APPLICATION OF MECHANICAL PRINCIPLES, ETC. 



99 



he had incurred all the expense and losses of unsuc- 

 cessful trials. 



Even so simple a form as that of an ox-yoke is often 

 made unnecessarily heavy. Fig. 83 represents one 



Fig. 83. 



that is faulty in this respect, by having heen cut from 

 a piece of timber as wide as the dotted lines a c, and 

 being thus weakened, it requires to be correspondingly 

 large. Fig: 84 is equally strong, much hghter, and is 



Fig. 64. 



easily made from a stick of timber only as wide as a b 

 in the former figure. 



In the heavier machipes, it is necessary to know the 

 degree of taper in the different parts with accuracy. 

 A thorough knowledge of science is needed to calcu- 

 late this with precision, but a superficial idea may be 

 given by figures. • If a bar of wood, formed as in a 

 {Fig. 85, p. 100), be fixed in a wall of masonry, it will 

 possess as much strength to support a weight hung on 

 the end as if it were the same size throughout, as b. 



