"On the apex of this hole he erected a chimney which terminated in a tube surmounted by a locomotive-whistle. By this arrangement a loud sound was produced as often as the wave entered the mouth of the indentation. The penetrating power of the sound from this arrangement would not be great if it depended merely on the hydrostatic pressure of the waves, since this under favorable circumstances would not be more than that of a column of water twenty feet high, giving a pressure of about ten pounds 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.]