APPLIED SCIENCE 



which a driving effort is applied by the spring e, and a resist- 

 ance by the spring /. Let the lever have a fulcrum or bearing 

 in the element b to which the elements e and / are jointed, 



making a complete or self-contained machine. This system is 

 a self-strained frame, with one stiff bar, namely, the lever. The 

 bar in this, as in the other drawings, may be regarded as the 

 symbol of a stiff frame, the form or design of which is unim- 



