i 9 o THE POPULAR SCIENCE MONTHLY. 



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 corain & in both the 

 alarm-clock and the time-lock. Indeed, it was so nearly a combina- 

 tion of the two that we must take away from the more modern invent- 

 ors 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, abed, 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 A, and 

 touched the first lever at g. The board fras kept at a slant on the 

 table by the prop n, or else by a pile of books behind it. The lever 

 gj 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 



