Reed pipes are made to speak by an apparatus very different from what we have described. Fig. I. Plate CCCCXLVI. a a, b b, is a brass cylindrical, or rather slightly conical, tube, b b being the widest end, having a longitudinal narrow opening in the front. The end b b is cut slanting upwards and backwards, and is closed by a piece soldered on it. The tongue a c is a thin plate of metal, which lies upon the longitudinal opening of the reed, firmly kept to the reed at its upper end a, licit free at the lower end, and slightly curved away from the reed. This apparatus is firmly fixed in a solid block d, Fig. 5. the open end of the reed passing through it. The tuning spring e e e, 5. and 7. is a piece of wire which passes through the block, and, bending up to wards the top of the tongue, presses firmly against it, keeping it close to the reed, and, by being pushed down or drawn up, shortens or lengthens the free part of the tongue, for the purpose of tuning. The foot, or socket A, Fig. 6. is a cone in which the lower part of the block, with the reed, tongue, and tuning spring, are in closed, and is quite closed by the block at its large end, but open at the apex f to receive the wind. The tube, properly so called, is of various shapes, B, Fig. 4, 5, 6, 11, 12. This tube gives the quality of the tone, and makes the difference between the different kinds of reed pipes. Fig. 5. and 6. is the trumpet ; Fig. 11. the oboe ; Fig. 12. the cromorna, vulgarly called the cremona ; Fig. 4. the vox humana ; which last produces a quality of tone resembling the hutnan voice, but generally of very poor effect. The tube of the bassoon is a Ion.- narrow cone, Fig. 19. the quality of which is much thinner and less powerful than the trumpet.
1Vhen the pipe is set in its place, thc wind fills the socket, and presses the tongue against the reed, shutting the lonitudinal opening : the elasticity of the tongue im mediately carries it farther off than its position at rest ; it is again forced against the opening, and again recedes; and thus, by its vibrations, gives the note which the pipe is to speak. As the tongue, by means of the tuning
spring, is lengthened or shortened, its vibrations are slower or quicker, and the note, of consequence, lower or higher.
The goodness of a reed-pipe depends on several cir cumstances : 1st, The composition of the metal of which the tongue is made. Sonie organ-builders use common brass, others a composition with a larger proportion of copper. 2d, The thickness of the plate of which the tongue is made, which varies according to the weight on the bellows, or loudness to which the stop is to be voiced , a chamber organ requires much thinner tongues in the reed stops than church organs. 2d, The curva ture of the tongue, or the quantity of the opening be tween it and the reed : the more open it is, the louder, but generally, on that account, slower to speak. 4th, The smoothness and flatness of the edges of the aper ture in the reed over which the tongue lies.
Biot, in his Traice de Physique, gives an account of some improvements made at Paris on reeds, and as they seem of great importance, we shall give a transla tion of the passage.
" I have been describing reeds such as are ordinarily used ; but I am very happy in having it in my power to add to these notions the account of several remarkable improvements introduced into their construction by M. Grenie, an able amateur of music, who, by means of a modification equally simple and ingenious, has succeed ed in removing their former faults, and in giving them new qualities.
" Greni makes the reed AR, Fig. 2. Plate