492 



SCIENCE 



[N. S. Vol. LIII. No. 1378 



is long retained whether the current is there- 

 after broken or not. It is gradually dissi- 

 pated, however, as the joint at the telephone 

 plate is rarely quite tight; and when the tele- 



of pitch upon the dilatation of the closed 

 resonator B. An electric siren (§8) was here 

 used with 2,000 ohms in the telephoae circuit. 

 The results appeared about as follows: 



g' to 6' C" d" to e" 



— 5 — 25 maximuin estimated at - 



/" g" pitch 

 -200 — 35 fringes 



phone sounds, iwessure increments may even 

 become negative, as above. If most of the 

 water is removed by bibulous paper a mod- 

 erate fairly constant pressure is usually ob- 

 served for some time, until (doubtless with the 

 breaking of the film across the hole) the may- 

 imnTn is suddenly again attained. 



7. Inside and Outside Stimulation. — When 

 the tube c' is inserted within the rubber con- 

 nectors t, t' in the absence of vents, there is 

 much undesirable pressure disturbance at the 

 outset, which is but very slowly dissipated. 

 Moreover the closed space can not be opened 

 again at pleasure without similar commotion. 

 I, therefore, used the apparatus. Fig. 6, in 

 preference, in which the pinhole tube c' is 

 provided with a branch tube t" and cock C. 

 The rubber tube t leads to the telephone (be- 

 yond T) and the tube t' to the mercury U-tube 

 (beyond Z7). If C is open, c' may be inserted 

 or withdrawn with facility. If C is closed 

 the resonator B is closed, as in the above case. 



Using the mercury interruptor (frequency 

 c) with 2,000 ohms in circuit the deflection 

 of the closed region was invariably negative. 

 The deflection is peculiar, moreover, inasmuch 

 as it is a slow growth within a minute or 

 more, to a maximum. On breaking the cur- 

 rent the deflection dies off in the same slow 

 fluctuating way. If the cock C is opened, 

 the zero is instantaneously recovered. In 

 other words the dilation is due to a loss of gas 

 within the closed region, which loss is but 

 slowly restored after the telephone ceases to 

 vibrate. 



If the cock C, Fig. 2, is opened at the 

 critical point, or if it is replaced by the tube c, 

 the deflection is again iwsitive. The action 

 of c thus exceeds that of c, probably because 

 the pinhole in c happens to be nearer the 

 critical size than in c. 



The question next at issue is the influence 



There is thus an enormous maximum dila- 

 tation somewhere in the range of frequency 

 d", e" , which from the hovering character of 

 the deflection is not further determinable. 

 This amounts to a pressure decrement of 

 Ap = — 6 X 10"^ cm. of mercury with 2,000 

 ohms in the telephone circuit. At 100 ohms 

 it would have been about a millimeter of 

 mercury. 



The slow growth of relatively enormous 

 pressure decrements here recorded is so sur- 

 prising that further experiments are needed. 

 To begin with one may ask whether the tele- 

 phone plate, held as usual by strong screw 

 pressure between annular plates of hard rub- 

 ber, is adequately airtight. I therefore re- 

 moved the telephone and sealed all these 

 parts with cement, thoroughly. 



On replacing the telephone with the adjust- 

 ment as in Fig. 6, the behavior had in fact 

 changed, the negative pressure being of the 

 small value indicated in §2, without growth 

 in the lapse of time. In other words the 

 presence of the pinhole c' within the closed 

 region was now ineffective. 



We may summarize these early results for 

 the particular frequencies used, as in Figs. 9 

 and 10. In an air region B, closed on one 

 side by a vibrating telephone plate T and on 

 the other by a quiet plate TJ , the pressures are 

 distributed as if there is a maximum at T and 

 a minimimi at TJ . If the region B, Fig. 9, com- 

 municates with the atmosphere by a pinhole 

 of the critical diameter, the pressure within B 

 is raised as a whole by the amount which the 

 pinhole air valve will withstand. Again if 

 the closed region T TJ , Fig. 10, contains a pin- 

 hole valve within only, it does not differ 

 essentially from the corresponding case in 

 Fig. 9; but if an additional very fine leak 0' 

 is supplied on the T side. Fig. 10, the TJ side 

 gradually develops a large pressure decre- 



