ccumulators and dynamo-electric machines.

[Illustration: NEW STEAMER PROPELLED BY HYDRAULIC REACTION.]

We now arrive at Messrs. Maginot & Pinette's system, the description of
which will be greatly facilitated by the diagram that accompanies this
article. The inventors have employed a boat 14 meters in length by 1.8
m. in width, and 65 centimeters draught behind and 32 in front. The
section of the midship beam is 70 square decimeters, and that of the
exhaust port is 4. At a speed of 2.2 meters per second the tractive
stress, K, is from 10 to 11 kilogrammes. At a speed of 13.5 kilometers
per hour, or 3.75 meters per second, the engine develops a power of 12
horses. The piston is 19 centimeters in diameter, and has a stroke of 15
centimeters. The shaft, in common, of the pump and engine makes 410
revolutions per minute. It will be seen from the figure that suction
occurs at the lower part of the hull, at A, and that the water is forced
out at B, to impel the vessel forward. C and C' are the tubes for
putting the vessel about, and DD' the tubes for causing her to run
backward. Owing to the tubes, C, C', the rudder has but small dimensions
and is only used for _directing_ the boat. The vessel may be turned
about _in situ_ by opening one of the receiving tubes, according to the
side toward which it is desired to turn.

This boat is as yet only in an experimental state, and the first trials
of her that have recently been made upon the Saone have shown the
necessity of certain modifications that the inventors are now at work
upon.--_La Nature_.

* * * * *

A NEW FORM OF FLEXIBLE BAND DYNAMOMETER.

[Footnote: Read before Section G of British Association.]

By Professor W.C. UNWIN.

[Illustration: Fig. 1.]

In the ordinary strap dynamometer a flexible band, sometimes carrying
segments of wood blocks, is hung over a pulley rotated by the motor, the
power of which is to be measured. If the pulley turns with left-handed
rotation, the friction would carry the strap toward the left, unless the
weight, Q, were greater than P. If the belt does not slip in either
direction when the pulley rotates under it, then Q-P exactly measures
the friction on the surface of the pulley; and V being the surface
velocity of the pulley (Q-P)V, is exactly the work consumed by the
dynamometer. But the work consumed in friction can be expressed in
another way. Putting [theta] for the arc embraced by the be