CENTRAL SCIENTIFIC CO., CHICAGO, U. S. A. 



473 



No. 12954. 



No. 12962. 



No. 12956. 



STOP-WATCHES 



FOR TIMING A SINGLE PERFORMANCE. 



12954. STOP-WATCH, Ordinary Design. Xickeled case, stem wind, lever escapement, % second divi- 

 sions. Convenient for testing and experimental work, being non-magnetic $11.00 



12956. STOP-WATCH, Decimal Design. The minute is divided into 100 parts so that the watch is very 

 useful in all timing operations in which the minute is the unit of time. Readable to % of a 

 division, L e., 1/300 minute. Otherwise same as No. 12954 described above 11.00 



FOR TIMING TWO EVENTS WHICH START SIMULTANEOUSLY BUT END AT 



DIFFERENT TIMES. 



12960. STOP-WATCH. Xickeled case, stem wind, lever escapement, % second divisions, non-magnetic, 

 provided with two hands for timing two events which start simultaneously but end at different 

 times. Useful in timing laboratory operations, and in timing first and second places in a race. 

 Has a higher grade movement than Xo. 12954 25.00 



FOR TIMING AN INTERRUPTED PERFORMANCE. 



12962. STOP-WATCH. Xickeled ease, stem wind, lever escapement, 7 jewels, % second divisions, non- 

 magnetic. This watch is operated by moving a "side piece" instead of pushing the "crown." 

 This method is easier on the mechanism, giving the watch much longer life. It also operates 

 more smoothly than the old style and will record the time of an interrupted performance, 

 giving exactly the time used for the performance itself, excluding the interruption. The hands 

 will come back to their original starting point only by pushing the "crown" 12.50 



12966. STOP-WATCH, DeLay, Electrically Operated. A high grade American made stop-watch, with 

 an electromagnet attachment by means of which the starting and stopping of the watch may 

 be accomplished. 



The watch is a seven jewel movement in a nickeled case. A chronometer with stop-watch attach- 

 ment is used, as this type of stop-watch is more rugged and reliable. The chronometer is a 

 good time keeper and the electromagnet attachment does not in any way interfere with the use 

 of the watch as a time keeper or as an ordinary stop-watch. 



This device is very useful in many laboratory experiments, such as the accurate determination 

 of the velocity of moving bodies and the timing of various operations by automatically opening 

 and closing the electric circuit. 



