[ lop 3 
enough to be fpedfically lighter than the lower Air, 
as the great Halley hzs fagacioufly conjedured. Or 
if the upper Parts of the Air, as being lefs faturated 
than the lower Parts, may be able to draw them up- 
wards, till the Excefs of Weight, which is conftantly 
increaling, is equal to the Excefs of Attradion. 
PROPOSITION III. 
Bodiesy made EleBrical by rubbing, do themfehes 
repel one another, or the eleBrkal excited Bodies 
themf elves repel one another » 
Experiment I. 
The two Fragments of Tubes before- mentioned 
being fufpended horizontally, and in a Pofture pa- 
rallel to each other, I held in one Hand, and with the 
other rubbed fome time ; then gently letting them go 
fo as to be at Reft, I could plainly perceive them 
recede from each other towards that End which had 
not been taken hold of. 
But as upon repeated Trials I found it difficult to 
make this Experiment fucceed unexceptionably, the 
Tubes generally having fome reciprocating Motion 
of their own, after quitting the Hand, I made ufe of 
the following Method. 
I fufpended a lingle little Tube about a Foot long, 
by a long blue ftlk Line, perpendicularly, and upon 
a Table placed my great Tube fixed in a Stand as 
before, excited each alternately, two or three times 5 
* Prop. II. Exper, VIII. 
then 
