1 R I 



13. The stiffness of rop<s, or the force requisite to bond them has 

 great analogy to friction. In different ropes, the forces requisite to bend 

 them are in the direct ratio of their diameters and their tensions jointly, 

 and in the inverse ratio of the radii of the cylinders round which they 

 are bent 



14. The friction of a rope that is wound round a cylinder increases in 

 geometrical progression, while the number of turns increases in arith- 

 metical progression. 



If the turns be represented by the numbers 0, 1, 2, 3, 4, &c. the resis- 

 tance made by the rope may be represented by the numbers 1, 2. 4, 8, 16, 

 &c. 



15. Though friction destroys motion, and generates none, it is cf es- 

 sential use in mechanics. It is the cause of stability in the structure of 

 machines ; and is necessary to the exertion of the force of animals. 



FRIGORIFIC Mixtures. ( Ure.) 



Tables of Frigortfic Mixtures, sufficient for all useful philosophical 

 purposes. 



FRIGORIFIC MIXTURES WITHOUT ICE. 



N.B. If the materials are mixed at a warmer temperature than 500, 

 the effect will he proportionably greater. 

 123 



