( 6195 J 
ly,) and to the little Cavern and the mouth thereof | and 
how they were able to guide the threds through the paffige 
of that cavero.And having carefully obferved all thefe part^, 
both as they were Joyned together in their rcfpeaiva places, 
and feparate, one by one 5 he tells us, that then he fee upon 
writing thefe Speculations. In which he gives us in the firft 
^hcehis Natural Hijiory of mjick^^ which being the ground 
of the whole work, we think it will not be unacceptable to 
the Reader^to find it here entirely EtjgUjhed ; cfpecially fince 
the Book it fclf is yet very fcarce in £;^^/W, the commerce 
between our and the Italian Stationers being very flow, if 
there be any at alU But before I here deliver this Hiftory, I 
find my felf obliged to take notice, that it, as well as divers 
other parts oi this Treatife, are fomewhat obfcurcly written ; 
which Che Reader of the Book it felf, though he be well verfed 
both in the Language wherein 'tis written, and in the Argu- 
ment , will find to be fo, whenever he (hall have oppor- 
tunity and leifure to read it ; This being premifcd^the Hifto- 
ry it felf follows. 
The Natural Hijiorji of Mufick* 
A Sound begins from the coUifion of two parts of the Air, 
which parting from one another, make a vacuity as to 
Air,in which vacuum two other parcels of Air do meet and 
knock one another : And becaule the two firft parcds of Air 
do incline to return to the center of thecollifion,but cannot, 
becaufe the room is taken upjthey do part from the center by 
lines curled and as 'twere recurring to their firft placcj in the 
doing of which they make a coUifion with thofe parts of the 
Air that have polTeffed themfelvcs oitheir room. And thus 
the fpecies oi the Sound is multiplied and extended. 
Thefe curled lines are more waving near the center of the 
CQHifioD,as being more ftretch't long-ways than fpirally, and 
left waving when they are further off from the center ; in 
which latter lines,thc inclination to return towards the center 
is prevalent above the impetus of receding from it^ fo that 
at laft they turn back towards the center* Thus of thcfpecief 
ofa Sound there is filled a fphere of Air, or fuch a part of a 
fphere of it, as this motion of the Air can without impediment 
fpread it fclf through* ^ 
Eeeceee la 
