Page:Popular Science Monthly Volume 92.djvu/919

 Popular Science Monthly

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��© Kadel & Herbert

This huge bat His place in th

��What Makes the Rum- ble of Thunder?

WHY does thunder rumble? The path of a lightning flash through the air may be several miles in length. All along this path the sudden expansion of the heated air — a true explosion — sets up an at- mospheric wave, which spreads in all directions, and eventuallj^ registers upon our ears as thunder. Since the lightning dis- charge is almost instanta- neous, the sound wave is produced at very nearly the same time along the whole path. But the sound wave travels slowly through the air. Its speed is approximately 1,090 feet per second. Thus the sound from the part of the lightning's path that is nearest to us reaches us first, and that from other parts of the path afterward, according to their distance. Intermittent crashes and booming effects are due chiefly to irregu- larities in the shape of the path.

Making Window- Cleaning Safe

FOR the benefit of window cleaners and painters, Paul Wolff, a Hungarian in Pittsburgh, Pa., has invented a win- dow chair or scaffold, which rests upon the window sill, extending outward and providing the workman with a se- cure support. The de- vice is so arranged that it can quickly be clamped to the window frame and just as readily removed. The win- dow frame is firmly held between a rub- ber-covered hook or brace and the mov- able clamp, which is operated by a screw, like the movable jaw chair damped to

of a vise. with the movable

����like kite is the plaything of a Japanese prince, e world requires distinctive size even in his toys

Giant Kite for the Crown Prince of Sunny Japan

WHILE the Crown Prince of Japan was on his winter vacation at the palace of Numazu he had the huge kite, which is the subject of our illustration, made for his amusement. This monster is in the form of a bird and it measures twenty-four feet from wing-tip to wing- tip. It is capable of attaining great heights and its pull is so powerful that it can lift a man off his feet; consequently, special winding machinery is needed to con- I- trol it.

What American boy would ^ttfK like to swap places with

^^^ the heir to the Cherry-

blossom Empire's throne? Step lively, boys — the line forms on the right!

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��window frame jaw of a vise

��Half Million Words in English Use

THE English vocabu- lary has grown to great size, according to Professor Clark S. Northup, of Cornell University. "The number of words found in old English litera- ture does not exceed thirty thousand; re- cent dictionaries have listed more than four hundred thousand."

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