THE INCLINED PLANE. 4S| 



eKftnple of this kind, you will perceive, that by raising the 

 weight an inch, there are four ropes shortened each an inch, 

 and therefore the hand must have passed through four inches 

 of space in raising the weight a single inch ; which esta- 

 blishes the maxim, that what is gained in power is lost in 

 space. 



The next mechanical power is the wheel and axle, which 

 consists of a cylinder, and a wheel fastened to it, or of a cy- 

 linder with projecting spokes. The power being applied at 

 the circumference of the wheel, the weight to be raised is 

 fastened to a rope that coils round the axle. The advantage 

 gained is in proportion as the diameter of the wheel exceeds 

 that of the axle, Svmpose a wheel to be twelve feet diame- 

 ter, and the axle one K>ot^ the power acting at the circumfe- 

 rence oFthe wheel moves over twelve times the space which 

 the circlnifercnce of the axle dbes, 'Hence, twelve hundred 

 weight may be raised with the power of one hundred weight. 

 The wheel and axle maj^e considered as a perpetual lever, 

 the centre of the axle being" the fulcrum, half the diameter 

 of the wbeel th€ long arjm, and half the diameter of the axle 

 the shor^m. Nowj'^frbm this it is evident, that the greater 

 the diarifeter of the wheel, and the smaller the diameter of 

 the axle, the stroller is the power of this machine ; but then 

 the weight mu^ rise slower in proportion. A useful appli- 

 cation of the wheel and axle is the Cran@. used on^harfsfor . 

 drawing goods up from a ship. A man sets a great wh©^ 

 in motion by pressing on the spokes at the rim, and the rope . 

 to which the goods are attached is wound round the axl^ 

 The wheel is sometimes put in motion by a man in 4he imF 

 side, who is in an upright position, and keeps walking on tlio 

 bars, as if ascending stairs, wh^eh keeps the wheel revolving. 



The inclined plane is nothing more than a slope, or de- 

 clivity, frequently used to facilitate the drawing up of weight?. 

 The increase of the power is in the proportion of the length 

 of the plane to its height ; that is, the more the plane is 

 lengthened, or its height shortened, the less is the resistance 

 to be overcome. If a plane be twenty feet long, and the 

 perpendicular height be four feet, or one-fifth of the length, 

 then five hundred pounds would be balanced on it by one 

 hundred, because the plane is five times the length of the 

 perpendicular height to which the weight is to be raised. If 

 the height be two feet, or one-tenth of the length, then fifty 



