and on Reed Organ-Pipes. 251 



corresponding points of each, but not in so great a degree. Tlie 

 whole amount by which the note is flattened varies, but is gene- 

 rally about a tone, it is accurately stated in the Tables*. 



The point n is by no means fixed, a jerk of the api)aratus, 

 a too hasty motion of the pipe, will make the reed leap Ijack to 

 the original note much sooner than it would do with a very 

 gentle and gradual motion ; it varies too with different reeds, 

 although their pitch be the same, and it varies with the pressure 

 of the bellows, the note changing sooner with a gi'eater pres- 

 sure. 



Now if we begin from any point beyond n, and shorten the 

 pipe gradually, its extremity may be brought considerably behind 

 n, (say to m) before it leaps back to the other note, so that in 

 fact at any point p between m and n there are two notes pq, pr, 

 which it may be made to produce, neither of them exactly its 

 proper one, but one a little flatter and the other a little sharper. 

 Some reeds upon fixing the extremity of the pipe between m 

 and n, may be made to change these notes from one to the other 

 by a dexterous jerk of the bellows upwards or downwards, and 

 to retain ' either of them for any length of time, at pleasure. 



With others again there is a point between in and n, where 

 the two notes appear actually to be heard at once, producing a 

 most singular effect. The real fact in this case seems to be that 

 the reed is producing its two notes alternately, but changing 

 quickly and periodically from one to the other, so that they seem 

 to be both going on at once. 



To produce these effects completely, a considerable pressure 

 of wind is sometimes requiredt. Should the reed be stiff", or the 

 pressure on it not sufficiently great, it becomes quite silent for 

 a considerable extent on both sides of p. 



• Vide Note A. t As much as six inches. 



II2 



