Vol. 8, 1922 
PHYSICS: C. BARUS 
165 
hole O, figure 7, the pipe h beyond being the rubber connection to the 
[/-gauge. The negative pinhole resonator runs down in sensitiveness much 
more rapidly (if treated in this way, pinhole remote), than if the pinhole 
is fixed in the bottom of the resonator, and a connector h of any length, 
communicates with the [/-gauge. 
Positive and Negative Pinhole Resonators Cooperating. — It is obvious that 
the positive (pinhole cone O salient) and negative (pinhole cone 0' re- 
entrant) pinhole resonators, R and R\ figure 8, must add their respective 
pressure effects at the gauge U U', if they are provided with independent 
connector tubes t and f . A large number of such experiments all indicated 
that the separate deflections may be added, at least very nearly. The 
sensitiveness may thus be nearly doubled. It is probable moreover that 
two resonators will interfere less with each other than two positive or two 
negative resonators (i.e., two identical resonators, generally), if placed a 
short distance apart. The deflection in fact, falls off slowly and does not 
quite vanish even with a mere crevice between the mouths. If the two 
resonators are parallel, side by side and mouth near mouth, the conditions 
are even better. Hence if R R' , figure 8, are placed side by side, and the 
connector tubes t, t' are of pure rubber, elongated if necessary, the twin 
apparatus is available for exploration. 
With short connectors t f m the interest of greater sensitiveness, I 
made a number of tests to find the maximum distance for which the twin 
resonators (fig. 8) would respond. They were able to hear an organ pipe 
to a distance of 6 meters, the deflection being then about a fringe. 
Although a single resonator with a branched tube is ineffective, the 
suggestion of using the bottom of the resonator R figure 9, as a branch point 
for the connector tubes t t' to the gauge U U', seems highly promising. 
One and the same resonator here functions in both (positive and negative) 
capacities. The design succeeded with, as it seemed, but little sacrifice 
of sensitivity. Figure 10 shows the fringe deflections 5, obtained along 
y, for the case of short connector tubes t t' (30 cm. long), with the pipe 
(at X = bO, y = 40, z = 50 cm.), near the center of the table. In figure 
11 the same result is extended with long connector tubes {t = 130 cm.). 
In curve 12 finally, the results refer to a more distant pipe Sitx= 100 cm., 
y = 40, z = 50 cm. All curves fall off quite abruptly at the two edges 
of the table y = — 27 and + 93 cm. The extreme importance of tun- 
ing was noteworthy throughout; mild notes frequently giving large de- 
flections, sometimes out of field, whereas strong notes pf the same pitch to 
the ear dropped the fringes back to zero. A variety of experiments were 
made with this =i= resonator with results like the above which need not 
therefore be reported. 
* Advance note from a Report to the Carnegie Institution of Washington, D. C. 
