But it was not always convenient for one to keep awake in order to waken his companions. The one who was on guard was as sleepy as any of the rest: so the inventive brains of the Yankee boys were set to work to find some way of giving an alarm at the right time. Let it be remembered that, while primitive alarm-clocks were to be had in Europe, and while "repeating"-watches were a luxury in America, neither of them were to be found in New England as it was then. Even if the repeating-watch had been in general use, it was valueless, except to tell the time in the dark when one was awake. The invention of the alarm-clock was, therefore, a greater advance in the history of clock-making than was the invention of time-locks in the history of lock-making. The essential feature of the time-lock is a chronometer that turns a wheel containing a pin so adjusted that it will reach a certain point in a fixed time. Then a "dog" drops down, removes the obstruction, and allows the bolt to be shoved back. Two chronometers are used, so that, in case one runs down, the other will do the work. They are hung on springs, for fear that they will run down if the burglars should use dynamite, or some other explosive, to give them a sudden jar.
The Yankee boys, at the time that I have spoken of, were equal to the difficulty of awakening at the exact time. They invented a contrivance which was an indication of what was coming in both the alarm-clock and the time-lock. Indeed, it was so nearly a combination of the two that we must take away from the more modern inventors some of the credit and bestow it upon the boys.
In order to explain the plan more clearly, I ought first to say that the watches worn by both the men and the boys were of the large and coarse pattern known as "bull's-eyes"—a name given because the crystals were very thick, and bulged out something like the lens of a dark-lantern. The watches of this kind were not only very thick, but they were very large in diameter. The springs were very strong, and the hands were very stout. Therefore, the power that moved the hands was much greater than the power that moves the hands in the watches that are made to-day.
The boys prepared a board, a b c d, Fig. 6, about a foot square. Toward the upper edge, at e, they scooped out a place large enough for the watch to drop into, and have the face even, or flush, with the surface of the board. The face of the watch was then fastened to the board. The crystal was opened, or taken away entirely, and thus the hands traveled around just as if they had been on the board itself. A small wooden lever, j g, was fastened to the board by a nail, f, that acted as a fulcrum. Another lever, g i, had a fulcrum at h, and touched the first lever at g. The board was kept at a slant on the table by the prop n, or else by a pile of books behind it. The lever g j was so adjusted that the minute-hand of the watch would pass over the end, j; but when the given hour-hand, v, for instance, came
