actuates a revolution counter, and a clock
measures the time employed in the experiment. In order to obtain a
simultaneous starting and stopping point for all these apparatus, they
are connected electrically, and, through the maneuver of a commutator,
are all controlled at once. The electric current is furnished by two
series of bichromate batteries.

The tests of traction machines are effected by means of a
three-wheeled vehicle carrying a dynamometer. The front wheel is
capable of turning freely in the horizontal plane, and the dynamometer
is mounted upon a frame provided with a screw that permits of
regulating its position according to the slope of the ground. The
method of suspension of the dynamometer allows it to take
automatically the inclination of the line of traction without any
torsion of the plates. There are two models of this vehicle, one
designed to be drawn by a man, and the other by a horse.

The station is provided, in addition, with registering pressure
gauges, a large double dynamometric indicator, a counter of
electricity, balances of precision, etc.

An apparatus designed for measuring the rendering of presses is now in
course of construction.

Although the station has been in operation only from the 1st of
January, twenty-five machines have already been presented to be
tested.--_Extract from Le Genie Civil_.

* * * * *

WATER SOFTENING AND PURIFYING APPARATUS.

We have recently had brought under our notice a system of water and
sewage purification which appears to possess several substantial
advantages. Chief among these are simplicity in construction and
operation, economy in first cost and working and efficiency in action.
This system is the invention of Messrs. Slack & Brownlow, of Canning
Works, Upper Medlock Street, Manchester, and the apparatus adopted in
carrying it out is here illustrated. It consists of an iron
cylindrical tank having inside a series of plates arranged in a spiral
direction around a fixed center, and sloping downward at a
considerable angle outward. The water to be purified and softened
flows through the large inlet tube to the bottom, mixing on its way
with the necessary chemicals, and entering the apparatus at the
bottom, rises to the top, passing spirally round the whole
circumference, and depositing on the plates all solids and impurities.

All that is needed in the way of attention, even when dealing with
sewage, or