244 -Mr. CavAllo’s Obfervatiotis on 
To render this more evident, let two firings equal In every 
refpecl be flruck at the fame time, and they will exprefs the 
fame found precifely, fo that no ear can perceive any dif- 
ference between them, and it is almofl impoflible to diflin- 
guifh whether the found arifes from two firings, or from one 
only, excepting from the loudnefs. But if one of thofe 
firings be fucceffively flopped in different parts of its length, 
whilfl the other remains open as before, and if at every time 
they be both flruck together, their combined founds will be 
found to produce different effects, viz. fometimes more or lefs 
pleafing, and at other times more or lefs difagreeable. When 
the combinations of the two founds are agreeable, they are 
called concords-, and when difagreeable, they are called difcords. 
Experience evinces, that the befl concord is when the length 
of one firing is to the length of the other as i to 2, every 
other circumftance being the fame in both. This proportion 
forms the oclave. The next befit concord is the fifth, viz . 
when the lengths of the two firings are as 2 to 3, after which 
come the proportions of 3 to 4, 4 to 5, 3 to 5, 5 to 6, and 
c; to 3 , for the other concords. The other proportions befides 
thefe are difagreeable in a greater or lefs degree, unlefs they 
are greater than the proportion of 1 to 2 ; but in that cafe it 
will be found, that the proportions which produce agreeable 
combinations are the double, quadruple, odluple, &c. of thofe 
mentioned above, viz. are their odlaves, double odlaves, &c. : 
thus the proportion of 1 to 4 produces a very agreeable con- 
cord, becaufe 1 to 4 is the double of 1 to 2, viz. it exprefies a 
double oclave. 
Secondly, it appears, from the foregoing obfervntions, that 
if we have the length of a firing, or the proportion of a note 
in any part of the firing, we may eafily find its odlaves by 
