444 Apparatus for teaching Mechanics, 



fhaft, &c. are to be moved round. D D. The drum, which has two rims of different 

 circumferences. R. The roller to condu£b the rope. P. The pulley, round which the 

 rope pafles to the larger drum. P 2. Another pulley to anfwer to the fmaller drum. P 3. 

 A pulley through which the rope pafles when experiments are tried with levers, &c. P 4. 

 Another pulley through which the rope pafles when the fledge is ufed. Ro. The road of 

 deal boards for the fledge to move on. SI. The fledge with pieces of hard wood attached 

 to it to guide it on the road. 



Ufes of the Panoi'ganon. 



As this machine is to be moved by the force of men or children, and as their force varies 

 not only with the ftrength and weight of each individual, but alfo according to the different 

 manner in which that ftrength or weight is applied, it is, in the firft place, requifite to 

 eftablifh one determinate mode of applying human force to the machine ; and alfo a me- 

 thod of determining the relative force of each individual whofe ftrength is applied to it. 



To ejlhnate the Force •with which a Perfon can draw horizontally by a Rope over his Shoulder. 



EKperiment i. Hang a common long fcale-beam (without fcales or chains) from the top 

 or tranfom of the frame, fo as that one end of it may come within an inch of one (ide or 

 poft of the machine. Tie a rope to the hook of the fcale-beam, where the chains of the 

 fcale are ufually hung, and pafs it through the pulley P 3, which is about four feet from 

 the ground ; let the perfon pull this rope from i towards 2, turning his back to the ma- 

 chine, and pulling the rope over his flioulder. Fig. 6. As the pulley may be either too 

 high or too low to permit the rope to be horizontal, the perfon who pulh it ftiould be 

 placed ten or fifteen feet from the machine, which will lelTen the angular dire£lion of the 

 cord, and the inaccuracy of the experiment. Hang weights to the other end of the fcale-^ 

 beam, till the perfon who pulls can but juft walk forward, pulling fairly without propping 

 his feet againft any thing. This weight will eftimate the force with which he can draw 

 horizontally by a rope over his ftioulder *. Let a child who tries this walk on the board 

 with dry fhoes ; let him afterwards chalk his fhoes, and afterwards try it with his (hoes 

 foaped: he will find that he can pull with different degrees of force in thefe different 

 circumftances ; but when he tries the following, let his (hoes be always dry, that his force 

 may be always the fame. 



Tojhew the Power of the three different Sorts of Levers. 



Experiment 2. Inftead of putting the cord that comes from the fcale-beam, as in the laffc 

 experiment, over the fhoulder of the boy, hook it to the end i of the lever L, Fig. 2. 

 This lever ispaffed through a focket. Fig. 3. in which it can be fhifted from one of its 



* Were it thought neceflary to make thefe experiments perfe6lly accurate, a fegment of a pulley, the 

 radins of which is half the lengtli of the fcale-beam, Ihould be attached to the end of the beam j upon 

 which the Cord may apply itfelf, and the pulley (P 3.) fhould be ralfed or lowered, to bring the rope ho- 

 rizontally from the man's flioulder when in the attitude of drawing. 



ends 



