152 THEORY OP COMPOUKD SOUNDS. 



]nExp. 2d, obferved 1,518; calculated 1,5215, 



3d, 1,537 1,539. 



4th, 1,571 1,5736. 



6th, angle obferved 6° 16' - - -6° 7f\ 

 The angle obferved differs from that obtained by computa- 

 tion, in a greater degree than any of the former meafures ; 

 but, when the difficulty of meafuring this angle with accuracy 

 is confidered, and alfo the greater effect of any incorre&nefs 

 Remaiks. *n the data from which a femiconjugate is computed, I think 



the refultof this, as well of the preceding comparifons, muft 

 be admitted to be highly favourable to the Huygenian theory ; 

 and, although the exiftence of two refractions at the fame 

 time, in the fame fubftance, be not well accounted for, and 

 ftill lefs their interchange with each other, when a ray of light 

 js made to pafs through a fecond piece of fpar fituated tranf- 

 verfely to the firft, yet the oblique refraclion, when confidered 

 alone, feems nearly as well explained as any other optical 

 phenomenon. 



Dr. Smith's 

 theory of com- 

 pound founds j 

 that the pulfes 

 do not obftruct 

 or become con- 

 founded with 

 each other. 



V. 



The Theory of Compound Sounds, By Mr. John Gough*. 



JUr. SMITH, author of the work on Harmonics, takes for 

 granted in his theory of compound founds, that the pulfes 

 which proceed at the fame time from a number of founding 

 bodies, do not clafli, or obftruct one another, in their paffage 

 through the air. According to this hypothefis, each fet, of 

 any number of cotemporary fets of pulfes, ftrikes the ear 

 without being confounded with the reft ; in confequence of 

 which, any number of founds may be diftin&ly perceived at 

 the fame time. On this fuppofition, a compound found is a 

 fenfation rendered variable by the irregular manner in which 

 the pulfes of the conftituent founds fucceed to one another. 

 For, if the intervals of time between two fuccefiive pulfes of 



* Manchefter Memoirs, v. 653. This treatife which was not 

 inferted at an earlier period in our Journal, on account of the pref- 

 fure of other matter, has become of (till more intereft as containing 

 the theory to which the author's late difcuffion with Dr. Young is 

 direaed.-W. N. 



one 



