to the
square inch. The effect, however, of the percussion might add considerably
to this, though the latter would be confined in effect to a single
instance. In regard to the practical result from this arrangement, which
was continued in operation for several years, it was found not to obviate
the necessity of producing sounds of greater power. It is, however,
founded on an ingenious idea, and may be susceptible of application in
other cases."

There is now a first-class siren in duplicate at this place.

The sixty-six steam fog-signals in the waters of the United States have
been established at a cost of more than $500,000, and are maintained at a
yearly expense of about $100,000. The erection of each of these signals
was authorized by Congress in an act making special appropriations for its
establishment, and Congress was in each instance moved thereto by the
pressure of public opinion, applied usually through the member of Congress
representing the particular district in which the signal was to be
located. And this pressure was occasioned by the fact that mariners have
come to believe that they could be guided by sound as certainly as by
sight. The custom of the mariner in coming to this coast from beyond the
seas is to run his ship so that on arrival, if after dark, he shall see
the proper coast-light in fair weather, and, if in thick weather, that he
shall hear fog-signal, and, taking that as a point of departure, to feel
his way from the coast-light to the harbor-light, or from the fog-signal
on the coast to the fog-signal in the harbor, and thence to his anchorage
or his wharf. And the custom of the coaster or the sound-steamer is
somewhat similar.

* * * * *

TREVITHICK'S ENGINE AT CREWE.

The old high-pressure engine of Richard Trevithick, which, thanks to Mr.
Webb, has been rescued from a scrap heap in South Wales, and re-erected at
the Crewe Works. We give engravings of this engine, which have been
prepared from photographs kindly furnished to us by Mr. Webb, and which
will clearly show its design.

[Illustration: TREVITHICK'S HIGH PRESSURE ENGINE AT CREWE.]

The boiler bears a name-plate with the words "No. 14, Hazeldine and Co.,
Bridgnorth," and it is evidently one of the patterns which Trevithick was
having made by Hazeldine and Co., about the year 1804. The shell of the
boiler is of cast iron, and the cylinder, which is vertical, is cast in
one with it, the