y supports.

The girders were, in fact, resting upon rollers, and the roller apparatus
themselves were renting upon wedges, and there was no anchorage to prevent
a transverse sliding.

Under the prolonged thrust of a very high wind, the superstructure, by
reason of its considerable projection, must have begun to swing like a
pendulum. These oscillations acquired sufficient amplitude to cause the
superstructure to gradually move upon its rollers until the latter no
longer bore beneath the webs. The flanges therefore finally bent upward
where they rested upon the rollers, through the action of the weight which
they had to support, and the entire superstructure slid off into space.

An examination of the bent pieces seems to give great value to this
hypothesis.--_Le Genie Civil_.

* * * * *

JOY'S REVERSING AND EXPANSION VALVE GEAR.

[Footnote: A paper read before the Mechanical Section of the British
Association, at Montreal, August, 1884.]

Four years ago, in August, 1880, a paper was read on this subject before
the Annual Summer Meeting of the Mechanical Engineers' Society of Great
Britain, then held in Barrow-in-Furness, describing this valve motion and
its functions, which was then comparatively new. It was, however,
illustrated by its application to a large express goods (freight) engine,
built by the London and North-Western Railway Company (England) specially
to test the advantages and the endurance of the gear. This engine had
cylinders of 18 inches in diameter and 24 inch stroke, and six wheels
coupled 5 feet 1 inch diameter, and was designed by Mr. Webb, the
Company's chief engineer, for their heavy fast goods traffic on the main
line. The engine has been running this class of traffic ever since. In
January, 1884, it was passed through the repair shops for a general
overhauling, when it was found that the valve motion was in such good
condition as to be put back on the engine without any repairs.

The main object of this present paper is to deal with the advantages of
the valve gear and its application to various classes of engines both on
land and at sea, and with the results of such applications, rather than
treating it as a novelty, to give an exhaustive description of its
construction and functions, which was done in the paper above referred to.
A very short description of its action and main features will, however,
be necessary to the completeness of the paper,