146 
Mon, 
Fig. 38 
Q, gauge; A, plasticine; B, oblique aperture, 
4/16 inch diameter, for equalizing internal 
and external pressure. 
Fig. 39 
Fig. 37, 
GF, GH and GJ gauges; A, rectangular steel body; 
B, two recesses, 1 1/2 inch diameter, .65 inch 
deep; C, cast steel plate, 1.496 inch diameter, 
1/8 inch thick, with central 3/8 inch hole; 
D, three jacketed coppers (as in Fig. 34) in each 
recess; E, brass spacing plate, with three 23/64 
inch holes on a 1 inch pitch circle for position- 
rs; F, 1/4 inch steel screw, diameter 
of head ish inch, for clamping the steel plate 
against the three coppers. foregoing digen- 
sions refer to the gauge, which is shown in the 
figure; the GH gauge is similar but has plates 5/8 
inch thick and recesses 1.15 inch deep; the GJ 
gauge has plates 3/8 inch thick, and a ring of 9 
coppers in each of the two recesses, which are .9 
inch deep. 
GZ gauge modified for measuring the pressure wave 
reflected from the sea-bottom; the figure is a 
view of the bottom of the modified gauge. 
