[ i8. ] 
May not a Spring of Steel, or other Springs, coh- 
fift of feveral Series of fuch Particles, whofe Polarity 
and *\ttra6tion afting at the fame time, will (hew why 
fuch Bodies, when they have been bent, vibrate, and 
reftore themfdvesi 
If we take a Plate of Steel, and make it fo hot till 
it looks white, and then immediately quench it, we 
thereby fix the Metal in a State very near Fluidity, 
fo that the Particles which the Fire had almoft brought 
to Roundnefs, have but a very fmall Contadt; as ap- 
pears by the Fragility of the Steel thus harden’d, which 
breaks like Glafs, and has a (hort Grain. Steel, thus 
harden’d, is highly elaftic ; for what Workmen call 
hard^ is the moft elaftic : as appears by the Congrefs 
of high-harden'd Steel Balls, which return, in their 
Rebound, the neareft to the Place we let them fall 
from ; and, next to Glafs, have the quickeft Elafticity 
of any thing we know. 
That we may not be thought to have given an im- 
perfedt Account of the Elafticity of a Steel Spring, 
becaufe fuch an one as we have deferib'd wants 
Toughnels, and will immediately fly when bent to 
any Degree ; we mull beg Leave to confider farther 
the Properties of the round Particles, or little Spheres, 
of Steel, in which we have fuppos’d a Polarity. 
Let us fuppofe (Fig. 4;) to be two little Spheres 
or component Particles of Steel, in which, atfirft, wc 
will fuppofe no- Poiarity, but only an Attradtion of 
Cohcfioii. Then, \vhether< the Particles have their 
Contadl at or at <0, f,x, their Cohelion will 
be the fame}, and the lead Force imaginable will 
change theif Contadt from one of thofe Points to 
another i becaufc in the roiling of thefc little Spheres, 
they 
