THE SCREW. 



91 



through which it acts being comparatively small. 

 It amounts only to the distance between two con- 



FJG. 65. 



secutive threads during a whole revolution of the 

 screw On the other hand, the force which turns the 

 screw acts through the circumference of a rather large 

 circle; and, since here also the forces are inversely as 

 the spaces, a moderate turning force produces a powerful 



PIG. 66 (an. %roj., i real size}. 



ition in the direction of the axis. In the screw-press 

 represented in fig. 66, the distance between two con- 

 secutive threads is O m< 01 ; the length of the handle, from 

 one end to the opposite, O m '36. Hence the space 

 described by each extremity of the handle during one 



