180 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



tacts were thus closed and in proper position before the offset picked 

 up the arm of the eccentric at the beginning of its second revolution. 

 The wheel W was driven from a variable-speed, worm-gear motor M, 

 which was arranged to run silently. The contact S had a permanent 

 mounting. >S' was mounted on a metal disk Z>. This also carried a 

 scale giving degrees, and moved about the axis of the stud T. It was 

 kept in position and could be clamped by the lugs L and L and moved 

 conveniently by the handle H. The position of this movable disk 

 determined the distance between the contacts S and S', and thus the 

 duration of the electric shock. A hard block of insulating material /, 

 mounted on the arm A, provided against electrical connections between 

 the two contacts when the pen- 

 dulum should swing past them. A 

 pointer at P, secured to the arc K, 

 indicated the degrees of separation 

 between the switches. 



The essential detail of one of the 

 contacts opened by the moving pen- 

 dulum is made clear in figure 45, 

 which is a drawing of the back of S 

 in figure 44. The block of rubber 

 R, about which the contact device 

 is built, is 33 nun. square and 26 

 mm. thick (vertical direction in the 

 figure). In mounting it is secured 

 to a metal plate m by posts and nuts 

 n and n'. The two parts of the 

 contact, a and b, are shown at the 

 left. Only the binding-post for b 

 is visible in the drawing; this is at 

 the extreme right, a, the movable 

 part which is struck back by the 

 arm of the pendulum is held in 

 metal supports at x and y. Good 

 electrical connection with this moving portion is assured by the spring 

 I, which also normally serves to hold the contact surface of a against 

 that of b. A steel spring s is so located and held in definite position by 

 pointed screws, which press into appropriate openings at one end, that 

 when a is moved forward by the pendulum it can not return into con- 

 tact with b, as would naturally be caused by the spring I, since a is 

 caught on the detent d of the spring s in the position shown in the 

 figure. It is retained here out of contact with b until the foot / passes 

 over the plunger p, depressing the spring s and releasing a, so that it 

 reestabUshes good contact with b. The apparatus is arranged so that 

 the contact between a and b is made in the switch S some time 



Fig. 45. — Detail for one of the contact de- 

 vices struck open by the pendulum. 



R, rubber block 33 mm. square and 26 mm. 

 thick ; m, metal base for securing block 

 by posts and nuts, n and n' ; b, fixed part 

 of contact; o, movable portion of contact 

 fastened in metal parts, a; and y; s, spring 

 with detent, d, to catch and hold o after 

 it is struck back from b by pendulum; 

 /, a foot which depresses plunger, p, 

 which in turn depresses d, allowing o 

 under the impulse of the spring I to re- 

 turn into contact with b ready for the 

 next pendulum stroke. 



