96 The Cultivation and Preparation of Coffee 



near the centre of the stream. The water 

 runs faster there than elsewhere. Near the 

 bottom and at the sides it flows more slowly. 

 The difference depends upon the nature of the 

 channel. If it is a wooden trough with smooth 

 sides and bottom, take off 15 per cent. ; if a 

 channel made of bricks, 17 per cent. ; if the 

 bottom and sides are earth, 29 per cent. In 

 rough mountain streams 36 per cent, must be 

 taken off the speed. 



Take the average speed of the stream to be 

 100 feet per minute, and the channel to have 

 earthen bottom and sides, and the area of the 

 stream 18 square feet. First correct the speed, 

 by reducing it 29 per cent., and 71 feet per 

 minute is left. Multiply this by 18 feet area, 

 and the answer is 1,278 cubic feet per minute. 



It will be seen that, owing to the great 

 variation in the size and character of various 

 channels, this method of measuring water can 

 never be more than approximate. 



Another method of ascertaining the quantity 

 of water is from the overflow on a weir, or 

 where no weir or bye- wash exists, planks may 

 be put across the stream and a rectangular 

 notch made (see illustration) sufficiently 

 wide and deep for the whole of the water to 

 pass through. The water should be dammed 

 back until it is as nearly as possible in the 

 condition of a still reservoir, having little or no 



