On the Vihrations of Musical Strings. -333 



iHume's application of ammonia in the test for the detectiort 

 of arsenic. But as the latter gentleman still asserts his ex- 

 clusive claim to the invention, in a way that impeaches 

 the accuracy of my referrences, I beg leave, for the sake of 

 those readers who would not be at the pains to consult the 

 original documents, to correct a material error of which 

 Mr. Hume has been guilty in quoting his own letter. He 

 infers that he originally suggested the employment of am- 

 monia with the nitrate of silver, from his having used the 

 expression " cr any other alkali*.'" Now it will be found 

 that in the only instance in which that expression occurs f, 

 it is used with reference to a totally different test ; namely, 

 the sulphate of copper ; and has therefore nothing to do with 

 the subject in dispute, which relates entirely to the em- 

 ployment of ammonia with the nitrate of silver. 



After this specimen of Mr. Hume's mode of reasoning, 

 I trust it is unnecessary for me to pursue any further a dis- 

 cussion in which I see no prospect of satisfying his ex- 

 pectations, and which must already have exhausted the 

 patience of your readers. 

 I am, sir. 



Your most ol)edient servant, 



Bernard-Street, Russell-Square, P. M. ROGET. 



Nov. 11, 1S12. 



LIX. On the Vihrations of Musical Strings; with « 

 Mode of ascertaining the Sound producible by any given. 

 Number of Vibrations. By Mr. John Southern. 



To Mr. Tilloch. 



Sir, JVIusic being a subject which has been pretty much 

 entertained in the Philosophical Magazine, you will pro- 

 bably give a place in it to this letter in one of your early 

 numbers; which will much oblige me. 



In reading at various times on this subject, T have ob- 

 served a considerable difference in the number of vibrations 

 a«(signed to the note C in the middle of the n)usical scale. 

 Dr. Smith in his Harmonics says, that D on the organ in 

 Trinity College, Cambridge, made 2G3 vibra ions in a se- 

 cond of time; consequentty C must have made ii34 or 233; 



• His wor'ig are the'e I " The qiiejtiou noems capable of being reduced 

 merely to this; What i« comprthended under such expressions as potass, 

 Umr, Hilda, or (my other alkali i' Does not fliia laiijjUHgo mcluJe amvuria, 

 luTijIvf, slioplites,' anJ moe7trnn at least ?" See ilie Medical and Physical 

 Journ:il for October last, (vol. xxviii.) p. '289. 



+ Medical aud Physical Journal, voU xxviii. p. 4 18, line 34. 



and 



