287 



SECTION IX. 



CORRESPONDENCE, 1856-66. 



To Sir John Herschel. 



Camden Street, June 8, 1856. 



MY DEAR SIR JOHN, I have long had the idea of a piano- 1856. 

 forte in which each set of strings belonging to one note is to 

 communicate with a pipe for resonance ; and sometimes I have 

 thought that a spring at the mouth of a pipe struck by a 

 hammer would make a good instrument. In this case we might 

 have various pedals opening and closing the upper end of the 

 pipe. But I never imagined anything so grand as the intro- 

 duction of a vast force by means of electro-magnetism. I should 

 propose to call your instrument the electro-magnetic whack-row- 

 de-dow. 



What is the reason why thirds and sixths, major or minor, 

 are more pleasant to the ear than fourths and fifths, which are 

 consonances of simpler ratio of vibration ? Fifths, by them- 

 selves, have a certain something which the ear does not like 

 much of, and consecutive fifths we all know are forbidden. But 

 thirds and sixths are very pleasant. If Dr. Smith's theory of 

 beats be true, I almost suspect I spy a way to explain this. But 

 I must get hold of an organ tuner, and learn whether they are 

 actually effective. 



Yours very truly, 



A. DE MORGAN. 



To Sir John Herschel. 



7 Camden Street, August 15, 1856. 



MY DEAR SIR JOHN, What can you say for yourself? Your 

 last note was written in a good strong hand. This is hot 

 weather. When I was a boy I read how Cato the Censor used 

 to allow himself a little vinegar in his water when the heat was 



