308 



Popular Science Monthly 



Signal Light to Show Gas Turned 

 Off at Oven 



AS MALL manufacturing concern which 

 uses a gas heated enameling oven, 

 found that considerable gas was wasted 

 because the workmen frequently forgot 



Connector on valve lever 

 showing wiring diagram 



to shut off the gas when quitting 

 their work for the night. As a result, the 

 oven burner would be left on all night, 

 with the consequent waste of gas and 

 the liability of overheating and setting fire 

 to the building or of doing damage to the 

 oven and its contents. 



To prevent this, the shut ofif valve on 

 the gas line was provided with an in- 

 sulated extension on the valve handle, 

 as shown in the illustration. Over the 

 end of this insulated extension is placed 

 a metal ferrule which closes the contact 

 between the two metal contact pieces 

 attached to the two wires when the gas 

 is shut off. These two wires form one 

 side of the circuit for the lamp located 

 in the night watchman's office, so that 

 the gas must be shut off before the 

 lamp can be lit. Should the gas be left 

 turned on after working hours, the watch- 

 man is aware of the fact as soon as he 

 comes on duty, as he can only secure 

 light in his office when the gas is shut 

 off from the oven burner. The diagram 

 in the illustration shows the wiring 

 scheme in which a snap switch is used to 

 turn off light after the signal shows that 

 the valve has been closed. 



This signal, while especially built for 

 this purpose, is only suggestive and may 

 be used in many like places us a safety 

 device that will always signal when a 

 certain necessary piece of work must be 

 done on a set time, which may otherwise 

 be forgotten by a careless operator or 

 watchman. — Paul Justice. 



Constructing a Dry Cell Which Can 

 Be Renewed 



PROCURE 1 lb. of chloride of zinc 

 crystals, and dissolve them in about 

 1 quart of distilled water. Stir, until all 

 the crystals pass into solution, adding 

 more water if necessary. After all the 

 crystals have dissolved, pour the solution 

 into a clean vessel, and add enough dis- 

 tilled water to make up 2 quarts. Add 

 1 lb. of sal ammoniac to the solution, and 

 stir it until the crystals have dissolved. 

 Have a vessel ready to receive the con- 

 tents. Then the prepared solution can be 

 set aside for future use, after the vessel 

 has been labeled "battery solution." 



The cell is constructed, as shown in the 

 accompanying illustration, from a zinc- 

 lined can and blotting paper. Moisten 

 the blotting-paper lining with the bat- 

 tery solution, and pour off all excess 

 liquid. Permit the blotting paper to 

 become almost dry. Mix finely powdered 

 manganese and carbon with a small 

 quantity of the battery solution until it 

 has acquired the consistency of a stiff 

 paste. Put the carbon center post in the 

 can, after having covered the bottom of 

 the can with a layer of sand about ^-in. 

 thick. 



The can is then ready to receive 



SUBSTANCt USED 

 IH SeALIHft 



6L0TTIN6 PAPER 

 LININCi 



CARBON ROD 



ZINC sntu 



SQLDIRCO BCfTtOU 



Sectional view of dry cell in which the 

 contents may bQ removed and renewed 



the paste, which should be packed down 

 hard with an improvised ram. The top 

 of the cell should be sealed with paraffin, 

 or a similar substance that can be re- 

 moved easily, in order that the cell may 

 be renewed at any time with little or 

 no trouble. — Herman Neuhaus. 



