254 Popular Science Monthly 



You Can't Fool the Law of Gravity, One Inner Tube More Than Holds 

 But the Motion Picture Can Up an Automobile 



THE photographs shown below illus- 

 trate one of the cleverest devices 

 ever invented by the modern magicians 

 of the movies. The upper picture is 

 what we see in the studio — a wall and 

 telegraph pole set up at an angle of forty- 

 five degrees. Suppose that the actor 

 wishes to climb the 

 pole and enter one of 

 the windows. Or 

 suppose he wants to 

 slide from the third 

 story window to the 

 ground. Quite sim- 

 ple, is it not? And it 

 would look just as 

 simple and uninter- 

 esting on the screen if 

 the motion picture 

 camera were placed as 

 we should naturally 

 expect it to be placed. 

 But it isn't. That 

 is just where we are 

 deceived. The cam- 

 era is placed at the 

 foot of the incline 

 and pointed upward 

 along the slope of the wall at a corres- 

 ponding angle. 



On the screen we see a perfectly vertical 

 building, with actors 

 climbing straight up 

 from one window to 

 the next, crossing over 

 from telegraph poles and 

 performing the most dif- 

 ficult acrobatic feats. 

 Yet the scene is so con- 

 vincing that we credit 

 the actors with super- 

 human powers in spite 

 of manifest impossibiU- 

 ties. In order to get 

 the full effect of this il- 

 lusion, turn the upper 

 photograph around until 

 the pole is vertical. So 

 long as the law of grav- 

 ity carries no jail sen- 

 tence for its violation 

 the [)ictur(' pf'Oi)le don't 

 mind tamijcring with it 

 photographically. 



H 



OW strong is a rubber tube used in an 



Above: A motion picture climb as it 

 looks in the studio. Below: The iden- 

 tifical climb as it appears on the screen 



The automobile suspended in 

 mid-air by an inner tube 



stretched? How much weight can it lift? 

 These were the questions that vexed some 

 tire manufacturers and they straightway 

 set about to find an answer to them. To 

 the layman it would seem as if the 

 ordinary inner tube 

 couldn't be stretched 

 more than from three 

 to four feet, and, 

 judging by the fre- 

 quency with which 

 tubes burst when they 

 are inflated by care- 

 less persons, one 

 might easily believe 

 that they are ex- 

 tremely fragile. Such, 

 however, is not the 

 case. 



The test which 

 was adopted to prove 

 the resisting qualities 

 of a tube, was a novel 

 and interesting one, 

 as the accompanying 

 illustration shows. 

 An automobile, weighing two thousand 

 four hundred and sixty pounds was en- 

 cased in a frame, bringing the total weight 

 up to two thousand nine 

 hundred and ninety 

 pounds, and the whole 

 was lifted from the 

 ground by means of a 

 block and tackle so ar- 

 ranged that the entire 

 weight was borne by the 

 tube, wliich made up the 

 section immediately 

 above the framework. 

 The tube stretched 

 under the combined 

 weight of the automobile 

 and frame until it 

 reached an uncanny 

 length, but it did not 

 break or split. After 

 the test, it resumed its 

 normal shape and under 

 critical examination ap- 

 peared to be in perfect 

 condition. 



