C '7? ] 
This is the Meaning of the Doftor's Words, when he 
fays, that fome Bodies abforbj and others generate 
Air 5 and the fame Bodies do fometimes abioib, and 
at ether times generate Air. He found more or lefs 
Air in almoft every folid Subftance that he try'd j but, 
what was moft remarkable, he found that the Cal- 
cuius humanus (or Stone taken out of a Man's Blad- 
der) was made up of above half its Weight of Air. 
Some have endeavour'd to folve Elafticity by At- 
trafiion only; as for Example; If the String AB 
(Tab. I. Fig. i.) be confider'd as made up of Particles 
lying over one another in the manner reprefented at 
A DB i it is plain, that if the Point T> be forcibly 
brought to C, the Parts will be pull’d from each 
‘Other ; and when the Force, that ftretch’d the String, 
ceales to ad, the Attradion of Cohelion (which 
was hinder’d before) will take place, and bring back 
the String to its former Length and Situation after 
feveral Vibrations. Now, though this feems to agree 
pretty well with the ^htenomena of a String in Mo- 
tion, it will by no means folve the Elafticity of a 
Spring fatten’d at one End, and bent either way at 
the other, like a Knife or Sword-blade, as in Fig. 2. 
For if fuch a Spring be bent from to a, the Par- 
ticles on the Side C, which now becomes convex, 
will be farther afunder at F, while the Particles at 
jD, carried to the concave Part will come defer 
together; So that the Attradion, inftead of making 
the Spring reftqre itfelf,r will keep it in the Situation 
in which it is, as it happens in Bodies that have no 
Elafticity, where perhaps only Attradion obtains. 
Thus a Plate of Lead, a Plate of Copper, and a Plate 
of foft Iron, ftands bent, 
But 
