GRIST AND SxlW-MILLS. 351 



6.128X1.33 (y//-') =: 20.38 gallons of water flowing through 

 the gateway in one fecond of time. The number of cubic feet 

 which iffue through this aperture in the fame time rz 8^y//> 

 (art. 8.) zr SXo.31 25X 1.33 =3.325. which being multiplied 

 by 62.5 pounds, the weight of a cubic foot of water, gives 

 207.8 lbs. for the whole preffure on the upper part of the 

 wheel during the fpace of one fecond ; but the inffantaneous 

 preffure, or force of impaft, where the water firft ftrikes the 

 wheel, is/^^w(art. 10. J =: i. 77X0. 3125X62. 5ir 34.57 pounds; 

 alfo S^/jz=lhc uniform velocity acquired at a the aperture in 

 a fecond, zz 10.64 feet. 



When this mill drives two pair of ftones, the gate is raifcd an 

 half inch higher ; fj being in this cafe nr 1.75 and y//j =: 1.323 

 feet, by which means a becomes z: 30 X 2 or 60 fquare inches, i:: 

 0.417 parts of a fquare foot. The other meafurements remain- 

 ing the fame as above, we Ihall have 



%aq.^/h z=: 27 gallons per fecond, 



8 Oy/h := 4.414 cubic feet per do. 



haw =: 46.5 pounds for the force of impaft, 



and 8^b =: 10.584 feet for the uniform velocity per fecond. 



In Emerfon's Mechanics, and Fletcher's Univerfa! Meafurer 

 and Mechanic, the uniform velocity acquired by falling from an- 

 height zz h, is denoted by s/a/js inftead of is/ hs, which is the 

 true meafure of Its celerity. This circumflance Is not mention- 

 ed with the leafl: view to find fault with thefe authors, but to 

 remove any doubts which may arife In the minds of fuch as are 

 difpofed to perufe thefe calculations. 



BEYDLER's SAW-MILL. 



This mill has a fmall underfliot wheel, commonly called a flut- 

 ter wheel, which is no more than 3 feet in diameter. The depth 

 of the water from its furface to the bottom of the penftock is 

 3 feet, the gateway is 3 feet wide by 6 Inches deep, :z: 1.5 



fquare foot, the mean height of the head or D — -- =z 2.7c feet 



2 

 =: h, and ^/h zz 1.658. The fall from the bottom of the penftock 

 to the place where the water impinges on the float or ladle-board 

 b 10 feet, and 2.75-fii = 13.75, being equal to the whole 



height 



