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128 CLASSIFICATION OF ORGAN PIPES. [V. §§ 63, 64.
63. The reader should observe that, in the course of this discussion, we have incidentally obtained a more complete theory of resonance than could be given in chapter m. When a tuning-fork is held at the orifice of a tube, the strongest resonance will be produced if the note of the fork coincides with the fundamental tone of the tube. A decided, though less powerful, resonance ought also to ensue if the fork-note coincides with one of the higher tones of the tube, which, as we know, are all overtones of its fundamental. A resonance-box is only a stopped1 pipe under another name. We may therefore employ it to test the truth of our result, that the only tones obtainable from a stopped pipe are the odd partial-tones of a clang of which the first is the fundamental-tone. I possess a series of forks giving the first seven partial-tones of a clang. When I strike 1, 3, 5 or 7, and hold them before the open end of the stopped resonance-box corresponding to 1, a decided reinforcement of their tones is heard. If I do the same with 2, 4, or 6, hardly any resonance is produced. Thus our theoretical result is experimentally verified.
64. Organ pipes are divided into two classes according as their sounds are originated.
1 For forks of high pitch it is, however, found [best to use resonance-boxes open at both ends, and therefore corresponding to open pipes. |
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