G4G 



Pupular Science Montlilij 



COUNTING DEVICE 

 .REMOVABLE CAP 

 CLAMP 



A mechan- 

 ism in the 

 handle counts 

 the jumps 



Letting the Jumping Rope Record 

 the Jumps 



Al.l. the vocal gymnastics 

 . have been taken out of 

 the youthful pastime of jump- 

 ing rope. No longer will 

 numbers be called as the prod- 

 igy next door jumps up to 

 five hundred or more, and the 

 chances are that "Pepper, sail, 

 mustard, cider, vinegar," will 

 be forgotten. Two inventors ot 

 New Brunswick, New Jersey, 

 Edward H. Stokes anci Ray- 

 mond E. Grymes, have inven- 

 ted a jumi^ing-rope wJiich will 

 automatically rejiister the num- 

 ber of times it is turncil. In 

 other words, children can jump 

 themselves to death without 

 uttering a sound. 



In a handle at one end of the 

 jumping-rope is a counting 

 mechanism which registers 

 each turn of the rope. The 

 handle is hollow so that the 

 rope enters it and connects 

 with the counter at the front 

 end. A removable cap makes 

 it possible to adjust the coun- 

 ter. A sight opening is provided 

 in the side of the handle to 

 enable the jumper to note the 

 nuniber (if I urns. 



i dangerous ns 

 is exciting 



Why You Hear Well on a Clear, 

 Frosty Night 



S( lENCE says that the loudness of 

 xiunds varies inversely as the square 

 ot the distance. This is merely another 

 way of saying that if you walk three 

 times as far away from the source of the 

 sound as you were liefore, its loudness 

 will be not one-third what it was, but 

 one-ninth what it was, for nine is the 

 fquare of three. 



On the other hand, the density of the 

 medium which conveys sound is very im- 

 portant. On a frosty night the air is 

 dense. One consequence of this is that 

 an automobile runs better, because the 

 engine gets larger supplies of oxygen. 

 Another result is that sounds are heard 

 luore loudly. Howexer, the report of a 

 gun high up in the mountains is like 

 the sound of an exploded firecracker. 

 In the Colorado Rockies giant boulders 

 are carried along b\' snow slides. On 

 a warm night the slides make little 

 noise, but on a clear, frosty 

 night the noi-^^e is deafening. 



Increasing the Thrills in 

 Ice- Skating 



SKlI.Fbb skating on ice is 

 tlilVicult enough with ordi- 

 iiar\- skates but with stilt-skates, 

 such as those illustrated, it is in 

 a class with dangerous sports. 

 The ice is hard enough w hen hit 

 frt)m the usual height. How 

 must it feel when stilt-skates skid 

 out from under yoii? 



There arc only three people in 

 the United States who have 

 attained proficiency in the art 

 of skating on stilts. C. P. Mul- 

 d<ion, who appears in the illus- 

 tration, is one of them. His 

 stilts arc twenty-four inches high 

 and carry a steel plate at the top 

 and bottom 



There arc nine parts to the 

 skating apparatus, adjusted to 

 suit the skater. Actording to 

 thosi' who ha\e used stilt-skates 

 tlie>- are just as safe as ordinar>- 

 ice-skates, and the>' give just as 

 nuich jileasure and comfort. There 

 is no dciuing the fact that they 

 afford |)leasure; but as for com- 

 fort — that is for professionals. 



