44s Scripture — New Machine for Tracing Speech Curves. 



that the speech groove passes under a sapphire point which 

 follows the rise and fall in the bottom of the groove and moves 

 a light tracing lever. The point of this lever records the 

 movement on a long band of smoked paper passing over two 

 drums. The near drum is run by a belt directly from the 

 rotator. The speech curve appears in great magnification on 

 the band of smoked paper. When the band has gone once 

 around, the record is fixed by brushing the bach of it with an 

 alcoholic solution of shellac ; this fixes the smoke from the 

 back and produces a mat surface. 



The tracing lever is the critical part of the apparatus. Fig. 

 2 shows the end view of the rotator with the phonograph 

 cylinder. The sapphire at the end of a steel point follows the 

 rise and fall of the speech groove. The fulcrum of the lever 



Supporc 



Rubber Hinge 



Fig. 2. Tracing Mechanism. (Side view ; scale, 1:3.) 



to which it is attached is just to the left of it. The long arm 

 is made of two selected German straws of unusual lightness 

 and rigidity. This is balanced by a weight. The end of the 

 straw arm carries a somewhat modified Baylis point. This 

 consists of two small bits of cardboard united by a hinge of 

 the finest rubber membrane. One piece is attached to the 

 tracing lever, while the other carries a piece of light French 

 straw with a minute glass ball at the end. This form of record- 

 ing point gives a minimum of friction. 



Since there is no springiness in the rubber hinge the glass 

 point will not remain in contact with the paper. Springiness 

 was attempted by putting a fine hair across the hinge ; the 

 result was not satisfactory, as too light pressure would allow 

 the point to leave the drum when the speech curve deviated 

 from the vertical plane, and too heavy pressure diminished 

 the amplitude. By slightly tipping the hinge gravity could be 

 made to keep the point on the paper. Since it is impossible to 

 get the cylinder on the rotator so that the speech grooves lie 

 in absolutely vertical planes, some arrangement must be made 



