318 Elefiricd [Book IV, 



my late valuable friend, Mr. Adams, in his treatife of 

 ekdricity. 



Fig. i. and 2, Plate XXVIII. reprefent two electrical 

 machines of the moft approved conftruction ; the only 

 difference between them is, the mechanifm by which 

 the cylinder is put in motion. 



The cylinder of the machine, Fig. i. is turned round 

 by two wheels, a b, c d y which act on each other by a 

 catgut band, part of which is feen at e and/. 



The cylinder in Fig. i. is put in motion by a fimple 

 winch, which is lefs complicated than that with a 

 multiplying wheel (Fig. 2) : as, however, both ma- 

 chines are fo nearly firnilar, the fame letters of refer- 

 ence are ufed in defcribing them both. ABC repre- 

 fent the bottom board of the machine, D and E the 

 two perpendicular fupports, which fuflain the glafs cy- 

 linder F G H I. The axis of the cap K paffes through 

 the fupport D ; on the extremity of this axis either a 

 fimple winch is fixed, as in Fig. i. or a pulley, as in 

 Fig. 2 *. The axis of the other cap runs in a fmall 

 hole, which is made in the top of the fupporter E. 



O P is the glafs pillar to which the cufnion is fix- 

 ed ; T a brafs fcrew at the bottom of this pillar, which 

 is to regulate the preflure of the cufhion againft the 

 cylinder. This adjufting fcrew is peculiarly advan- 

 tageous : by it the operator is enabled to leffen or in- 

 creafe gradually the preffure of the cufhion, which it 

 effects in a much neater manner than it is poffible to 

 do when the infulating pillar is fixed on a Hiding 

 board. 



* Mr. Adams, in his Leftures on Nat. Philofophy, obfervcs, 

 that machines turned by a fimple winch are lefs liable to be out 

 of order than thofe which are turned by a multiplying wheel, and 

 may alfo be excited more powerfully. Adams's Lefi. vol. iv. 



On 



