Mechanic Powers. 35 



it will just balance the weight W; for six multi- 

 plied by two is twelve, as before. And a power 

 equal to three ounces placed at four inches dis- 

 tance from the prop would be the same ; for 

 three times four is twelve; and so on, in pro- 

 portion. 



The statera, or Roman steelyard, is a lever oif 

 this kind, and is used for finding the weights of 

 different bodies by one single weight placed at 

 different distances from the prop or centre of mo- 

 tion D. For if a scale hangs at A, the extremity 

 of the shorter arm, AB, is of such a weight as 

 will exactly counterpoise the longer arm EC ; if 

 this arm is divided into as many equal parts as it 

 will contain, each equal to AB, the single weight 

 P (which we may suppose to be one pound) will 

 serve for weighing any thing as heavy as itself, or 

 as many times heavier as there are divisions in 

 the arm BC, or any quantity between its own 

 weight and that quantity. As for example, if 

 P is one pound, and placed at the first division, 

 one in the arm BC, it will balance one pound in 

 the scale at A ; if it is removed to the second 

 division at two, it will balance two pounds in the 

 scale ; if to the third, three pounds ; and so on 

 to the end of the arm BC. If each of these in- 

 tegral divisions is subdivided into as many equal 

 parts as a pound contains ounces, and the weight 

 P is placed at any of these subdivisions so as to 

 counterpoise what is in the scale, the pounds and 

 odd ounces will by that means be ascertained. 



