ers by the author "On Vortex Motion." _Trans_. R.S.E.
April, 1867, and "Vortex Statics," _Proc_. R.S.E. December, 1875; also a
paper by J.J. Thomson, B.A., "On the Vibrations of a Vortex Ring," _Trans_.
R.S. December, 1881, and his valuable book on "Vortex Motion."]

As a step toward kinetic theory of matter, it is certainly most interesting
to remark that in the quasi-elasticity, elasticity looking like that of an
India-rubber band, which we see in a vibrating smoke-ring launched from an
elliptic aperture, or in two smoke-rings which were circular, but which
have become deformed from circularity by mutual collision, we have in
reality a virtual elasticity in matter devoid of elasticity, and even
devoid of rigidity, the virtual elasticity being due to motion, and
generated by the generation of motion.

* * * * *

APPLICATION OF ELECTRICITY TO TRAMWAYS.

By M. HOLROYD SMITH.

Last year, when I had the pleasure of reading a paper before you on my new
system of electric tramways, I ventured to express the hope that before
twelve months had passed, "to be able to report progress," and I am happy
to say that notwithstanding the wearisome delay and time lost in fruitless
negotiations, and the hundred and one difficulties within and without that
have beset me, I am able to appear before you again and tell you of
advance.

[Illustration: FIG. 1]

Practical men know well that there is a wide difference between a model and
a full sized machine; and when I decided to construct a full sized tramcar
and lay out a full sized track, I found it necessary to make many
alterations of detail, my chief difficulty being so to design my work as to
facilitate construction and allow of compensation for that inaccuracy of
workmanship which I have come to regard as inevitable.

In order to satisfy the directors of a tramway company of the practical
nature of my system before disturbing their lines, I have laid, in a field
near the works of Messrs. Smith, Baker & Co., Manchester, a track 110 yards
long, 4 ft. 81/2 in. gauge, and I have constructed a full sized street
tramcar to run thereon. My negotiations being with a company in a town
where there are no steep gradients, and where the coefficient of friction
of ordinary wheels would be sufficient for all tractive purposes, I thought
it better to avoid the complication involved in employing a large central
wheel with a broad surface specially designe