Scientific American Supplement, No. 717, September 28, 1889 | Page 9

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.
It will thus be seen that model experiments had been made by
investigators long before the time of the late Dr. William Froude, of
Torquay. It was not, however, until this gentleman took the subject of
resistance of vessels in hand that designers were enabled to render the
results from model trials accurately applicable to vessels of full size.
This was principally due to his enunciation and verification by
experiment of what is now known as the "law of comparison," or the
law by which one is enabled to refer accurately the resistance of a
model to one of larger size, or to that of a full sized vessel. In effect, the
law is this--for vessels of the same proportional dimensions, or, as
designers say, of the same lines, there are speeds appropriate to these
vessels, which vary as the square roots of the ratio of their dimensions,
and at these appropriate speeds the resistances will vary as the cubes of
these dimensions. The fundament upon which the law is based has
recently been shown to have found expression in the works of F. Reech,
a distinguished French scientist who wrote early in the century. There
are no valid grounds for supposing that the discovery of Reech was
familiar to Froude; but even were this so, it is abundantly evident that,
although never claimed by himself, there are the best of grounds for
claiming the law of comparison, as now established, to be an
independent discovery of Froude's.
Dr. Froude began his investigations with ships' models at the
experimental tank at Torquay about 1872, carrying it on
uninterruptedly until his death in 1879. Since his decease, the work of
investigation has been carried on by his son, Mr. R. E. Froude, who
ably assisted his father, and originated much of the existing apparatus.
At the beginning of 1886, the whole experimental appliances and
effects were removed from Torquay to Haslar, near Portsmouth, where
a large tank and more commodious offices have been constructed, with
a view to entering more extensively upon the work of experimental
investigation. The dimensions of the old tank were 280 ft. in length, 36

ft. in width, and 10 ft. in depth. The new one is about 400 ft. long, 20 ft.
wide, and 9 ft. deep. The new establishment is more commodious and
better equipped than the old, and although the experiments are taken
over a greater length, the operators are enabled to turn out results with
as great dispatch