Popular Science Montlihj 



193 



Forcing an Automobile Into the 

 Air with a Stream of Water 



IT was not until an 

 Angeles ran into a 

 it off and sending a 

 shooting up into the 

 air, that some resident 

 motion-picture direc- 

 tors thought of in- 

 corporating the idea 

 in one of their thrillers. 

 Had they known that 

 in practically every 

 shooting gallery in the 

 country, one of the 

 most popular targets 

 is a ball suspended at 

 the top of a stream of 

 water, they might have 

 staged the same thing 

 years ago. But even 

 though the idea was a 

 bit old, it served their 

 purpose. 



With two poles, a 



The auto- 

 mobile went 

 up and down 

 like an ele- 

 vator but the 

 water didn't 

 have the 

 least thing 

 to do with it 



automobile in Los 

 hydrant, breaking 

 column of water 



donkey engine, cables, a hydrant and an 

 automobile filled with actors, a stream of 

 water was actually made to give the im- 

 pression that it was holding up the car in 

 the air. The car was attached to a 

 crosspiece and it was hoisted up and down 

 by the donkey engine. 

 Water from the hy- 

 drant just touched the 

 bottom of the car. 

 Of course, the hoisting 

 apparatus did not ap- 

 pear in the picture. 

 All one saw was the 

 frightened occupants 

 in the car shooting up 

 and down on the top 

 of a powerful jet of 

 water. 



Showing the donkey engine, 

 and one of the two poles to 

 which the cables were attached 



Estimating Ship-to- 

 Shore Distances 



PROFESSOR J. 

 JOLY, of Dublin, 

 has suggested an in- 

 genious method of 

 measuring distances by 

 wireless. He relies on 

 the fact that disturb- 

 ances travel with differ- 

 ent speeds in different 

 media. Sound travels 

 eleven hundred feet or 

 more a second in air 

 and about forty-seven 

 hundred feet a second in water, while wire- 

 less or light signals travel at equal speeds. 

 Thus, if a shore station sends out these 

 different signals at the same time, they 

 will not be received by the ship simul- 

 taneously; there will be an interval of 

 time between them that will increase as 

 the distance of the ship from the shore 

 increases. If a mile from the station, a 

 ship would receive a sound signal in air 

 4.5 seconds later than a sound signal in 

 water, and an air sound 5.5 seconds, or 

 a sound in water 1.2 seconds, later 

 than a wireless signal. Therefore, 

 with a knowledge of the interval 

 » which elapses between the recep- 



tion of any two of these different 

 signals, it is a comparatively 

 simple matter to calculate the source from 

 which they have been sent. Knowledge 

 of arithmetic is all that is necessary. 



