Popular Science Monthly 



903 



© 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! 



■ii^ 



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." 



