The next thing he does is to change this absolutely correct star time into mean solar time, when it is ready to be sent all over the United States east of the Rocky Mountains by telegraph. The Pacific Coast folks get their correct time from a Government observatory at Mare Island in San Francisco Bay. =How Time Is Sent by Telegraph.=—The wires of the Western Union Telegraph Company run into the United States Naval Observatory at Washington, and for a few minutes each day all of this company’s wires are controlled by the Government. About five minutes before 12 o’clock noon, standard time at Washington, each day the wires all over the country east of the Rockies are _cleared_ and all business and other messages are cut off for the time signals. At five minutes of 12 sharp the United States Naval Observatory begins to send the beats of every second of the wonderfully accurate observatory clock, which are ticked out on telegraph sounders in all the cities and towns. But no, not every beat, for the 29th second of each minute, the last 5 seconds of each of the first 4 minutes, and then the last 10 seconds of the last minute are not sent. The first click of the sounder after the 10 second rest is the noon signal, and all local clocks are set by it. 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. [Illustration: 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. [Illustration: 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.