800 



Popular Science Monthly 



Cleaning Spark-Plugs with Phono- 

 graph Needles 



THE usual way to clean spark-plugs 

 is to take them apart and scrub 

 them with a brush after scraping them 

 with a knife. An 

 easier and quicker 

 method is here de- 

 scribed. Secure a 

 small cylinder open at 

 one end, into which is 

 fitted a bushing with 

 threads corresponding 

 to those on the ends pmonographI 

 of the plugs. After fill- NEEDLE5- 

 ing the cylinder about Phonograph 

 half full o£ gasoline, J«*n depoTi? 

 throw in a dozen or 

 more old phonograph needles, then screw 

 the plug in the cylinder. After giving it 

 a good shaking, remove the plug. The 

 end will be thoroughly cleaned, more 

 thoroughly than if it were scrubbed and 

 scraped in the usual way. — Peter J. M. 

 Clute. 



SPARK PLUG 



DU5niNG- 

 CYLINDER 



A Good Permanent Base for Small 

 Battery Switches 



NO doubt many an experimenter and 

 many a student in an electrical 

 school has had the misfortune to break 

 the frail wood base of a battery switch. 

 A switch made like the accompanying il- 

 lustration will last almost indefinitely. 



Take a piece of J^-in. fiber, 2J^-in. 

 square and place it in the chuck of a small 



A battery switch base turned from fiber 

 makes a substantial mounting for the parts 



lathe, and recess the bottom 2 in. in 

 diameter and % in. deep, as shown in the 

 sketch. Before removing the fiber from 

 the chuck, drill a 3/16-in. hole in the 



center, remove it from the chuck and put 

 a 3/16-in. bolt into the center hole and 

 lock it with a nut of the same size. The 

 bolt is then put into the chuck, and the 

 outside is turned round. 



The radius of the switch lever and the 

 size and the distance apart of the switch 

 point holes must be determined from the 

 style of switch from which the parts are 

 taken. — Walter B. Weber. 



This Lighthouse Sends Radio Fog 

 Warning Far Out to Sea 



POINT JUDITH LIGHT, near New- 

 port, R. I., is now equipped with a 

 radiophone fog-warning machine. The 

 words "Point Judith Light!" are repeated 

 every five seconds and can be heard any- 

 where within a radius of about eight 

 miles. After every third warning the 

 words "You are getting closer; keep off!" 

 are sent out. These can be heard about 

 two miles away. 



Wave lengths keep changing continu- 

 ously between 550 and 650 meters, in 

 order that operators on passing ships 

 may be more likely to hear the messages 

 even if at the moment they may not be 

 tuned exactly to a standard wave- 

 length. The system is likely to be im- 

 proved at intervals. All lighthouses could 

 profitably employ such a contrivance if it 

 works out well in practice. 



Opera Hat with Enclosed Electric 

 Light for a Sign 



FROM a French inventor comes an 

 advertising sign in which an opera 

 hat is its housing. The sides of the hat 

 are cut so that letters are removed that 

 spell out the words of the sign. These 

 letter holes are covered over with a thin 

 light fabric of the same color as the hat. 

 When unlighted the letters remain in- 

 visible, but with one or more battery 

 lamps placed inside and lighted, the hat 

 becomes a conspicuous advertisement. 

 The batteries may be carried in the pocket 

 and wired under the coat to the neck 

 and up to the hat over the hair on the 

 back of the head. The current can be 

 flashed on and off with a switch in the 

 coat pocket. This is a real novelty in 

 advertising signs and one which would 

 be sure to attract attention. 



