2&"i Mr. Nicholson’s Experiments and 
31. Achard’s experiments with a number of pointed cc nes, 
fcrewed in a plate of metal, and likewife the pointed apparatus 
defcrihed (par. 29 ) fhew that the effecl of points depends on 
the remotenefs of their extremities from the other parts of the 
conduftor. This leads to the following general law. 
In any electrified conductor the tranjition or efcape of electricity 
-will be made chiefly from that part of the fur face which is the 
moft remote from the natural fate . 
Thus in the apparatus of the ball and Idem, the point hav- 
ing a communication with the reft of the whole condu&or, 
conftantly poffe fifes the fame intenfity ; but the influence of 
the furrounding furface of the ball dimi nifties its capacity. 
This diminution is iefs the farther the ball is withdrawn, and 
confequently the point will really poflefs more ele&ricity, and 
be more difpofed to give it out when it is prominent than 
when deprefifed. The fame explanation ferves for negative 
electricity. 
32. The effeCt of a pofttive furface appears to extend farther 
than that of a negative : for the point a£ts like a ball when 
confiderably more prominent if it be pofitive than it will if 
negative. This property was ufed by me fome years ago for 
the conftruCtion of an inftrument to diftinguifti the two elec- 
tricities 
For the fake of concifenefs I pafs over many faCts which 
have prefented themfelves in the courfe of my experiments on 
the two electricities, and content myfelf with obferving, that 
there is fcarcely any experiment made with the pofitive power 
which will not afford a refult worthy of notice, if repeated 
with the negative. 
* Introduction to Natural Philofophy, Vol. II. p, 320. 
33. When 
