ELECTRIC EFFECTS OF FRICTION. ^ 



covererl with an insnliitini; varnish, and solidly fixed into 

 the wooden base, 1, 1. The different kinds of rubbers 

 must press with different decrees of force, according to 

 their nature, and yieWl always easily to the inequalities of 

 the spindles. For these purposes, a part of the pres- 

 sure is exercised by one or two additional brass sprinjjs, 

 as at 17, pressing on the main spring iG, The brass piece 

 13, by the wire 18, serves as conductor from the different 

 rubbers to the gold-leaf electroscope 19. Another wire, 

 fixed to the same piece at the point 20, projects from it, 

 and is terminated by a hook 21 : this hook is to receive, oc- 

 casionally, the hook 22, of a wire belonging to a glass tube 

 tilled with water 23, the other wire of which is hooked to 

 thepnweco«r?MC?or at the point 24. The hook 22 is com- 

 monly held up by a silk thread, passing over an insulated 

 pulley 25, and stopped at the bottom by a bead fixed to > 



the thread, in a notch of the brass piece 26 : the bead is 

 disengaged when the hook 22 is to come down into the 

 hook 21. 



Such is the general description of the apparatus, and I Difficult to r*. 

 come to the experiments; beginning this account by those t"ihat of ihe 

 which I had principally in view in its construction, namely, column. 

 to have an electric machine with a power not exceeding that 

 of my electric cohimn of 600 groups, for the purpose of com- 

 paring their correspondent effects. I made many trials be- 

 fore I could bring an electric machine down to so small a 

 power; the following was that which nearly succeeded, 

 though still too strong. 



Exp. 1, The spindle, 5, is here a solid glas^s cylinder Exp !• 

 very little above ^ of an inch diameter; it is covered with 

 sealing wax at both ends, for the [)iirpose of insulating a 

 naked part, about ^ of an inch in length, in the middle of r 

 which the friction is produced. The rubber is a simple brass 

 spring, so bent at its extremity, 16, as to fit the upper part 

 of the g/a«* cylinder. 



This apparatus in fact is an electric machine, with a glass shoNrs the 



cv/i/irftT of only | of an inch diameter; however, small as ^'P'*," ^^'^"^!*y' 

 . . . ,1 of theolecirtc, 



it IS, It must be moved very slowly, or the gold leaves would fliUd acting ml 



have greater motions in striking the sides, than they have^^P^^^* 



ut the extremities of my column of ()00 groups, evtjn in the 



time 



