( 2o8o ) 
The Explication of the firji Figure. 
Between thetw6 loweft Lines, you have the Series 
of all the 12 half Notes in an OGave^ from Are to 
Alatnire, which added together make an Odave or exaft 
Daple Proportion : Thefeveral parts alfo added together 
make all thofe intervals cf which it is conftituted. As for 
example, the two half Notes from A to A ^ f|, and from 
A ^ to B U make a Major Tone 1 3 to which if an Hemi* 
tone from B to C jh be added, you have a IcfTer Third |. 
In like manner between the two next lines, you have 
the fcries of all the 1 2 half Notes, in an Odave from 
C fa ut to C fol fa ut : the two fir ft Tones added toge- 
ther make a greater Third : and fo you may add a Tone 
or Hemitone till you arrive at every interval in the 
Oftave, which fo calFd becaufe eight founds are required 
for expreffing thofe feven gradual fteps whereby we com- 
monly afcend to it. 
It may be alfo obferv'd, that the proportions falling 
upon the fame Notes in two Keys, one finger-board will 
be fufficient for botk 
9 acknowledgd by all that are acquainted either 
i with Speculative or Praftical Mufiek,that every inter 
valis divided into two parts, whereof one is greater than 
the other : An Eighth i into a Fifth f and a Fourth 
Again, a Fifth ^ into a greater Third ^ and a leifer Third |, 
Thus alfo a greater Third ^ muft be divided into a 
Tone Major | and a Tone Minor xV The Lefler Third (to 
comply with the praftice of Mufick) is rather compounded 
of. than divided into a Tone Major | and an Hemitone^ 
which is its complement, 
Three Tones Major, * two Tones Minor, and two of 
the foreftid Hemitones, placed in the order found in the 
Scheme, exadly conftitute the praftical 0-3:ave: which 
is fo caird becaufe it confifts of eight founds, that con- 
tain the fcven gradual intervals. But it is alfo neceffary 
to 
