LIMITS OF AUDIBLE SOUND. 59 



fine that I am afraid you will not hear it. Here is the semitone below 

 it on the same scale, and although many persons are not able to 

 hear these pipes separately, yet the resulting tone produced* by 

 blowing two together is perfectly audible to most people. This was 

 made many years ago, and it is historically interesting as being an 

 anticipation of modern research on the subject. Among the many 

 discoveries of Professor Wheatstone was one of this kind. He produced 

 the same effect by using two very small harmonium reeds ; reeds of the 

 same kind are here in this small box. These are made by Mr. Gries- 

 bach, but as to priority between the two I am unable to speak. 

 Unluckily, that is the condition of these small reeds also : they are 

 unable to speak, but there they are. Time has damaged them, but 

 the same things were certainly contrived as early, if not earlier, by 

 Professor Wheatstone. Then as to the lower limit of sound. Helm- 

 holtz may have erred from erroneous information given to him, and 

 perhaps the appreciation of musical sound might be rather different 

 in other persons than those he had to experiment with. I believe 

 he is a violin player, but I do not think he pretends to be a musician 

 of a practical kind. He says the deepest tone of musical character 

 which can be heard is about forty-one vibrations in the second, in 

 the upper half of the thirty-two feet octave he says the perception 

 of the separate pulse is clear, but practically he does not admit that 

 you can get any musical note below E or F on the common German 

 double bass. Now what seems to be wanting, if I may use the term, 

 in these investigations, is that the mass upon which he experimented 

 was rather small. He used pianoforte strings weighted with a kreutzer_ 

 in the middle. That is a very feeble source of sound. If we are to 

 produce these low tones, the amplitude of the vibrations must be 

 enormously increased. Whether he has quite utilized the effect of a 

 consonant body or of a resonant case, on a vibrating string, to the 

 extent to which it might be done, is a point on which I have some 

 little doubt, because it has been done here. Here is Elliott's apparatus, 

 originally invented by Chladni, a sort of wand passed through a slit. 

 This Helmholtz alludes to, and declares it produces a false result, 

 because the upper partial tones are very strong compared with the 

 fundamental. No doubt they are. I should be delighted to find him 

 correct, and he is probably speaking only of simple pendular vibrations 



