126 ELECTRICITY. [LeSSOH XXI. 



bring it to within an inch of the smaller end of the 

 tobacco pipe, and by moving the glass gently 

 round in an horizontal circular track, you will 

 cause the pipe to turn round on the watch- 

 glass as the needle turns on its centre in a mari- 

 ner's compass. 



A great many experiments may be performed 

 with the help of an Electrical Machine ; which may 

 be bought, with the necessary apparatus, at the 

 shop of any philosophical-instrument maker in 

 London : but, as it is probable that several persons 

 may wish to try Electrical Experiments, who can- 

 not well afford to purchase a more complete appa- 

 ratus, I shall here give a description of a very sim- 

 ple machine, and one that may be made at but 

 little expense. It consists of two plates of a cir- 

 cular form ; the under plate may be of wood, glass, 

 or brass, five inches in diameter and covered on 

 the upper side with an even coat of melted sealing- 

 wax of the second quality. The upper plate may 

 be made of wood, coated entirely with tin-foil, 

 having a handle of baked wood, or glass, fixed in 

 the centre of its upper surface. Or it may be 

 made of tin, wired a^id soldered round the edges 

 on the upper side, with a small socket in the cen- 

 tre for fixing the handle. The socket and handle 

 may be coated with melted sealing-wax dissolved 

 in spirit of wine. If the under plate be made of 

 wood, glass, or sulphur, it may be coated on 

 the under side with tin-foil, fixed on with stiff 

 paste. / 



To use this machine : First, with a dry, warm 



piece 



