( 45 ) 
{hews the fame to be true, fuppofing the elaftic Body 
be placed between feveral other homogeneous elaftic 
Bodies, in the State of a violent Equilibrium. For the 
Ufe and Application of all this, he refers ustothe 
third Chapter. 
The XI and XII Proportions deferve particular 
Regard : In the former he defcribes a Machine , by 
which any curious Perfon may enquire into the Phe- 
nomena and Laws of the Propagation of a tremulous 
Motion : In the latter he explains and demonftrates 
the Theory of thofe Propagations, found out by 
the Help of this Machine. The Subftance of them 
is this. 
Suppofe a Series of elaftic Globules or 
B Rings, a, b, c, £fc. in the Line of a 
tremulous Vibration A B, to be kept in 
a violent Equilibrium, an Obftacle being 
placed at A and B. Let us fuppofe alfo, 
the laft Ring a to be comprefled farther 
towards A, &c. foas that the Space left 
in the Line of Vibration may be taken up 
by the others. 
Thefe Things being fuppofed, the Au- 
thor aflerts, that by the Reftitution of 
the comprefled Ring a , the Force im- 
prefled will be propagated through the 
other Rings by an individual Aftion, i. e. 
the Ring a in reftoring itfelf will firft 
aft only upon b , and comprefs it by 
the Difference of the Forces. Then b 
being comprefled, will transfer the Force 
it receives, not backwards, but into the 
Ring 
