502 G. Barus — Application of the Displacement 



justable toward and from the rear, from right to left, and each 

 is revolvable about a horizontal axis normal to the figure, in a 

 way which will presently be shown. The distance between 

 pivots was 97 centimeters, the distance between the cylinders 

 AB and D about 111 centimeters, and the reduced end pro- 

 jects about 16 centimeters beyond the edge EE of the brick 

 pier to which the pivots are attached. D, clutched by C, is 



Fig. 1. 



the hollow stem of the tablet f, which holds the plane dot slot 

 arrangement to secure the grating g, a spring passing down the 

 interior of the tube D. . The lower pivot should preferably 

 point towards the center of gravity, G. 



The whole apparatus is enclosed in a more or less triangular 

 flat case h'mnk, firmly bolted to the wall at q, m and p. The 

 two sides of the case beyond the pier, h'ilk, may be slid off to 

 the left, and then the whole remainder lifted off its bearings 

 without touching the pendulum, as the case has no rear wall. 

 The front face is within three inches of the face of the pier. 

 This arrangement was found very satisfactory. The head of 

 the case ki is of course glass faced (identical plates) in front 

 and rear, so that the grating, etc., may be seen. A convex 

 mirror if placed at g reflects a beam of light showing the 

 pendulum to be nearly stationary daring the day, in spite of 



