Page:Popular Science Monthly Volume 88.djvu/721

 Popnlar Science Monthly

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���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.

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