761 



PLATE IV. 



Ti-;. 51. The weiglit A, acting on the double cylin- 

 der H, supports the weight C by the pulley running in 

 the angle of the rope D C E, which is wound on the 

 larger cylinder nt D, while it is uncoiled from the 

 smaller at E, and the force is the same as if the weight 

 C were attached to the lineC F, acting on the axis F, 

 of which the diameter is equal to the difference of the 

 radii of the double cylinder. P. 63, 206. 



Fig. 52. A single fixed pulley, supporting two equal 

 weights. P. 68. 



Fig. 53. A single moveable pulley, by means of 

 whicfi a weight supports another twice as great. P. 

 68. 



Fig. 51. The arrangement ofpuUies in ships' tackles, 

 with a force of six to one. P. 69. 



Fig. 55. An arrangement of puUies in a vertical 

 line, with a force of six to one. P. 69. 



Fig. 56. Mr. Smcaton's blocks, giving a force of 

 twenty to one, the rope being applied in the middle 

 of the outer series, and following the order of the fi- 

 gures from 1 to 21. P. 69, 207. 



Fig. 5l. A system of puUies fixed on one axis in 

 each block; having a power of 8 to 1. P. 69. 



Fig. 58. A system of pullies, each of which doubles 

 tlie effect; having a power of 8 to 1. P. 69. 



Fjg. 59. A system of pullies with each rope fixed to 

 the weight, having a force of 7 to 1. P. 69. 



Fig. 60. Two systems of pullies, of the kind dcuomi- 



natcd Spanish bartons, in which two of the pullies arc 

 suspended by the same rope: the one has a power of 

 4, tlieother of5. P. 69. 



Fig. 61. A. The depression of the middle weight be- 

 ing one third of its distance from tlie pullies, it sustains 

 two equal weiglits," which are together three times as 

 great as itself. B. The depression of the smaller 

 weight being one fourth of its distance from the pulley, 

 it supports a weight twice as great as itself. P. 70. 



Fig. 63. A joiner's saw, stretched by twisting a 

 double cord, by means of a lever passing through it. 



Fig; 63. The weight A, resting on an inclined plane 

 of which the height is to the oblique length as 3 to 5> 

 is sustained by a weight B three fifths as great as itself; 

 and if for the resistance of the plane we substitute the 

 action of the weight C, reduced to the direction AT) 

 perpendieular to the plane, this weight must be four 

 fifths of the weight A, the- horizontal length of the 

 wedge being four fifths of its oblique length. P. 70. 



Fig. 64. The weights A, B, and C, acting, by means 

 of threads passing over pullies, wliich are fixed to any 

 required part of a horizontal table, on the rollers 

 which press against the sides of a wedge, proportional 

 in length to the respective weights, retain each other 

 in equilibrium, when their directions meet in one point. 

 In order that the threads may pass on each side of the 

 wedge, it may be supported by three or more balls.. 

 P. 71. 



