760 



A 



Popular Science Monthly 



T 



Show-Window Advertising Device 



Operated by Gas Bubbles 

 H K device 



acidulated water of the tank, gas coming 

 oil froni the plate and rising so as to 

 till the small bell. 



illustrated is 

 based on the move- 

 ment of a body 

 caused by electro- 

 lytic action. In a 

 glass tank of liquid 

 is placed a celluloid 

 or other disk which 

 floats upright. On 

 its top is a small 

 bell-shaped body of 

 any material. A 

 metal plate is 

 mounted at the 

 middle of the disk 

 and a wire leads 

 down from it and 

 projects below the 

 disk. The end of 

 the wire dips into 

 bottom of the tank, 



/BLonmo PAP£^ 



M£RCa/=<Y 



The disk rises to the top of the tank where 

 the gas escapes, causing the disk to sink 



mercury 

 and thus 



at the 

 makes 



electric contact so that an electrolytic 

 action is set up. 



The metal plate is attacked by the 



The gas contained 

 in the bell increases 

 the buoyancy of 

 the float and causes 

 it to rise to the top 

 of the tank, where 

 the gas escapes out 

 of a fine tube at the 

 top of the bell. 

 The gas could not 

 escape at the bot- 

 tom due to capil- 

 lary action, but at 

 the toj) of the tank 

 the end of the tube 

 comes against blot- 

 ting paper and the 

 gas escapes because 

 the capillary effect 

 at the end of the tube is destroyed. When 

 the gas escapes the float descends again 

 to the bottom of the tank, and the action 

 is repeated. An advertisement can be 

 put on the disk, or letters can be used. 



Money Prizes for Motorcyclists 



Send In Your Kinks 



IF you are a motorcyclist, if >()U 

 have devised simple wa>s of mak- 

 ing repairs, if you have improved 

 >(nir machine in any wa\-, this will 

 interest you. 



The Popular Science Moxthly 

 offers a first prize of $25, a second 

 jirize of $15 and a third prize of $10 

 for articles in which motorcyclists will 

 describe and illustrate the methods 

 which they ha\'e successfully cm- 

 ])io\c'd for overcoming trouble, for 

 making (|ui(k repairs by the roadside 

 or more ditlicult repairs in the shop, 

 or for making attachments broaden- 

 ing tiie use of the motorcyle. 



The three prizes will be awarded by 

 the editors of the Poi'l'L.VK SciliNCE 

 MoMULV in the order of merit. 

 W iiat is more, even though your 

 article ma>' not win a prize, the edi- 

 tors may buy it at the usual rates, just 

 licr.insc it is so good. 



There are no limitations to this 

 prize offer. We don't care for fine 

 ]ihrasing, init for mechanical ideas. 

 Rough pencil drawings or jihotographs 

 will do for illustrations. 



ObserN'e these conditions: 



(i) .Xrtick's must be written on one side 

 of the .sheet only. 



(2) Write your name and address in the 



upper right-hand corner of the first 

 sheet. 



(3) Enclose postage for ihc return of llu- 



manuscript. 



(4) Don't send in arlicles on ideas which 



have already been published. 



(5) Uon't send paper ideas — tilings thai 



you haven't aclualK' done \ourself. 



(6) .Xcidress the envelopes containing 



arlicles to 



"Motorcycle Contest Editor" 



I'lintAK Siii:\(ic MoNrnrv 



239 Fourth Ave., New York City 



The contt'st will close on ni'comhrr 



