VOL. XLVm.] PHILOSOPHICAL TRANSACTIONS. 4'21 



hand, .nnd afterwards approacliing the tube, sometimes with his finger, and at 

 Other times with a key, they observed very small explosions, which were little 

 more than just sensible. 



Mr. W. then desired one of the doctor's servants, who also stood upon the 

 floor, to lay hold of the suspended apparatus on which the doctor was mounted, 

 while the friction of the globe was continued. Immediately on Mr. W. ap- 

 proaching the tube as before, with his finger, and then with the key, a very great 

 difference was observed; for now the explosion was very large compared with the 

 former trials. Dr. le Monnier desired the experiments might be repeated: which 

 was done several times, and to all appearance the differences were the same. He 

 was perfectly satisfied that the experiments were fairly made, and that the explo- 

 sion was much greater when the apparatus communicated with the earth, than 

 when it communicated with the air only. 



hill. Electrical Experiments, with an Attempt to Account for their Several Phe- 

 nomena, jitso some Observations on Thunder-clouds. By John Canton, M.A., 

 F.R.S. p. 350. 



Exp. 1. — From the ceiling, or any convenient part of a room, let 2 cork- 

 balls, each about the size of a small pea, be suspended by linen threads of 8 or 

 9 inches in length, so as to be in contact with each other. Bring the excited 

 glass tube under the balls, and they will be separated by it, when held at the 

 distance of 3 or 4 feet ; let it be brought nearer, and they will stand farther 

 apart ; entirely withdraw it, and they will immediately come together. This ex- 

 periment may be made with very small brass balls hung by silver wire; and it will 

 succeed as well with sealing-wax made electrical, as with glass. 



Exp. 2. — If 2 cork balls be suspended by dry silk threads, the excited tube 

 must be brought within 18 inches before they will repel each other; which they 

 will continue to do, for some time, after the tube is taken away. 



As the balls in the first experiment are not insulated, they cannot properly be 

 said to be electrified : but when they hang within the atmosphere of the excited 

 tube, they may attract and condense the electrical fluid round about them, and 

 be separated by the repulsion of its particles. It is conjectured also, that the 

 balls at this time contain less than their common share of the electrical fluid, on 

 account of the repelling power of that which surrounds them ; though some 

 perhaps is continually entering and passing through the threads. And if that be 

 the case, the reason is plain, why the balls hung by silk, in the 2d experiment, 

 mvist be in a much more dense part of the atmosphere of the tube, before they 

 will repel each other. At the approacli of an excited stick of wax to the balls, iu 

 the first experiment, the electrical fire is supposed to come through the threads 

 into the balls, and be condensed there, in its passage towards the wax : for, ac- 



