52 SECTION PHYSICS. 



perfect of all, perhaps, is the key-board of Mr. Bosanquct. Tie uses 

 fifty-three sounds to the octave, and I believe he has them all there 

 present for use. But he is here to-day, and has kindly undertaken to 

 explain the subject, in which he is much better informed than I am ; he 

 has also undertaken to mention to you the key-board of Colin Browne, 

 Ewing Professor in the Andcrsonian Institution of Glasgow, of which, 

 by Mr. Browne's kindness, I have a model. The real instrument is 

 only just patented, and is not completed. As soon as one is com- 

 pleted, Mr. Browne tells me he will kindly send it to this Exhibition 

 for inspection by visitors. Between these elaborate contrivances 

 of mechanism and the simple unaltered key-board there lie two 

 others. The first is that proposed by Professor Helmholtz, and 

 the second, which I hoped to be able to exhibit, but am unfor- 

 tunately prevented, is that of Mr. Ellis, the translator of Helmholtz, 

 whom I have just mentioned. He uses a combination stop system, and 

 it may be some consolation to us to know that the harmonium would 

 have shown very little ; that is to say, only the ordinary twelve notes. But 

 there are stops added, each of which draws out the proper com- 

 bination for the particular key. This, of course, lays you open to 

 the difficulty that the combination stops cannot be always drawn 

 rapidly during performance, and in extemporising or playing compli- 

 cated music you do not always know what key you are going to travel 

 into, and therefore what stop to draw. If the key-board is before you, 

 you can in a moment choose the right one, your very ear directs you 

 to it. Of this I have a specimen sent from Paris. It is termed Gueroult's 

 Harmonium, but it is practically, I believe, equivalent to the system 

 suggested by Helmholtz. There are twenty-four notes to the octave, 

 simply arranged on two key-boards, one above the other, like the key- 

 board of an organ, but close together so as to enable the finger of the 

 hand to touch the proper key of either range. The description of it I 

 have before me is as follows, if you will pardon a rough translation : 

 The' two key-boards are tuned each in true fifths ; but the posterior 

 key-board is tuned a comma lower than the anterior key-board, which 

 is, in the diapason normal, the French pitch. I need not go into the 

 account closely, but you can consider some notes as flats instead ol 

 sharps, and then considered as flats, the keys on the second key-board 

 represents the sharps on a third key-board, which would be tuned a 



