THE CALORIMETER. 



41 



The bar is in contact with the slide-wire J and therefore varies the position 

 of the point q and it also carries with it a stylographic pen. The movements 

 of this bar to the right or the left are produced by an auxiliary electric 

 current, the contact of which is made by a plunger-plate forcing the pointer 

 P against either S t or S 2 . P makes the contact between PI and either S t 

 or S, and sends a current through, solen- 

 oids at either the right or the left of the 

 creeper. At intervals of every 2 seconds 

 the plunger rises and forces the pointer P 

 against either S x , ft, or S 2 above. The 

 movement of this plunger is controlled by 

 a current from a 110- volt circuit, the con- 

 nections of which are shown in fig. 22. If 

 the contact is made at T, the current 

 passes through 2,600 ohms, directly across 

 the 110- volt circuit, and consequently 

 there is no effective current flowing 

 through the plunger PI. When the con- 

 tact T is open, the current flows through the plunger in series with 2,600 

 ohms resistance. T is opened automatically at intervals of 2 seconds by the 

 clock. 



The movement of the contact arm along the threaded rod is produced 

 by the action of either one of two solenoids, each of which has a core at- 

 tached to a rack and pinion at either end of the rod. If the current is 



passed through the contact S t , 



Fig. 21. — Diagram of wiring 

 actuating plunger and creeper. 



1 



IIO v 



600^ 



ooo °[^vvw\/ l M/ww l i 



L-^V^- 350^. 350 A -WV -1 

 IOQOO A 



L wm 



a current passes through the 

 left-hand solenoid, the core 

 moves down, the rack on the 

 core moves the pinion on the 

 rod through a definite fraction 

 of a complete revolution and 

 this movement forces the 

 creeper in one direction. Con- 

 versely, the passing of the cur- 

 rent through the solenoid at 

 the other end of the threaded 

 rod moves the creeper in the other direction. The distance which the iron 

 rack on the end of the core is moved is determined carefully, so that the 

 threaded rod is turned for each contact exactly the same fraction of a revolu- 

 tion. For actuating these solenoids, the 110-volt circuit is again used. The 

 wire connections are shown in part in fig. 21, in which it is seen that the 

 current passes through the plunger-contact and through the pointer P to 

 the silver plate S x and then along the line G x throusrh 350 ohms wound 

 4 



Fig. 22. — Diagram of wiring of complete 110-volt circuit. 



