ISO THE POWER BEHIND THE ENGINE 



of water would pass any given point each second, but since 

 the velocity of the water is 2 feet per second, 30 cubic feet 

 will represent the amount of water which will flow by a given 

 point in one second. 



175. Quantity of Water Furnished by a River. Drive stakes 

 in the river at various places and note the time required for 

 a chip to float from one stake to another. If we know the 

 distance between the stakes and the time required for the chip 

 to float from one stake to another, the velocity of the water 

 can be readily determined. 



The width of the stream from bank to bank is easily meas- 

 ured, and the depth is obtained in the ordinary way by sound- 

 ing; it is necessary totake'a number of soundings because the 

 bed of the river is by no means level, and soundings taken at 

 only one level would not give an accurate estimate. If the 

 soundings show the following depths .'-30, 25, 20, 32, 28, the 

 average depth could be taken as 30 + 25 -f 20 4- 32 + 28 -f- 

 5, or 27 feet. If, as a result of measuring, the river at a given 

 point in its course is found to be 27 feet deep and 60 feet 

 wide, the area of a cross section at that spot would be 1620 

 square feet, and if the velocity proved to be 6 feet per second, 

 then the quantity of water passing in any one second would 

 be 1620 x 6, or 9720 cubic feet. By experiment it has been 

 found that I cu. ft. of water weighs about 62.5 Ib. The 

 weight of the water passing each second would therefore be 

 62.5 x 9720, or 607,500 Ib. If this quantity of water plunges 

 over a ro-ft. dam, it does 607,500 x 10, or 6,075,000 foot pounds 

 of work per second, or 11,045 H.P. Such a stream would be 

 very valuable for the running of machinery. 



176. Windmills. Those of us who have spent our vacation 

 days in the country know that there is no ready-made water 

 supply there as in the cities, but that as a rule the farmhouses 

 obtain their drinking water from springs and wells. In poorer 



