92 
ROBERT JAMES KELLOGG 
proves feasible for the diaphragm. The divergence of the 
paths RR' is increased by refraction or reflection, thus causing 
the ray or light-lever to describe on the screen P an enlarged 
representation of the vibratory movements of the diaphragm D, 
In form A (fig. 1 ), the paths RR' are made convergent by a 
lens of crossed glass or quartz fibers L2L3, whose proper radius 
of curvature (perhaps from 0.01 to 0.02 of an inch) must be 
experimentally determined. The paths RR' diverge again 
beyond the crossing point C, and when sufficiently far apart, 
have their rate of divergence increased by the concave lens L4 
(or by a convex glass-tube mirror, which can be made in the 
V 
Fig. 2. Principle of the Sonoscope, Form B (Horizontal Section) 
laboratory). The exact location of the various lenses must be 
such as to focus approximately the light-lever R on the screen 
P. The first focus of lens Li must fall between the diaphragm 
D and the fiber lens L2L3; the second focus P2 of the lens L2L3 
will fall beyond the crossing point C, because divergence within 
the ray before reaching the fiber lens L2P3 is greater than that 
between its paths RR', The concave lens (or convex mirror) 
L4 must be placed between the crossing point C and the second 
focus F2, thus prolonging the focus to P3 on the film or screen P. 
In form B (fig. 2), a convex glass-tube mirror M replaces the 
lenses L2L3 and Li of form A. The first focus Pi must fall be- 
