THE RESONANT RECORDER 19 



afterwards easy to reproduce this record by contact-print 

 on a photographic paper. 



Adjustment of the Writer 



It is sometimes necessary to have the recording-point 

 brought two or more times to the same place, in order 

 that the successive records may be rendered the more 

 strictly comparable. This is accomplished by a rack and 

 pinion to adjust the height of the platform carrying the 

 plant. When the platform is lowered, the petiole, which 

 is attached to one arm of the recording-lever, pulls it down, 

 and the recording-point is moved to the left. When the 

 platform is raised, then by the action of the counterpoise 

 attached to the other arm of the lever the index is moved 

 in the opposite direction. In this way the recording-point 

 can be brought to any position that is desired. The same 

 end is secured through adjustments of a micrometer by 

 which the carrier of the writing-index is raised or lowered. 



Another adjustment that is necessary is the bringing 

 of the recording-point near to the writing-surface without 

 actual contact ; so that, when the index is set in a state 

 of resonance, it may trace a dotted Hne. The necessary 

 adjustment is brought about by means of a micrometer-screw 

 at the top of the instrument, by which the lever can be made 

 to approach or recede from the writing-surface. When the 

 speed of the plate is slow, the successive dots may be so 

 close together as to appear hke a continuous Hne. 



More troublesome is the adjustment necessary to render 

 the plane of movement of the index exactly parallel to the 

 writing-surface. If this be omitted, the writing-point in 

 one part of the record, say to the right, will be too far 

 away to strike the surface, whereas in another part, say 

 to the left, it will press against the plate and lose its freedom. 

 This difficulty I have been able to overcome by mounting 

 the vertical rod, carrying the writer, inside another tube. An 

 attached tangent-screw, t, then causes a very slow rotation 



c 2 



