MEASUREMENT OF THE LOAD. 51 



the last lever. (6) Low power, with two or three levers, 

 and variable moving weights on the last lever. 



III. MANOMETER, OR FLUID PRESSURE MACHINES. It 

 will now be convenient to briefly describe these various 

 types, and to limit the detailed description to the more 

 familiar machines only, and to those with which readers 

 may be likely to come in contact. 



I. SINGLE-LEVER MACHINES. On Fig. 18 are shown, at 

 {a) and (6), diagrammatic views of two representative 

 machines of this type. That at (a) is the Werder machine, 

 largely used for scientific work on the Continent. In this 



FIG. 186. 



machine there is a single bell-crank lever ; the ratio of the 

 length of the long arm to that of the short one is extremely 

 laro-e, so that very small weights placed on the scale pan, at 

 the outer end of the large arm, produce correspondingly 

 great levers on the specimen at S. It will be noticed that in 

 this machine, on account of the lever being a right-angled 

 one, the pull on the specimen is horizontal. 



The machine shown at (6) has a straight arm and com- 

 paratively low leverage, so that the weight or weights W 

 must be large. In some machines of this type the weight 

 W is invariable in magnitude and acts as in a steelyard, the 

 pull on the specimen depending upon the position of W 



