Page:Popular Science Monthly Volume 11.djvu/190

178 could be remedied by a board of inspection appointed by the insurance companies, which should refuse to insure the cargo or hull of any seagoing ship unless her chronometers were found, after trial, to be satisfactory. Part of the error is undoubtedly due to the bad navigation of the captain, who, in distant ports not provided with time from an astronomical observatory, determined the error of his chronometer himself, and that not always correctly. But the great source of error was the fact that the rate of the chronometer assigned at the port of sailing did not serve throughout the voyage.

It will be then of some interest to describe the measures now taking in the United States to provide the sea-going ships sailing from our various ports with an accurate standard time; and, further, to explain the facilities offered by the United States Naval Observatory to railways, manufactories, and others, in the providing of a time by which to regulate their affairs.

The Superintendent of the Naval Observatory, the late Rear-Admiral C. H. Davis, some time ago proposed to the authorities of the Western Union Telegraph Company the erection of a large time-ball upon their new building on Broadway, near the City Hall. This time-ball it was proposed to drop daily by telegraph at New York noon. It is to be dropped exactly at 11h 47m 49.53s of Washington local time, which is New York noon, 12 0h 0.00m or 4h 56m 1.65s of Greenwich time. It will thus be available both for the citizens, railways, etc., of New York, and for the ships sailing from port It is to be mounted upon the large iron flagstaff on top of the east tower of the Western Union building, the base of the staff being about 230 feet above the street, and the ball being dropped from a part of the staff about 25 feet above this. The whole expense of the apparatus, which is considerable, and the management of it, which requires the attention of a laborer and of a skilled electrician, have been assumed in a public-spirited manner by the Western Union Telegraph Company, for the benefit of the citizens and the shipping of New York City.

The apparatus employed may be briefly described as follows:

Around the iron mast, which is of great strength, is fastened an iron jacket, sliding up and down freely upon it. On this is fitted a ball three feet six inches in diameter, made of copper-wire netting, and painted black. The interstices of the netting allow of a free passage of the wind through the ball, so that less strain is exerted upon the mast, and a larger ball is permissible than there otherwise would be.

At the bottom of the jacket are a coiled spring and a buffer encircling the mast, which take the considerable blow of the falling ball. At 11h 55m of New York time, the ball is hoisted half-way or more up the mast, and at 11h 58m it is hoisted completely up, and the halliards are attached at 11h 59m to a lever actuated by an electromagnet. At exactly noon an electric signal releases the lever, and the ball falls by its own weight.