280 Mr. Nicholson’s Experiments and 
the fparks ceafed to ftrike as before, and the extremity of the 
electrified conductor M exhibited negative figns, and ftruok the 
fide of the other conductor. And when one conductor was 
eleCtrifiedy>/^r and the other minus , fig. 6. both figns appeared at 
the fame time, and continual ft reams of eleCtricity paffed between 
the extremities of each conductor to the fide of the other con- 
ductor oppofed to it. In each of thefe three cafes, the current 
of eleCtricity, on the hypothefis of a fingle fluid, paffed the 
fame way. 
28. In drawing the long fpark from a ball of four inches 
diameter, I found it of fome confequence that the ftem fliould 
not be too fhort, becaufe the vicinity of the large prime con- 
ductor altered the difpofition of the eleCtricity to efcape ; I 
therefore made a fet of experiments, the refult of which 
fhewed, that the difpofition of balls to receive or emit eleCtri- 
city is greateft when they ftand remote from other fur faces in 
the fame ftate ; and that between this greateft difpofition in 
any ball, whatever may be its diameter, every pofiible lefs 
degree may be obtained by withdrawing the ball towards the 
broader or lefs convex furface out of which its ftem projeCls, 
until at length the ball, being wholly depreffed beneath that 
furface, lofes the difpofition entirely. From thefe experiments 
it follows, that a variety of balls is unneceffary in eleCtricity ; 
becaufe any fmall ball, if near the prime conductor, will be 
equivalent to a larger ball whofe ftem is longer. 
29. From comparing fome experiments, made by myfelf 
many years ago, with the prefent fet, I confidered a point as a 
ball of an indefinitely fmall diameter, and conftruCted an in- 
ftrument confifting of a brafs ball of fix inches diameter, 
through the axis of which a ftem, carrying a fine point, was 
fcrewed. When this ftem is fixed in the prime conductor, if 
the 
