266 APPENDIX. 



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

 the required velocity. 



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

 velocity by 12, which will 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 hundred 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 in 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 reservoir from which water is to be 

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

 of the surface of the water in the reservoir, above the place of dis- 

 charge, and let D be the diameter of the tube in the smallest part. It 

 is required to find the quantity Q which will be discharged in a second 

 of time. The length and height being given in feet,, and the diameter 

 of the tube in inches, the fonnula, when the quantity is required in 

 gallons, is as follows : 



Q = 0.608 -/(D^^). 



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

 the decimal .7854, which represents the difference between the area of a square and 

 of a circle. 



