158 Mtafure of the EleBric Charge . 



4 Mcafures, - Red-hot, and feparated. 

 5 and 6 Mcafures, - Red-hot, and difperfed in globules. 

 Between 8 and 9 Mcafures, - A fpontancous difcharge. 



Experiment 4. 

 THE ele£lromcter being adjufted with the grcateft weight, the difcliarglng-balls were 

 placed at the dilHuce of two inciies. The refults were : 



1 Meafurc, - Luminous particles thrown off. 



2 Meafures, - The fame, with fmoke. 



3 Mtafures, - Red-hot. 



4 Meafures, - The wire was difperfed in red-hot globules. 

 Between 6 and 7 Meafures, - A fpontancous difcharge of the battery. 



Experlitieiit 5. 

 THE apparatus remained as in the fourth experiment, with the addition of another bat- 

 tery, containing 12 feet fuperficial of coated gl.ifs ; and the iron wire placed in the circuit 

 of the difcharge of tliis battery was about 0.08 inches in diameter, and two inches in length. 



TJie refults were : 



I Meafure, - No alteration in the wire. 



4 Meafures, - Luminous particles thrown ofF. 



dvMeafures, - The fame, with fmoke. 



8 Meafures, - Red-hot, and feparated. 



10 Meafures, - Difperfed in red-hot globules. 



Between 15 and 16 Meafures, - A fpontancous difcharge. 



Harley-freet : May 27, 1 797. HENRY HALDANE. 



The eleftrical machine employed in thefe experiments has a glafs cylinder of nearly l8 

 inches in diameter. It was conftrufled by Mr. Nairne, and is a mod powerful inftrument, 

 particularly in exhibiting all tJK phenomena in which the negative, or ele(£lricity of the 

 rubber is concerned. 



V. 



On the Mechattical CenJlruBkn and Ufes of the Screw. 



J_^LEMENTART writers on mechanics, from demonftrations founded on the leading 

 property of the lever, teach us that the adlion of any pc wer to raifc a weight or overcome 

 an obftacle is facilitated by the inclined plane in the proportion of its length to its perpen- 

 dicular height, when the power operates in the direftion of the plane itfelf, or as the hori- 

 zontal bafe t6 the height when the power a£ls in an horizontal direftion. They aifo fhew, 

 by the eafy procefs of applying a right-angled triangle to the furface of a cylinder, that the 

 thread of a fcrew, when its axis is placed in the perpendicular, is in effe£l: an inclined plane, 

 whofe length in one turn is meafured by the portion of the thread itfelf, and height is the 

 diftancc between two contiguous threads : that is to fay, it would be juft as eafy to raife a 

 5 weight 



