COMPOUND SOUNDS, &0. 2(57 



If Mr. Gough will take the pains of examining the pheno- The phenomena 

 plena of the grave harmonics, which he feems to have hitherto mon j cs ^ew ** 

 thought beneath his notice, he will be convinced that the coa- that mufkal 

 lefcence of mufical founds is not only poflible, but of very fre- j^nn^ous^ 

 quent occurrence, and that the compound found does actually fiances. 

 " acquire fenfible properties peculiar to itfelf;" and if he will 

 explain, in any other manner than I have done, the indubita- 

 ble fa6t of the audible impreffion of the prefence of the fourth 

 below the key, in confequence of the coexiflence of the fouuds 

 conftituting the interval of a major third, even when both the 

 notes are freed from their harmonics, and when all echo is 

 avoided ; I (hall then liiten to him, with the attention due to a 

 perfon who endeavours to regulate his arguments by there? 

 fclts of accurate obfervation. 



I am, Sir, 

 with great refpeft, 



Your obedient humble Servant, 



XHQMAS YQUNG. 

 Royal Inflitution, May 30, 1802. 



CORRECTION. 

 In your fifth volume (quarto) p. 166, 1. 20, for " a better third 

 than that," read, " equal to the third." 



The following CORRECTIONS made by Dr. Young in his 



Paper on the Meehanifm of the Eye, which is injcrted in our 



fifth volume (Quarto Series) ivere omitted to be mqfr in their 



proper places. 



Page 256, line 6, Prop. III. after e, infert the. bafe being unity.. 



Page 257, line 15, Cor. 10. for ntu, read n 1 1 j line 16, for 

 produft &c. reqd fquare of the collne of incidence. 



Page 258, line 2, Cor. 1 1 . for 1 -f u 7 - — 2 «+, read 2 muu. 



Page 258, Prop. V. Cor. See the note in p. 299. 



|>age 259, Prop. VIII. By a miftake of a fign, the eighth propo- 

 fition is rendered erroneous ; no ufe having been made of that pro- 

 pofition, it has been inferted without proper revifion. It ought to 

 $and thus, with its demon ftration : 



Proposition VIII. Problem. 



To find the path of a ray of light falling obliquely on a fphere, 

 of a refractive denfity varying as any power of the diftance from the 

 <#ntre. 



The 



