192 



SCIENCE. 



[Vol. XIII. No. 319 



converted into an automatic fire-alarm, without in any way inter- 

 fering with its use as a call. Pressure upon the thimble causes 

 electric contact between the springs in the base of the button-fix- 

 ture, in the usual manner, completing the circuit and ringing the 

 bell. 



AN IMPROVED ELECTRIC SYSTEM. 



The Sperry system of electric lighting, which has been widely 

 introduced, especially in the Western States, has recently been 

 considerably improved. The dynamo as now made is shown in 



As a fire-alarm, it operates as follows : When the heat of any 

 loom in which this attachment has been placed reaches a predeter- 

 mined temperature, the alloy melts, and releases the pin, which is 

 forced out of the thimble by the expansion of the spring. The 

 springs in the fixture are then brought into continuous contact by 



Fig. I. A special feature of this is the automatic regulator. The 

 brushes consist of overlapping flat copper strips attached to a 

 movable yoke. This yoke is connected by means of an arm to an 

 electro-magnetic regulator placed in the lamp-circuit. Any vari- 

 ation in the electrical resistance of the lamp-circuit operates the 



' Sperry Dynamo. 



the pressure of the pin, the circuit is thereby closed, and the alarm 

 transmitted to a central station, where measures can immediately 

 be adopted for extinguishing the fire. The device is applicable to 

 open or closed circuit, and to all purposes for which a thermostat 

 is required. It is an efficient substitute for the more complicated 

 and expensive thermostats, and should be very reliable, as the wires 

 and connections are constantly being tested. 



keeper of the electro-magnet. By an ingenious device, this move- 

 ment adjusts the current of the dynamo in proportion to any 

 variation in the resistance of the lamp-circuit. The manufacturer 

 claims that all of the lights, a single light, or any number from zero 

 to full capacity, may be extinguished without danger to the dynamo, 

 and without the presence or knowledge of the dynamo-tender or 

 engineer. 



