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