620 RECORDS. 



P. H. Dudley, Translative Curves of Counter Balance 

 AND Crank Pins in Running Locomotive. 



In the absence of the Secretary, Mr. Theodore G. White was 

 elected Secretary pro tcin. 



The principle illustrated in Professor Hallock's paper may be 

 stated as follows : Any system that has an inherent rate of 

 vibration in itself, will respond to vibrations of the same period 

 as its inherent vibration factor, but is indifferent to vibrations 

 faster or slower than that particular rate of inherent vibration. 

 The model consists of a brass ring, on the center of which a 

 brass ball is held in equilibrium by means of three spiral springs 

 which are attached to points equi-distant from one another around 

 the circumference of the ball, and at their other extremities to 

 points equi-distaht from one another, upon the inner circumfer- 

 ence of the ring. The model is suspended from the axis per- 

 pendicular to the plane of the ring and springs. Vibrations are 

 imparted to the model thus suspended, by means of a string, or 

 better, by means of a spiral of wire, attached to the ring, and 

 held by the hand in a horizontal po.sition. Vibrations delivered 

 through the weak spiral spring, impart a succession of impulses 

 to the ring, while the ball has its ow^n inherent rate of vibration 

 in the plane of the ring itself, due to its mode of suspension. 

 When the vibrations imparted to the ring are too rapid or too 

 slow, beats are produced, which disappear as the rapidity of the 

 induced vibrations approaches the inherent rate of vibration. A 

 modified form of the same apparatus consists in suspending the 

 former apparatus concentrically within a second brass ring, so as 

 to connect the two rings. One rate of impulses is then imparted 

 to the outer ring, and b}^ means of the spirals connecting the 

 concentric rings, another set of impulses is imparted to the second 

 ring, according to their inherent rates of vibration. 



In the discussion of this paper. Professor D. W. Hering sug- 

 gested connecting the string or spiral by which impulses are im- 

 parted to the ring, to a tuning fork, the rate of vibration of which 

 could be regulated by weighting and which could be operated 

 electrically for reciprocating motion of small amplitude and of a 

 known rate. 



