Prof. A. M. Mayer's Researches in Acoustics. 513 



the ball at a place much nearer to the central axis than that at 

 which it entered. 



Then, if the reflecting- p6wer of our nebulous ball is so far 

 weak that the rarer portions of matter, which receive the rays 

 singly (as is the case on the side nearest to the sun), are not 

 luminous to our eyes, it is yet quite possible that the portion 

 equally rare on the side furthest from the sun may be luminous 

 to us, because upon that a large number of these rays are con- 

 centrated as by a magnifying glass. This part will thus have 

 the appearance of a tail on the side furthest from the sun. 



In those few comets which have also a short tail pointing 

 towards the sun, we may suppose that the refracting-power of 

 the matter is so far greater that some of the rays meet in a focus 

 before they reach the centre. 



When the tail is curved or otherwise irregular, it may be that 

 the ball is not a perfect sphere. 



The above hypothesis, in the hands of some one better able 

 to work it out, might perhaps be made to explain that interest- 

 ing appearance the comet's tail. 



Yours obediently, 



32 Highbury Place, Samuel Sharpe. 



November 19, 1874. 



LXIX. Researches in Acoustics. — No. V. 



By Alfred M. Mayer. 



[Concluded from p. 452.] 



5. Six Experimental Methods of Sonorous Analysis described 



and discussed. 



^F\HE remarkable discoveries in sound made in these later 

 -i- times by Helmholtz were owing in great part to his having 

 early seen the necessity of obtaining precise knowledge of the 

 composition of sounds (by means of the methods of sonorous 

 analysis which he had devised) before one could attempt to 

 give an explanation of the causes of timbre, of the mechanism 

 of audition, and of the physiological causes of musical har- 

 mony ; and, furthermore, he reduced all of the analytic methods 

 and explanations contained in his classical work to a harmo- 

 nious system, by showing how they naturally flowed from the 

 fertile theorem of Fourier. As Helmholtz distinctly states, 

 "In letzer Instanz ist also der Grund der von Pythagoras 

 aufgefundenen rationellen Verhaltnisse in dem Satze von Fou- 

 rier zu finden, und in gewissem Sinne ist diese Satz als die 

 Urquelle des Generalbasses zu betrachten" (Tonempfindungen, 

 p. 346). 



Phil. Mag. S. 4. No. 321. Suppl Vol. 48. £ L 



