Qhfervations on ILleBricity. 2 Si 
the ball be moved on its axis in either diredtion, it caufes the 
fine point either to protrude through a fmall hole in its exter- 
nal furface, or to withdraw itfelf ; becaufe by this means the 
ball runs along the item. The difpofition of the point to 
tranfmit eledtricity may thus be made equal to that of any ball 
whatever, from the minute ft fize to the diameter of fix inches* 
See fig,. 7. let. A. 
30. The adtion of pointed bodies has been a fubjedt of dif- 
cuffion ever fince it was firft difcovered, and is not yet well 
explained. To thofe who afcrihe this effedt to the figure of 
eledtrlc atmofpheres, and their difpofition to fly off, it may be 
anfwered, that they ought firft to prove their exiftence, and 
then fhew why the caufe which accumulated them does not 
prevent their efcape ; not to mention the difficulty of explain- 
ing the nature of negative atmofpheres, If thefe be fuppofed 
to confift of eledtrified air, it will not be eafy to fhew why a 
current of air palling near a prime conductor does not deftroy 
its effedts. The opinion, fupported by the celebrated Volta 
and others, that a point is the coating to an infinitely fmall 
plate of air, does not appear better founded : for fuch a plate 
muft be broken through at a greater diftance only becaufe 
higher charged ; whence it would follow, that points ffiould 
not adt but at high intenfities. I muft iikewife take notice, as 
a proof that the charge has little to do here, that if a ball be 
prefented to the prime condudtor, at the fame time that a 
point proceeds from the oppofite fide of the ball, the eledtri- 
city will pafs by the point, though it is obliged to go round 
the ball for that purpofe ; but it can hardly be doubted, that 
whatever charge obtains in this cafe is on the furface of the 
ball next the condudtor, and not on the remote fide to which 
th§ dedtricity diredts its courfe., r 
31, Achard’s 
