C ^7 ) 
11. A Treatife of the Natural Grounds and Frin^ 
cipks of Harmony. By Will. Holder,^ D. D. 
&c. Lood. in OSlavo. 16^4. 
IN the Introduilioa the Reverend Author Obferves^ 
that Sounds, the material part of Hirmony, are Na- 
tural and Phyfical; buc the difpofiogof them fo as to 
delight the Hearing, is the formal part of it; both uni- 
ted make Harmony compleat , and miy be either in 
Symphony, where many founds are heard together, or 
Solitary, where the Ear finds the Agreements of lln- 
gle preceding with Tdbfequent Harmonious Notts by 
expedtation. The Phyfical Reafbn of this pkafiog A- 
greement of Sounds is the defign of this Trad. In 
order to which, 
In the Firft Chapter he confiders the Nature ofSoands 
in general, and therein agrees with the bed Philofophers 
that Sound is made by a tremulous motion of fome bo- 
dy which communicates it to the ambient x^ir, w^heocs 
'tis propagated in a Sphere by a Temporaneous progref- 
five motion of the parts of the Air at the rate of 276 
Paces in a fecond Minute of time, which is fometimes 
violent enough to break Glafs Windows, and being re- 
flefted by refifting ObjeiJs makes Echoes. If the tre- 
mulous motion be uniform, it makes a Mufical Note or 
Sound; if difform, aNoife; and the Mufical Sounds 
are differenced by the refpedive quicknefs of their tre- 
mulous moticns. 
In the Second Chapter he more efpecially confiders 
Harmonious Sounds, and fliews that the quicker tremu- 
lous motions make the Mufical Sound more acute, the 
flower, more grave. And from the proportions of thefe 
Motions to ea^h other proceeds the Harmony or Drf- 
cord 
