and on Reed Organ-Pipes. 259 



which in the former experiments were found to occur only at 

 odd multiples of the half length. In this case, one portion of 

 the pulses generated by the reed, is propelled past the sides of 

 the piston to the mouth of the pipe, and thence echoed back- 

 wards and forwards between B and N, producing the vowels, 

 and the remaining portion echoed between M and P, as if PM 

 were a pipe stopped at both ends, in which case we have seen 

 that the secondary pulses unite, and therefore disturb the motion 

 of the reed, when the pipe equals the whole wave, or a multiple 

 of it. 



If the reed R, instead of being inserted into the piston as in 

 Fig. 6, be fixed to the end of a slender tube IVR, (Fig. 9), which 

 slides air-tight through a collar of leather attached to the piston, 

 so that the length PS admits of alteration at pleasure, the vowels 

 and other phenomena are still found to depend upon the length 

 PB, (all those of course that would have been produced from 

 P to S being lost.) 



If the reed be attached to the end of a portevent TFR, 

 (Fig. 10), and presented to the tube ABCD, which is provided 

 with a solid piston PQ, the vowels and other phenomena are 

 still produced as before, and still depend upon the actual length 

 PB of the greater tube. 



There is one curious circumstance about the two last experi- 

 ments, that although the flattening takes place only when PB, 

 (Figs. 9, and 10.) is equal to the half wave of the reed, or some 

 odd multiple of it, the amount of it varies with the distance of 

 the reed from the mouth of the tube; being greatest, when BS 

 is the half wave, or an odd multiple of it, and almost imper- 

 ceptible, when BS is the whole wave, or a multiple, or when 

 BS vanishes, that is, when the reed is exactly at the mouth of 

 the pipe*. This appears to depend upon the different variation 



See Note (D). 

 KK 2 



