and on Reed Organ-Pipes. 261 



a little sharper than the reed, and its principal use appears to 

 be, that by its conical shape, it augments the loudness of the 

 note, on the principle of the speaking trumpet. But we have 

 seen, that although when the reed and pipe give the same note, 

 the undulations of the pipe disturb the motions of the reed, 

 whether the pipe be open or stopped at both ends, or stopped 

 at one end only; (always recollecting that the organ builder's 

 reed-pipe must be considered as stopped at the reed end), yet 

 that the amount of this disturbance varies Avith the place of 

 the reed in such a pipe, being greatest at the bottom of the pipe, 

 and least at its mouth*, so that it seems that the place hitherto 

 chosen for the reed is the worst possible, and that it ought 

 rather to be at the mouth of the pipe, in short that the best 

 arrangement would be that of Fig. 10, supposing the reed to 

 be at BD, and the pipe placed vertically. This too would give 

 the means of conveniently tuning the pi])e to the reed by the 

 plug PQ. With this arrangement the note of the reed is greatly 

 augmented, and its motions being undisturbed, it speaks more 

 readily. 



The other application of jjijjes to reeds has been in the vox- 

 humana stop, where very short pipes, not in unison with the 

 reed, are employed : the principles of this, however, have never 

 been thoroughly understood, and the whole has always been a 

 puzzle to the builders f. 



If by a voxhumana stop, we understand a stop possessing 

 the same vowel quality in every note, the thing is easily to be 



• See Note (D). 



+ According lo Biot, the pipes of the voxhumana are nearly of the same size, {Phys. II. 

 171 ■) but in the diapason given by B. de Celles, they differ considerably, although very 

 short {Facteur d'Orgues, pp. 84, 366). Their form is a cylinder set upon a truncated in- 

 verted cone, and half closed at the mouth. The length of cc = 9.lin. diameter 1.4 in. 

 length of c"'=3.3iu. diameter 1 in. 



