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fire is attracted and imbib’d by the balls to fupply 
the deficiency } and that more plentifully at the ap- 
proach of excited glafs, or a body pofitively eledrified, 
than before ; whence the diftance between the balls 
will be increafed, as the fluid furrounding them is 
augmented. And in general, whether by the ap- 
proach or recefs of any body j if the difference be- 
tween the denfity of the internal and external fluid 
be increafed, or diminifhed; therepulfion of the balls 
will be increafed, or diminifhed, accordingly. 
Experiment 5. 
When the infulated tin tube is not eledrified, bring 
the excited glafs tube towards the middle of it, fo as 
to be nearly at right angles with it, and the balls at 
the end will repel each other ; and the more fo, as 
the excited tube is brought nearer. When it has 
been held a few feconds, at the diftance of about 
fix inches, withdraw it, and the balls will approach 
each other till they touch ; and then feparating again, 
as the tube is moved farther off, will continue to re- 
pel when it is taken quite away. And this repulfion 
between the balls will be increafed by the approach 
of excited glafs, jjut diminifhed by excited wax ; juft 
as if the apparatus had been eledrified by wax, af- 
ter the manner defcribed in the third experiment. 
Experiment 6. 
Infulate two tin tubes, diftinguifhed by A and B, 
fo as to be in a line with each other, and about half 
an inch apart ; and at the remote end of each, let a 
pair of cork balls be fufpended. Towards the middle 
Y y of 
