[ 3 6 7 1 
top to the bottom of the tube, and eleCtrifed the air- 
pump as before : and it was a moft delightful fpeCta- 
cle, when the room was darkened, to fee the electri- 
city in its paflage ; to be able to obferve, not, as in 
the open air, its brufhes or pencils of rays an inch or 
two in length, but here the corufcations were of the 
whole length of the tube between the plates ; that 
is to fay, thirty-two inches, and of a bright filver hue. 
Thefe did not immediately diverge as in the open air, 
but frequently, from a bafe apparently flat, divided 
themfelves into lefs and lefs ramifications, and refem- 
bled very much the mofl; lively corufcations of the 
aurora borealis. 
At other times, when the tube has been exhaufted 
in the mofl; perfect manner, the eleCtricity has been 
feen to pafs between the brafs plates in one continued 
ftream of the fame dimenfions throughout its whole 
length; and this, with a fubfequent obfervation, 
feems to demonftrate, that the caufe of that very 
powerful repulflon of the particles of eleCtrical fire 
one to the other, which we fee in open air, is more 
owing to the refiftance of the air than to any natural 
tendency of the eleCtricity itfelf ; as we obferve, that 
the brufhes thereof from blunt bodies, when the 
electricity is ftrong, diverge fo much, as to form, 
when feen in the dark, an almoft fpherical figure. 
This figure feems therefore toarife from the electricity’s 
endeavouring to infinuate itfelf between the particles 
of air. The figure, that an elaftic fluid of lefs denfity 
muft form, when let loofe, and equably comprefled 
by one more denfe and more elaftic, muft neceflarily 
approach to that of a fphere. 
Upon 
