Men and Horses in moving Machines. 

 Table. 



285 



This Table proves to us that the size of the inen em- 

 ployed to raise the weights vertically has considerable influ- 

 ence on the height to which they brought the san^e weifht. 

 We find also by this l!uu the height diminishes in a much 

 more considerable ratio than the vieigh. increases ; and we 

 may therefore conclude, that it is advantageous to employ 

 large men when it becomes necessary to draw vertically 

 from below upwards : and on the contrary, it is more ad- 

 vantageous to employ men of a considerable weight, when 

 it is required to lift up loads by means of a pufley about 

 which a cord passes, that the workmen draw in a vertical 

 direction, from above downwards. To find the absolute 

 strength of tiiese men in a horizontal direction 1 took the 

 following method. 



Having fixed over an open pit a brass pulley extremely 

 well made, of 15 inches diameter, whose axis, rnade of well 

 polished steel to diminish the friction, was |- inch in dia- 

 meter; J passed over ihis pulley a silk cord worked with 

 care to give it both the necessary strength and flexibility. 

 One of the cuds of this cord carricd-a hook to hang a 

 weight to it which hung vertically in the pit, whilst the 

 other end was held by one of the 20 men, who in the first 

 order of the following experiments made it pass above his 

 shoulders; instead of which, in the second, he simply held 

 it by his hands. 



I had taken the precaution to construct this in such a 

 manner thai the pulley niiglu be raised or lowered at plea- 

 sure, in order to keep tiie end of the cord held by the man 

 always in a horizontal direction, according as the man was 

 lall or short, and cxeiled his strength in any given direction. 

 T3 Jhati 



