7 8 fbe Inclined Plane. [Book I. 



but may in fact be confiderably lefs, if thefe weights 

 dj d t draw in the direction D e, parallel to the inclined 

 plane. But if thefe weights draw in the direction 

 D F or D E, they necefTarily lofe a part of their force, 

 as will appear from what has been already advanced 

 on the fubject of obliquity, in treating ofpullies, &c. 



Hence it is evident, that the power ads to the 

 greateft advantage when the line of traction, or the 

 line in which the body is drawn, is in the direction 

 D e y parallel to the inclined plane. When thus fi- 

 tuatcd therefore, there will be an equilibrium, when 

 the power is to the weight of the body, as the height 

 of the plane is to its bafe. In other words, the me- 

 chanical advantage gained by the inclined plane is in 

 proportion as the length of the plane exceeds its 

 height*. Thus if a weight of four ounces is laid on 

 an inclined plane, the length of which is to its height 

 as 2 to i, it will be counterbalanced by a weight 

 of two ounces drawing in the line D e (fig. 2.) pa- 

 rallel to the plane; or if the length of the plane is to 

 its height as 4 to i, the body will be fuftained by one 

 ounce only. Hence in drawing a cart or waggon up 

 hill, if the power of the horfes bears the fame propor- 

 tion to the weight of the waggon, as the height of the 

 hill to its declivity, then the waggon will not run back, 

 and a fmall additional fcrce will enable it to advance. 



V. The WEDGE, which is alfo one of the fix fimple 

 machines, is of a triangular form ; the thinned part 

 is called the point or edge, and the thicker the head or 

 bafe of the wedge. 



The action of the wedge agrees mo(t with that of 

 the inclined plane. It is made ufe of to cleave, to 



* Adams's Le&ures, vol. iii- p. 295. 



/ raife, 



