and on Reed Organ-Pipes. 237 



to the upper surface of the block*. This is similar to the con- 

 struction of the Mundharmonicon, or Eolina, lately introduced 

 into this country from the continent, but it appears to have been 

 originally suggested by Dr. Robisonf. 



My first object being to verify Kempelen's account of the 

 vowels, I fitted one of my reeds R to the bottom of a funnel 

 shaped circular cavity open at top, of which Z, Fig. 5, is a section 

 (the pipe Tf"' standing on the wind-chest in the usual way) J, and 

 by imitating his directions for the positions of the hand within 

 the funnel, I obtained the vowels very distinctly §. I soon found 



* A section of Fig. 2, is seen in ils place at R, Fig. 11. In all the other figures R 

 is a section of Fig. 1. 



t Art. Musical Trumpet. Enc. Britt. Supplement to 3d ed. 1801. Works iv. 53S. 

 Wheatstone in Harmonicon, Feb. and Mar. 1839. 



X A reference to Fig. 13, in which a pipe is represented as standing on the wind-chest, 

 will serve to illustrate the subject to persons unacquainted with the structure of the organ, 

 and at the same time afford me an opportunity of defining certain technical terms which 

 1 shall be compelled to make use of. 



A large pair of bellows kept in motion by the foot, and so constructed as to afford 

 a constant pressure is connected with a long horizontal trunk, or wind-chest, of which kino 

 is a cross section, and which is therefore constantly filled with condensed air. The upper 

 side of this trunk consists of a very thick board pkql, which is pierced with a number 

 of passages similar to efg, every one of which is furnished with a valve or pallet kl 

 moving on a joint at k, and kept closed, by a spring m; a wire terminating in a knob 

 or key r, passes through a hole in the upper board, and rests on the pallet, so that 

 on pressing down this knob the pallet opens and a current of air immediately rushes 

 through the corresponding passage efg, and passes into any pipe AT which may be 

 placed over the aperture. In this instance R is the vibrating reed, to be set in motion 

 by the current. The term portevent is always used for that part of the tube TR which 

 lies between the reed and the wind-chest, and the term pipe for the portion BA, which 

 is between the reed and the open air, and it is to be understood that in all the figures 

 the lower end of the tube TF is supposed to be placed upon one of the holes of the 

 wind-chest. The pressure of the air is always measured by the number of inches of 

 water it will support in a common bent tube manometer; this is generally about 3 inches 

 in organs. 



§ I tliink it necessary to mention that the whole of the experiments described in this 

 paper were performed before the Philosophical Society on the same evenings that the paper 

 was read. 



