THE INDEPENDENT CENTRE SECONDS WATCH is peculiarly adapted for the use of the medical profession. By means of its two trains it carries, besides the ordinary hands denoting hours, minutes, and seconds, a long seconds hand which can be stopped without stopping the watch. It is made with a stem winder, and therefore requires no key. THE SPLIT CENTRE SECONDS is not quite so complicated as the last named. It has two centre second hands revolving round the dial, the one directly over the other, as also, in another part of the dial, a small hand revolving five times in a second. Upon pressing a stop-piece one of the long second hands is stopped, and another pressure will stop the other--the space between the two hands will then indicate precisely the time occupied by the event which it is desired to measure. Another push to the stop-piece will make both hands again fly together, and enable the operator it may be to make a new experiment or observation. +----------------------------------------------------------------------+ | [Illustration: The Perpetual Calendar Keyless Watch.] | +----------------------------------------------------------------------+ THE PERPETUAL CALENDAR KEYLESS WATCH, shows on its dial the year, the month of the year, the day of the month, the day of the week, the phases of the moon, as well as hours, minutes, and seconds. It requires no setting, as the old-fashioned Calendar Watch did at certain intervals, but, by a very ingenious contrivance, the changes from month to month, as for example from February 28th to the 1st of March, or from 30th or 31st of other months to the 1st of the next, are all performed by the watch, which also of itself marks the extra day for Leap Year. When to all the above are added, as is sometimes done, the Minute Repeating Work to repeat the hours, quarters, and minutes, it may be said that the power of complication can no farther go within the limits of the small box which is called a watch case,--for these watches are provided with either Lever, Duplex, or Chronometer Escapements as may be preferred, and with compensation balances adjusted to serve in extremes of temperature. But in the examples set forth in the following illustrations, it will be seen that superadded to all the foregoing are a thermometer, and an index showing the calendar by the old and new style, as indicated by the words Gregorian and Russian,--the former referring to Pope Gregory who decreed the alteration to the new style, and the latter to the fact that the Russians still reckon by the old style. +----------------------------------------------------------------------+ | [Illustration: Perpetual Calendar.] | +----------------------------------------------------------------------+