e open air.

The admission of air to the smaller cylinder is regulated by an
adjustable cut-off apparatus, which admits of maintaining a uniform
power under a variable pressure. When the reservoir at first starting
contains air at a very high pressure, the cut-off is adjusted so that
the small cylinder receives a very small charge of air at each stroke;
when the pressure in the reservoir diminishes the cut-off is delayed so
that a larger quantity of air is admitted to the small cylinder; and
when the pressure in the reservoir is so far reduced that the pressure
on the smaller piston gives very little power, the supply passages are
kept open so that the air acts directly on the piston of the larger
cylinder. This arrangement is also available when the air pressure is
high and great power is required for a short time, as, for example, in
starting a locomotive.

It is, perhaps, needless to mention the advantages a motor of this kind
possesses over the steam locomotive. The absence of smoke and noise
renders it particularly desirable for tunnels, elevated roads, and, in
fact, for any city railroad.

Further information in regard to this important invention may be
obtained by addressing Mr. R. Ten Broeck, at the Windsor Hotel, New
York.

* * * * *

TELEGRAPH WIRES UNDERGROUND.

Philadelphia newspapers report that the American Union Telegraph
Company are about to try in that city the experiment of putting their
wires underground. The plan works well enough in European cities, and
there would seem to be no reason why it should not succeed here, save
the indisposition of the companies to bear the first cost of making the
change. For some months the Western Union Telegraph Company has had the
matter under consideration, but will probably wait until pressed by a
rival company before it undertakes the more serious task of taking down
its forest of poles and sinking the wires which contribute so much to
the prevailing ugliness of our streets. Sooner or later the poles and
wires must come down; and it is altogether probable that the change will
be beneficial to the companies in the long run, owing to the smaller
cost of maintaining a subterranean system. It will certainly be an
advantage to the community.

* * * * *

IMPROVED SAFETY NUT.

That a safety nut so simple and so obviously efficient as the one shown
in the annexed engraving should be