Note 21 — Chapter IV · PROGRESS IN THE SCIENCE OF SHIPBUILDING.

With the view of effecting an economy in time, and to enable the trials at progressive speeds to be carried out while vessels are in a lengthened run out to sea, a method has been proposed by Mr J. H. Biles, naval architect to Messrs J. & G. Thomson, and adopted on board the vessels tried by that firm, and also experimented with on some of the vessels turned out by Messrs W. Denny & Bros., by which the necessity for running with and against the tide on the measured mile is entirely obviated. The principle of the method is to measure the time that a certain part of the length of the ship takes to pass an object thrown from the bows of the vessel well clear of the side. For full particulars, both of the apparatus employed and of the results of actual trials by this method compared with trials made on the measured mile, see paper on “Progressive Speed Trials,” by Mr Biles, in the Transactions: Institution of Naval Architects, vol. xxiii., 1882.