( <5 i ) 
they would be by the Adion of Gravity, if its force 
were applied upwards 5 for by that force alone, the 
Globes woutd not be ftopt, till they had mea^fured 
Spaces equal to the heights above thercfifting Subftance, 
from whence they fell ; which heights bear a great Pro- 
portion to the depths, the Globes in this Experiment 
are immerfed into the yielding Subftance, as I have 
found upon trial 
Thus, if I miftake not, may be removed the Difficul- 
ty attending this Experiment. But as Mr. Leihitzs 
Opinion is deduced from it by Means of this Axiom, 
that Effeds are proportional to their Caufes ; fo that 
here the Effeds being thought the fame, the Caufes 
are concluded to be lo likewife ; it will not be a- 
mifs to mention in this place an Experiment, where 
'this Axiom may be more jnftly applied, than it can be in 
our prefent cafe, from which Experiment the received 
Opinion may be proved. This Experiment is men- 
1 tioned by Polenus from Merfenms^ though tried by him 
fomewhat rudely; but has been often fince made in 
I the following manner. To one end of the Beam of 
.a Ballance is hung a Weight, and from a proper 
1 height is let fall upon the other extremity of the 
Beam another Weight, which by Briking thereon 
ihall raife the end, to which the Weight is fufpended, 
to fuch a height, as is juft fufficient to fet free a cer- 
itain Spring, if then a different Weight be bung in 
I the room of the former; the height, from whence the 
' fallingWeight muft defcend,in order to raife the Extremi- 
ity'of the Ballance, to which this otherWeight is fufpend- 
>ed, to the fame height as before, that is, high enough 
I to fet the forementioned Spring at liberty, is found to 
Ibe fuch, that the Velocity, with which the falling 
Weight ftrikes upon the Ballance, in this latter Cafe, 
iwill be to its former Velocity, as the latter Weight 
