5g03' ^''^ 'Thrajtj'mg Ulach'wcs. 



Tl^n the revolution of the drum 

 MultipHed by — • 



Gives tlie revolutions of the drum 326.0 p. minute 



This multiplied by the cireum Terence 4.2 feet 



13040 



The velocity of the drum/, min. 1369.20 



Again, with refpe6l to the fecond machine which he erec.l:ed — ■ 

 The dimenfions of the water-wheel, with its revolutions p. mi- 

 nute, are given — 



A wheel of 96 drives a pinion of 9, on the axle of a drum 

 3 feet diameter. 



Here, —=10.6 revolutions of drum for i of wheel. Suppofc- 



the water-wheel makes 10 revolutions p. minute, this gives 106.0 

 for the revolutions of drum p. m.inute, which, multiplied by the 

 circumference of the drum 9.424, makes 998.9, the velocity of the 

 drum p. minute. Hence it appears, that fuppofmg the water- 

 wheels made 10 revolutions p. minute, then the velocity of the 

 drum in the firil: machine was 1369.2 p. minute, and its velocity 

 in che fecond was 998.9. 



From the above it does not excite furprife, that the drum of 

 3 feet diameter did not thraih fo much as the one of 1 6 inches, 

 feeing that the neceflary velocity v/as altogether wanting. 



I do not pretend to fay, whether thefe machines thrafhed clean 

 or not. I fufped: they would not •, for I never faw one, the 

 circumference of the drum of which did not move with a velo- 

 city exceeding 2000 feet p. minute, that did its work as it ought 

 to be done. Thofe which I have found moit complete, liave the 

 velocity of the drum from 2400 to 2700 feet/>. minute. 



I mud delay the remainder of my remarks to an after occafion, 

 us I do not vviili to eiigrofs too rn ueh of your Magazine, or 

 prevent you from giving the cullomary variety of faVe to your 

 nunicrous readers. Dilflrcnt people have dirlerent talles ; and it 

 is certainly right to gratify tliern as far as circumltances will per- 

 i:ait. I am yours, &c. 



Arator. 



TO 



