Page:Popular Science Monthly Volume 92.djvu/209

 Popular Science Montlihj

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��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.

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