afterwards confirmed by a special vote—and remarked on the exceptional value and interest of papers such as that just read.
Prof. W. E. Ayrton said:—
Captain Belknap has ably described in his paper the history of deep sea sounding apparatus. As he has said, the methods by which attempts have been made to obtain accurate results may be divided into four classes— the use of a very heavy weight to keep the line approximately vertical, which weight had to be left at the bottom at every sounding so that the mere cost of metal thrown away was, in a long expedition like the present, considerable—next, an apparatus like a patent-log which recorded on a tell-tale arrangement attached to it, its descent in the sea—thirdly, sounding by time, in which case there was attached to the weight only a very light line the object of which was merely to determine when the weight reached the bottom, it having been proved that a body falling unimpeded through water moves through equal spaces in equal times, quite unlike the case of a falling body in air, where if the time is doubled the space is quadrupled; with this latter method of sounding, however, not only the weight but the cord was also lost. All the above methods have proved more or less unsatisfactory in deep seas where there are surface or under-currents. After the paper we have heard from Captain Belknap, bearing valuable testimony as it does to the efficiency of Sir William Thomson's piano-forte wire arrangement, it is with diffidence that I am now going to say a few words regarding that system. Perhaps the fact of my having been present on the occasion when Sir William first brought his method before the notice of public, at the Meeting of the British Association held at Brighton in 1872, now enables me to say something about the line of thought which gave birth to this invention and may plead as an excuse for my apparently trenching on a subject Captain Belknap has made so throughly his own. Owing to that little hesitation naturally displayed by Mr. Syle regarding the infliction on the company of the valuable technical details contained in the paper we have just heard him read, I am afraid that the points of merit of the Thompson apparatus may not have been made clear to some of those present. It was quite evident to Sir William that in order to have accurate deep sea soundings fine wire and not cord must be used; the first point, therefore, was to devise a contrivance by which the paying out wheel should be automatically stopped the moment the weight reached the bottom. This he has succeeded in doing in a very ingenious way. To the end of the
