L20 Mr. D. J. Blaikley onBrass Wind 



Adams in 1876 : and to that paper I am in great measure in- 

 debted. 



A brass instrument may be defined as a resonator capable of 

 reinforcing a certain fundamental periodic vibration originated 

 by the lips, and all such vibrations as have for their relative 

 numbers 2, 3, 4, &c. when the fundamental note is represented 

 by unity, — these vibrational numbers being the basis of what is 

 known as the natural harmonic series of musical intervals — 

 and this series being the same, whatever may be the absolute 

 pitch of the fundamental note or the character of tone of the 

 instrument. 



It is possible to make the lips give notes which, although 

 scarcely audible, are of definite pitch, without the use of an 

 instrument, just as a tuning-fork gives its proper note with or 

 without a resonator. 



There are two simple forms of resonators which give the 

 series of notes required in wind instruments : these are the 

 open tube of equal section throughout, and the cone complete 

 to its apex, where it is of course closed. In the tube the wave- 

 length of any note is inversely proportional to its vibrational 

 number; and the nodes or points of maximum compression 

 and rarefaction, and the centres of the ventral segments, or 

 points of maximum amplitude of vibration are equidistant: but 

 in the cone this is not the case. Wheatstone found experi- 

 mentally that the notes of a closed cone agree in pitch with 

 those of an open tube of the same length ; and therefore the 

 prime or fundamental tone of such a cone is an octave higher 

 than the prime of a closed tube of the same length. He found 

 also that in conic frustra of similar lengths, but of different pro- 

 portions as regards the diameters of their ends, the pitch varied, 

 rising as the difference between the two ends increased when the 

 small end was closed, and becoming lower under the same condi- 

 tions when the large end was closed. The accompanying dia- 

 gram (Plate I.) shows the positions of the nodes and centres 

 of ventral segments in an open tube and a cone of the same 

 length for the notes c, c 1 ', g f , c", marked 1, 2, 3, 4 (c having 

 128 vib., and a wave-length of 105 in. at 60° F.). The nume- 

 rals grouped together and marked N show the positions of the 



V. S 



nodal points or surfaces, and those marked — ~ — the centres 



of the ventral segments or points of maximum vibration. The 

 effect that the diminishing size of the cone has upon the posi- 

 tion of the nodes may be easily traced. Whilst the positions 

 of the centres of the ventral segments remain the same as in 

 the open tube (the numerals for these on the cone in the dia- 

 gram falling exactly under those for the open tube), the nodes 



