[ 677 ] 
One may frequently obferve, in difcharging a Ley- 
den vial, that if the two knobs are approached to- 
gether very flowly, a hiding noife will be perceived 
before the fpark ; which /hews, that the fluid begins 
to flow from one knob to the other, before it pafles 
in the form of a fpark j and therefore ferves to con- 
firm the truth of the opinion, that the Ipark is 
brought about in the gradual manner here de-*- 
fcribed. 
A N 
