In estimating the power required for vessels of unusual types or of abnormal speed, where empirical formulae do not apply, and where data for previous ships are not available, the system of experimenting with models is the only trustworthy expedient.  In the case of the Czar’s extraordinary yacht, the Livadia, already referred to, it may be remembered that previous to the work of construction being proceeded with, experiments were made with a small model of the vessel by the late Dr. Tideman, at the government tank at Amsterdam.  On the strength of the data so obtained, coupled with the results of trials made with a miniature of the actual vessel on Loch Lomond, those responsible for her stipulated speed were satisfied that it could be attained.  The actual results amply justified the reliance placed upon such experiments.

The design of many of her Majesty’s ships has been altered after trials with their models.  This was notably the case in connection with the design of the Medway class of river gunboats.  The Admiralty constructors at first determined to make them 110 ft. long, by only 26 ft. in breadth.  A doubt arising in their minds, the matter was referred to the late Mr. Froude, who had models made of various breadths, with which he experimented.  The results satisfied the Admiralty officers that a substantial gain, rather than a loss, would follow from giving them much greater beam than had been proposed, and this was amply verified in the actual ships.

So long ago as the last decade of last century, an extended series of experiments with variously shaped bodies, ships as well as other shapes, were conducted by Colonel Beaufoy, in Greenland dock, London, under the auspices of a society instituted to improve naval architecture at that time.  Robert Fulton, of America, David Napier, of Glasgow, and other pioneers of the steamship, are related to have carried out systematic model experiments, although of a rude kind in modern eyes, before entering on some of their ventures.  About 1840 Mr. John Scott Russell carried on, on behalf of the British Association, of which he was at that time one of its most distinguished members, an elaborate series of investigations into the form of least resistance in vessels.  For this purpose he leased the Virginia House and grounds, a former residence of Rodger Stewart, a famous Greenock shipowner of the early part of the century, the house being used as offices, while in the grounds an experimental tank was erected.  In it tests were made of the speed and resistance of the various forms which Mr. Russell’s ingenuity evolved—­notably those based on the well-known stream line theory—­as possible types of the steam fleets of the future.  All the data derived from experiment was tabulated, or shown graphically in the form of diagrams, which, doubtless, proved of great interest to the savants of the British Association of that day.  Mr. Russell returned to London in 1844, and the investigations were discontinued.