803 
Sic 
(n) Results with two-ply gauge having steel foil eleotrodes, 
Typioal records are showm in Plate 4, Records 1a and 1b, 2a and 2b 
when the gauge was face-on (two opposite faces) and edge-on (two opposite 
edges) respectively to the pressure wave. The face-on records show double 
peaks with the second one larger than the first. The amplitude of the 
false peaks have been restored with the spring steel eleotrodes, with the 
restoration also of the spurious high frequencies. 
(0) Single crystal gauge with thiok stecl clootrodes. 
Thc construction remained standard except that the steel electrodes 
were inoreased to 0.25" thick. 
(p) Results with the single crystal gauge, having thick 
steel electrodes. 
Typical face-on and edge-on records are shown on Plate 4, Records 3 
and 4, Double peaks and increased oscillations appear, particularly in 
the fadc-on record. 
(q) Dwo-ply gauge with thick stecl cleotrodes. 
For the purpose of continuity, it appeared reasonable to re-construct 
the two-ply gauge with thick stoel outer clectrodes 0.25" thick and a 
central electrode 0.0015" thick. Otherwise, the construction remained 
standard. 
(r) Results with the two-ply pauge having thick steel electrodes. 
Records 1 and 2 on Plate 5, face-on and edge-on types respectively, 
show the pronounced frequencies set up by the thick steel electrodes and 
their masking effect on the true pulse. 
(s) Single crystal gauge with annealed copper electrodes. 
Annealed copper foils 0.022" thick were now cemented by gelva onto 
the faces of the crystal, but otherwise the construction remained unaltered. 
(+t) Results with single-ply gauge having copper electrodes. 
The face-on and edge-on signatures are shown on Plate 5, Records 3 
and 4, respectively. The face-on (second face not shown) did not show 
such a pronounced second peak and was quite similar to the pair of edge-on 
records. 
For the first time in this exploratory work with different thicknesses 
and materials of electrodes and insulation, the gauge was now arranged with 
its crystal faces parallel or perpendicular to the water surface and with 
the first few inches of the cable led horizontally away from the wave front. 
The pulses recorded are shown in Plate 5, Records 5 and 6. 
These two records are similar, and similar to the ones obtained 
(not shown) for the opposite faces and edges in the parallel and perpendicular 
directions with respect to the water surface. . 
But it is still to be noted that whilst the records are clcaner than 
those obtained with the stecl electrodes, they do exhibit markedly high 
frequency oscillations; morcover the steop wave front expected with the 
gauge facc-on is not in evidence. 
EXPERIMENTAL ...00 
