Jaitoabt 29, 1909] 



SCIENCE 



169 



varies as much as from a flute to a tin horn. 



One of the zinc pipes was placed inside 

 of a large pipe of zinc to form a double- 

 walled pipe, with spaces 2 em. wide between 

 the walls; the outer wall was attached to 

 the inner one only at the extreme bottom 

 on three sides, but just above the upper lip 

 plate on the front side. Attaching the 

 outer pipe did not alter the pitch or quality 

 in any noticeable degree. The double- 

 walled pipe gives a full fundamental tone, 

 F2 = 164, without conspicuous overtones. 



While the pipe is sounding continuously, 

 water, at room temperature, is allowed 

 slowly to run into the space between the 

 walls. As this space is filling, the tone of 

 the pipe changes conspicuously thirty or 

 forty times ; a few of these changes will be 

 noted. When the water is 5 em. above the 

 lower lip, the pitch rises by 2 vibrations 

 per second; when the water is 10 cm. high, 

 the fundamental tone breaks, and the first 

 overtone is clearly heard; at 11 cm. the 

 fundamental is almost inaudible, the first 

 overtone being loud; at 14 cm. the funda- 

 mental alone is heard, but with a pitch 6 

 vibrations sharper than at first. As the 

 water rises the pitch begins to fall, and 

 the overtone reappears, till, at a height of 

 water of 28 cm., the two tones are both 

 very distinctly heard, the fundamental 

 having a pitch of 164 Fj, the same as at 

 the beginning, and the overtone a pitch 2.13 

 times as great, about that of the tone FgS. 

 At a height of water of 29.5 cm. the over- 

 tone is heard alone, at 31.5 cm. the funda- 

 mental only is heard ; while at 33.5 em. the 

 two tones are mixed and are both clearly 

 sounded. These alternations are again re- 

 peated, and as the water rises to a height 

 of 46 cm. the fundamental begins to flatten, 

 till, at 57 cm., its pitch is 158, that of the 

 tone Eo, a semi-tone lower than at first. As 

 the pitch of the fundamental falls, that of 

 the overtone rises, and when the water 

 stands 69 cm. high, the fundamental has a 



pitch of 160, the overtone 400, the ratio is 

 2 : 5, or the tones, instead of being an octave 

 apart, are an octave and a third. The 

 actual sounds are Ej and G3S, and the two 

 sounds from the one pipe are each as clear 

 and distinct as the sounds from two sep- 

 arate pipes, as actual comparison has many 

 times proved to various observers. As the 

 water rises through the remaining 9 cm., 

 there are several changes in quality; when 

 the space is full of water the overtone, 

 though present, is less intense and is not in 

 such good tune. 



This pipe, which has the dimensions of a 

 wood pipe giving the tone G, has, when 

 empty, the pitch F, and when filled with 

 water the pitch is E ; during the filling the 

 pitch varies more than a semi-tone, first 

 rising and then falling, while the changes 

 in the quality of the tone are so astonishing 

 that they must be heard to be appreciated. 



The pipe has been filled with sand, and 

 it shows the same series of changes, though 

 some of the tones seem to be more deadened 

 than with the water filling, and it does not 

 seem to be quite so sensitive to slight varia- 

 tions. 



(Some photographic records of the varia- 

 tions in the sound waves coming from this 

 pipe, and the pipe itself will be exhibited 

 in another communication to the program 

 of this meeting. The photographs show 

 the distinctness of the changes that occur.) 



It is, of course, well known that the pitch 

 and even the quality of a pipe are influ- 

 enced by the thickness of wall and condi- 

 tion of the inner surface; but that the 

 properties of the pipe should be so pro- 

 foundly altered by even slight changes 

 entirely outside of the pipe was wholly 

 unexpected, even with a pipe of the con- 

 struction described. After the demonstra- 

 tion of these eifects, one will surely admit 

 that the quality of a wind-instrument may 

 be affected by the material of its body to 

 the comparatively limited extent claimed 



