VOL. XXXVII.] PHILOSOPHICAL TRANSACTIONS. SSQ 



there was very little, if any difference, in the height of the attraction, when 

 there was the same time spent before the attraction was begun in pleno, as there 

 was required to exhaust the receiver. 



A Catalogue of the several Electric Bodies mentiojied above. 



N" Names of the Bodies. Weight. Montli. Days, 



oz. dr. 



1 Fine black rosin 1 January 31 



2 Stone pitch and black rosin. ... 2 2 January 31 



3 Fine rosin and bees-wax 2 1 February 1 



4 Stone pitch ] 7 February I 



5 Stone sulphur 3 6 February 4 



6 Shell-lac 10 O February 10 



7 Fine black rosin ••.... 10 4 February 10 



8 Beeswwax and rosin Q O February 12 



9 Rosin 4, and gum-lac 1 part ..10 O February 12 



10 Sulphur 18 O February 1 5 



1 1 Stone pitch 10 12 February l6 



12 Black rosin 23 O February 23 



13 White rosin 7 12 February 23 



14 Gum-lac 11 14 February lQ 



1 5 Gum-lac and black rosin ana . . g 12 February 26 



16 Gum-lac 4 parts, rosin 1 pt. . . IJ 8 February 28 



17 Shell-lac, fine black rosin ana 28 4 March 2 



18 A cylinder of stone sulphur . . \Q 4 March 20 

 IQ A large cone of stone sulphur 30 O March 29 

 20 A cake of sulphur 11 4 April 29 



An Experiment to shmv that the Friction of the several Parts in a Compound 

 Engine may be reduced to Calculation ; by drawing Consequences from soine of 

 the Experiments on Simple Machines in various Circumstances. By J. T. 

 Desaguliers. N" 423, p. 292. 



The machine consists of three pulleys, 2 upper and one lower, or a tackle 

 of 3, whose diameters are exactly as follows, 2 inches, 1^ inch, 14- inch ; and 

 all the centre pins of \ inch diameter: the rope being of -^ inch in diameter. 



The weight is 1 8 pounds avoirdupois, and consequently the power to keep it 

 in equilibrio must be = 61b., and a very little more must make the power raise 

 the weight, if there was no friction ; but here no less than 20 ounces are re- 

 quired, though the machine is as nicely made as it can possibly be. 

 3z2 



