This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1880 Excerpt: ...are in separate buildings, but all the comparisons are made by means of a chronograph. This apparatus records by means of a stylographic pen, making a trace upon a revolving cylinder driven by clock-work and controlled by delicate machinery. The swing of the pendulum of the standard clock makes and breaks an electrical current that causes the pen to move aside, and, as a result, the trace of the pen is broken or dented with each swing of the pendulum. The observer at the transit instrument holds in his hand a circuit-closer in electrical connection with the chronograph, and, on observing the passage of a star across the field of his glass, closes the circuit, and the pen makes a dent in its trace. It is easy then to compare the dents on the trace marked by the pendulum and those that record the transit of the star, and the difference between these dents records the difference, in tenths of a second, between the clock and the star. At some distance from the observatory, in the office of a safe deposit company, is a second chronograph, also recording the beats of the standard dock. In the vaults of the company is a set of drawers, designed to be closed air-tight and securely locked, for containing the watches to be examined. Under the drawers is a refrigerator, with the proper water-tight tanks for holding the watches while undergoing the cold test. Next to it is an oven for the hot test. This oven is heated by hot water pipes (heated by gas), and is properly supplied with chemicals for obtaining a perfectly dry air. On the arrival of a watch for testing, it is at once removed, numbered, entered by its maker's name and number in the books, and placed, with the dial uppermost, in a compartment in one of the drawers. If it has run down, it is wound up; but in t...
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