( 830 
and other more fubtile bodies, and returns by it^elafticity to 
its former place, then^are thefe parts extruded with violence as 
from the center of that place, and communicate their motion as 
far as the found is heard. Or, when any folid body is moved 
whha fudden and violent motion, thefe parts muft be afFefted 
thereby: For,as thefe parts are fo much refifted by folid bodies 
as to (bock them ; fojon thecontrary^ they muft needs be mo- 
ved by the fudden darting of folid bodies. 
So that (according tohm^Scu^idn^^y becaufed by the trem- 
ble of folid bodies without the prefence of^r^jj? Airjand alfoby 
the reft itution of grofs Airjwhen it hath been divided with any 
vioIence.Thus^ffaith hejwe fee,that a Bell will found in the Tor' 
ricellian fpace ; And ^ when the Air is divided with any fudden 
force,as by the end ofaWhip having all the motion of the Whip 
contrafted in it, and by a fudden turn throwing off the Air ; or 
by accenf3on,as in Thunder and Guns 5 or by any impreffion of 
force carrying ic where other Air cannot fo forcibly follow, as 
uponcomprefTingof Air in a bladder till it breaks, or in a Pot- 
gun 5 a fudden crack will be caufed. 
Having laid down this Hy pothefis,and left his Reader to ap- 
ply it to the d.foxG'mmi\Qx\^d ph^nomem i he proceeds to the 
DifcourfeofM^^/^ it felf,and maketh it a confiderable part of 
hisbufinefs to fiiew, How this A6ion that caufes Sound^ is per- 
formed by the feveral Inftruments of Mufuk 5 having taught his 
Reader,^r/?, WhataTi>»eis,and that the Tones ufeful inMufick 
are thofe within the Scale^m which they are placed as they have 
relation to one another, ^'(r^t);^^/;',^ here in confifts that Relation 
of tones union of mixt Sounds. Which done, he explains, 
how tones zxG produced, and what alfjftances are given to the 
Soundty InJlruments.WhtYc he teaches, that wherever a Body 
ftands upon a Spring that vibrates in equal Terms^fucha Body, 
put intomotion^will produce a Tone, which will be more grave 
orrf^«/i', according to the velocity of the returns : Wherefore 
Strings vibrating have a Tl?;^^ according to the Bignefs or Ten- 
fion of them 5 and Bells that vibrate by crofs Ovals , produce 
Notes according to the bignefs of them, or the thickncfs of 
their fides; and fo do all other bodies, vvhofe fuperficies, being 
difplaced by force, refults or comes back by a fpring which 
carries it beyond its firft ftation. And here^to make it to be un- 
derftood,how every pulfe upon fuch vibrations c^ilf€S Sound , 
our Author gives us to confider,that thegrofs Air is throv^ncff 
by the violence of (hcmofion^which continues fomemomen sof 
time 
