MECHANICS. 125 



preserving the velocity it has acquired, tends to les- 

 sen the irregularity resulting from these causes. 



The effect of a fly, to remove irregularity in the mo- 

 tion of a machine, its weight and diameter being gi- 

 ven, is proportional to its velocity. 



196. In wheel carriages, the equability of the 

 motion is even of greater importance than in hy- 

 draulic engines ; the sudden checks to motion ha- 

 ving a more pernicious effect on an animal body 

 than on an inert mass. 



The improvement of roads, and the diminution of fric- 

 tion, are, in such cases, of the greatest use ; but that 

 which corresponds most to the advantage derived 

 from a fly, is the effect from supporting the weight 

 by springs, or from giving elasticity to the parts by 

 which the cattle are yoked to the carriage. The 

 sudden action of the resistance, and the jerks which 

 are the consequences of it, are thus prevented. The 

 greater the velocity the carriages move with, the 

 more advantage is derived from this application of 

 elastic force. 



SECT, 



