Popnlar Science Monthly 



693 



A captive balloon raised above the site of the proposed power plant between the White 

 House and Washington Monument to show how high the stacks would come 



Captive Balloon Teaches a Lesson 



TO demonstrate to the residents of 

 Washington and particularly to 

 the members of Congress, just how 

 unsightly the effect of the contemplated 

 new power plant chimneys really may 

 be, the experiment was made of floating 

 a captive balloon over the site to a 

 height equivalent to that of the com- 

 pleted chimneys. The effect was start- 

 ling, since the balloon, when it attained 

 the height of the proposed chimneys, 

 had soared to an almost unbelievable 

 height. Inasmuch as the new power 

 plant with its undesirable chimneys will 

 have an effect upon the new City Park 

 plan, many people who watched the 

 balloon experiment made up their minds 

 that the chimneys should never be. 

 The question is now under discussion 

 among interested residents. 



How Fast Is Your Train Moving? 



A FAIRLY accurate computation of 

 the speed of a moving train can be 

 (jblained by any keen-eared traveler 

 with the aid of a watch equipped with 

 a second hand. The wheels of a car 



produce a clacking in passing over the 

 rail joints, the succession being divided 

 into measures of as many beats as there 

 are wheels on one side of the car. Further- 

 more, the traveler, due to his position, 

 always hears one beat in each measure 

 accented above the others. To deter- 

 mine the speed of the train, it is neces- 

 sary only to count the accented beats 

 for twenty seconds, the result being 

 approximately the number of miles per 

 hour of travel. 



To explain this, let us say that fifty 

 accented clicks are counted in the 

 twenty seconds. Then the train is 

 making about fifty miles per hour; for 

 the fifty beats indicate that an equal num- 

 ber of rails have been passed over. The 

 standard rail is thirty feet long. Hence 

 fifteen hundred feet are being covered 

 every one-third minute, or two hundred 

 and seventy thousand feet per hour; 

 which, divided by five thousand two 

 hundred and eighty, gives fifty-one and 

 one-seventh miles per hour as the actual 

 speed. It will therefore be seen that 

 the original count (number of beats in 

 twenty seconds) conies close enough to 

 serve the purpose. 



