ACOUSTICS AND GRAVITATION. 



29 



A survey of the fringe displacement corresponding to different harmonics is 

 given in figure 39, when 1,000 ohms completed the telephone circuit. Their 

 distribution is less regular than heretofore. If we place them a semitone below 

 d' , a', a", the one between a' and a" is missing. What particularly astonishes 

 is the occurrence of resonance at these relatively low notes, seeing that the 

 resonator volume is here nearly negligible. The maximum displacement of 100 

 fringes corresponds to a pressure increment of about 0.03 cm. of mercury, 

 which, though twice as large as obtained with the large resonator ///, is never- 

 theless of the same order of values. A variety of other experiments made with 

 different nozzles attached to this cup-shaped cylindrical shell were not quite 

 consistent as to the location and number of overtones. 



d 1 e f a 1 a' c"a" e r " a 



-/aw 



T * i --T-. -_i i ' ' L t f - 



3" d & d & g, a c' d' e' gf a' e" d" e' 



2' a at & cf e? a' a" 



o u 



Thus figure 40, obtained with a conical vent (somewhat too large here), 

 shows but two maxima near g' and g", the others being obliterated or very 

 low. A fine pin-hole 0.03 cm. in diameter in copper foil was therefore prepared 

 and tested on the modified motor break, between A and a", with results given 

 in figure 41. The figure shows much greater detail, there being maxima near 

 a, a 1 , a", e, e f , e" Yet this is not the whole list, for the curve is probably much 

 more closly serrated. The smaller indentations are slurred over by the imper- 

 fections of the subjective method of observation. A special search made for 

 maxima brought such locations as M, for instance. 



In one respect the present curve, figure 41, for the shell resonator IV 

 differs conspicuously from the curve, figure 38, for the capacious resonator ///. 

 In the latter, conformably with the large volume, the lower notes (8-foot 

 octave) are very much more effective than the notes of the i-foot octave. 

 The curve as a whole falls from left to right. In figure 41 the reverse is ob- 

 served. In fact, it is rather surprising that for the case of the very small 



