Читать книгу Mechanics: The Science of Machinery - A. Russell Bond - Страница 27

Table of Contents

While we may well marvel at the precision of the chronometer, it is equally marvelous, if not more so, that we may equip ourselves for a few dollars with a timepiece which is so wonderfully accurate as to vary little more than a second per day. If one took the pains to regulate his watch carefully, any of the better makes could be adjusted to such accuracy.

There is nothing very mysterious about the mechanism of a watch. It consists merely of a train of gears which slow down the motions of the mainspring to a convenient speed; and these gears moreover keep the proper relation between the hour and minute and second hands. But when we reflect that a small watch possesses a tiny second hand which travels something like ten miles in a year, and that if carefully regulated it will not vary from that of another watch in the whole journey by more than six or eight inches at the most, we certainly have a reason to marvel. There are 86,400 seconds in a day, and a watch is usually arranged to make five beats per second or 432,000 per day. The interval between beats must be adjusted with such minuteness that one beat must not differ from another by 1/86000 part of a second, else the watch will register more than a second fast or slow at the end of a day. And yet watches capable of such precision are being turned out daily by the thousands. Of course, such perfection would be absolutely impossible without the use of extremely accurate machine tools. It would have been impossible as long as we had to depend upon a watchmaker to make a watch by hand.