C. T. Knipp — New Form of Make and Break. 283 



Art. XXX YI. — A New Form of Make and Break; by 



Charles T. Knipp. 



A make and break to operate a sounder so as to tick seconds 

 is indispensable in a well-equipped physical laboratory. The 

 method of allowing a tip of platinum wire, fastened to the 

 lower end of the second's pendulum, brush through a drop of 

 mercury on an amalgamed brass or copper support, is vexing 

 in the extreme and not in the least reliable. It requires con- 

 stant attention, as the mercury is readily oxidized by the mak- 

 ing and breaking of the current. 



The following device is easily made and can be readily 

 attached to any second's pendulum. The general arrangement 

 is at once seen by aid of the figures. 



I 



h 



Fig. 1. The T, a c e is pivoted at k; s, s are delicate springs made of sheet 

 steel. Adjustments are made by means of the thumb screws t, t and the set 

 screws r, r. The current is connected through the binding posts b, b. The 

 pendulum MN' carries a stud which engages the lower end of the T, a c e. 



Fig. 2. Shows a side elevation and manner of pivoting at k. 



The T-shaped frame is made of thin sheet brass. It is 

 pivoted at the center. At the lower end of the stem of the T 

 is a slot which engages a stud on the pendulum. Fastened to 

 the ends of the arms are short arms which project downward. 

 At the lower end of each small arm is soldered a platinum tip. 

 Clamped at one end of a brass frame, supported by a thumb 

 screw, is a delicate spring of sheet steel. The spring is held 

 in the desired position by a set-screw at the other end of the 

 frame, as shown in the left hand side of fig. 1. The adjust- 

 ment should be such that when the pendulum is in its lowest 

 position the platinum tips just touch the springs. The adjust- 



