In many cities the telegraph company has special wires running to various jewelry and other stores and these subscribers get the correct time direct by telegraph from the Naval Observatory for their sounders are connected in the regular line circuit.
The Time Ball.—The Bureau of Navigation got up what is known as the time ball for the benefit of sailing masters in particular and the townsfolk in general.
Fig. 168.—The Time Ball.
In New York and other cities along the seacoasts and lake ports a great ball, weighing in the neighborhood of 100 pounds, having a diameter of over 3 feet and with a hole in its center, is slipped over a pole or flagstaff some 20 feet in height, which is mounted atop of some high building where it can be seen to the best advantage.
The ball is held in position at the top of the pole by an electro-mechanical trigger, which is placed directly in the electric telegraph circuit that runs into the Naval Observatory at Washington. When the time signals are being sent out from the observatory and the telegraph key is closed at exactly noon the trigger which holds the ball in place is released by the current and the ball drops. [Fig. 168] shows a time ball atop of the old Western Union Building in New York.
Fig. 169.—Receiving Time Signals by Wireless.
How Time is Sent by Wireless.—At Arlington, Va., just across the Potomac River from Washington, is one of the most powerful wireless stations in the world, having a sending range of at least 3,000 miles.
Every day at noon time signals like those sent over the wires on land are sent out so that every navigation officer and sailing master whose ships are fitted with wireless apparatus can get the correct time.