RULE FOR THE DISCHARGE OF WATER. 285 



Look for the velocity of the water per secoud in the pipe, iu the up- 

 per Ihie ; iiud in the column beneath it, and opposite the given diameter 

 of the pipe, is the height of the column or head required to obtain the 

 required velocity. 



To tind the quantity of water discharged each minute, multiply the 

 velocity by 12, which Avill give the inches per second ; then multiply 

 this product by 60, which will give the inches per minute ; then, to 

 change these cylindrical inches into cubic inches, multiply by 4 and 

 divide by 5.* Divide the cubic inches by 231, and the result will be 

 gallons. 



By comparing this table with the next preceding, we shall perceive 

 that the water flows from three to four, times as fast through the tube 

 two inches long, as through a tube one Jiundred feet long, the diameter 

 of the tube and the head of water being the same. 



RULE FOR THE DISCHARGE OF WATER. 



The following general formula or rule, applicable to different cases, 

 has been furnished by a practical engineer-. It may be useful iu ascer- 

 taining the quantity required to fill the driving pipe of a water-ram, and 

 for various other purposes occasionally occurring in practice. 



Let A represent the fountain or reservoh- from Avhich water is to be 

 conveyed to the trough B through the pipe L. Let JI be the height of 

 the surface of the water in the reservoir, above the place of discliarge, 

 L the length of the tube in feet, and let D be the diameter of the tube 

 in the smallest part. It is required to find tlie quantity, Q, which will 

 be discharged iu a second of time. The length and height being given 

 in feet, and the diameter of the tube in inches, the formula, when the 

 quantity is required in gallons, is as follows : 



Q = 0.608 i/(^ L^ 



This gives the cubic inches very nearly ; but, to be more accurate, multiply 

 the decimal .7S54. which represents the difference between the area of a square 

 and of a circle. 



