HYDRAULIC MACHINERY, FOR MINES 



841 



. If the velocity at the surface and in the middle of a stream be 88 inches, 

 what is its velocity at the bottom, and what is its mean velocity ? 



Square root of 36 = 6, 



Double this root, 6x2 = 12. 



36 + 1 12 = 25 inches per second velocity at bottom. Am. 



Again, 36 4- -5 6 = 30'5 inches per second mean velocity. Ans. 



WEIRS AND KECTANGULAB NOTCHES. The following Table V. gives the number of 

 cubic feet of water per minute that will pass over a weir for each inch in width, and 

 from 1 to 19 inches in depth. 



Let the weir be 10 inches in depth; opposite 10 inches the second column is 12-747, 

 being the number of cubic feet discharged per minute 1 inch in width. Then again, 

 suppose the weir 6 1 inches deep. The figures answering to this number are 6-488, 

 which is cubic feet discharged per minute for 1 inch in width. By multiplying the 

 number of cubic feet discharged per inch in width by the width of the weir in inches, 

 the total discharge per minute will be obtained. Note. The water should be set back 

 to a dead level before it passes over the weir-board, and the depth taken at a point 

 before the curve commences. 



SCOUR OF WATERCOURSE BEDS. 



Water running at a velocity of foot per second will scour ./we clay 

 J fine sand 



J coarse sand 



1 ., fine gravel 



2 feet 



shingle 1 inch diameter 

 ' 3 angular stones as large 



as an egg 



5 conglomerate 



DISCHARGE .BY HORIZONTAL PIPES. 1st. The less the diameter of the pipe, the less 

 is the proportionate discharge of water. 



2nd. The greater the length of the discharging pipe, the greater the diminution of 

 the discharge. 



3rd. The friction of water is proportionally greater in small than in large pipes. 

 4th. The velocity of water flowing out of an aperture is as the square root of the 

 height of the head of the water. 



DISCHARGE BY VERTICAL PIPES. The discharge of fluids by vertical pipes is 

 augmented on the principle of the gravitation of falling bodies ; consequently, the 

 greater the length of the pipe, the greater the discharge of the fluid. 



INCLINED PIPES. A pipe which is inclined will discharge in a given time a 

 greater quantity of water than a horizontal pipe of the same dimensions. 



