E.. W. Biake, Jr.— Articulate Vibrations. 55 
record of the combined motions. Dr. Stein considers his 
method applicable to vocal sounds, but I cannot learn that he 
has ever attempted this application. My own Sei Sa a in 
that direction by Stein’s method resulted in failu 
The object of this paper is to describe a method of obtain- 
ing photographs of minute vibrations on a magnified scale. 
plane mirror of steel, A, is supported by its axis in the 
metal frame B. The ends of the axis are conical, and carefully 
fitted into sockets in the ends of the screws C, C. On the back 
of the mirror is a slight projection D pierced by a small hole. 
The vibrating disc, as hitherto employed, is a circular plate 
of ferrotype iron, 23 inches in yeti screwed to the back of 
a telephone mouth-piece of the for 
invented by Professor John Petes: 
and now universally used. From O 
the center of the back of this disc a fi 
stiff steel wire projects, the end of ¢ 
which is bent ata right angle. This 
care | patties Canduler to re eens dias 
de a beam of sunlight Soripecbeigs through a 
small crear opening. This beam passes intoa dark closet 
45° to the | horizon. The ra 
pass through a lens at whee! focus bin! form an intensely lumin- 
ous sponds of the circular openin 
carriage moving smoothly on four wheels travels beneath 
the lens at such a distance that the sensitized plate laid upon it 
comes at the focus for actinic rays. A uniform velocity is given 
to the carriage by a string fastened to it and passing over a 
Prictis “To this string a lead Shee bs sufficient to balance 
The velocity attain = e carriage is det paaaners by p 
ing a sheet of smoked glass upon it and letting it ran under 
