XL ADMINISTRATIVE REPORT [eth. ann.20 



Mechanics 



111 classifiyiug industries as those of substantiation or those 

 of construction, we were compelled to use terms with specific 

 meanings, and we selected the terms used because they seemed 

 to be the most available for that purpose and because there 

 seemed to be no terms in use for the industries which we 

 wished to discriminate. Manufacture etyinologically means 

 "making by hand." In nil industries the hands are used to a 

 greater or less extent, and the term is used with this wider 

 significance, so that its etymology and wider use alike forbid 

 its employment to signify what we desire when we adopt the 

 term construction. In the case of mechanics we have a term 

 which is already used in science for the purpose we wish, sig- 

 nifying the industries which have for their purpose the utiliza- 

 tion of powers. 



The mechanical devices, as forms which are employed in 

 the utilization of powers, are the hammer, the lever, the wedge, 

 the wheel, and the pulley. 



^ hammer is a device for condensing the motion of a pon- 

 derable body through a space in a time and expending it in 

 an instant; or it may be defined as the method of expending 

 gathered momentum in the instant of impact. 



A lever is an instrument which is used witli a fulcrum to 

 move a weight by taking advantage of the motion in an arc 

 of a larger circle in the correlative arc of a smaller circle, so 

 that the force of the long arm is expended in the short arm. 

 A smaller mass is thus made to move a larger mass, but the 

 smaller must move a greater distance. A hammer which is 

 used for percussion is often supplied with a handle, which is a 

 lever with a fulcrum in the edge of the hand. Thus the long 

 arm of tlie lever is next to the hammer, and the momentum 

 of the hammer is increased thereby. 



A wedge is an inclined plane used to subdivide the distance 

 of the weight moved into minute parts. The wedge itself is 

 usually employed in conjunction with the hammer, the wedge 

 beinjj a device for subdividing- the distance moved, and the 

 hammer being used to take advantage of the force of jjer- 

 cussion. 



