THB CALORIMETER SYSTEM AND MEASUREMENT OF HEAT. 143 



No. i may be read at once, the outer connecting wires which take in all 

 the junctions in system No. i are carried to the mercury cups beneath 

 the key designated A L, L, No. i . As is seen on page 1 16, this deflection 

 corresponds to the average temperature difference between the zinc and 

 copper wall. In the same way the algebraic sum of the deflections of 

 the four parts of No. 3 system can be read directly by depressing the 

 key designated as A L, I, No. 3. 



The key designated as No. 2 controls the connecting wires from the 

 ventilating air-circuit, and by depressing this key the temperature dif- 

 ferences between the ingoing and outcoming air are noted directly, not 

 as absolute temperature measurements, but rather as an indication of 

 the necessity for warming or cooling the entering air to adjust its tem- 

 perature to that of the air leaving the calorimeter chamber. 



It is thus seen that eight keys control the temperature indications of 

 the sections of the thermal junction circuits, and that three keys indi- 

 cate temperature conditions respectively in the whole of system No. i , 

 the whole of system No. 3, and the air current. For the indication of 

 these temperature conditions, therefore, eleven keys are employed. 



The connections shown by the wires in figure 42 can be followed 

 more exactly by the plan of wiring given in figure 43. This diagram 

 can be compared advantageously with the view of the switch given at 

 the left in figure 40, as the diagrammatic features of the plan of wiring 

 are made to correspond very closely with the exact location of the dif- 

 ferent parts of the switch proper. For example, the two coils wound 

 on hard-rubber spools and fastened to the switch by screws through the 

 center of the spool, which are shown in figure 40 at the top, correspond 

 to the two coils marked 2o-ohm res. on the diagram. The two iron 

 cups which are filled with mercury when the switch is in use, and in 

 which the galvanometer terminals are immersed, are between these two 

 coils, while the iron post from which wires pass to each of the 2o-ohm 

 coils is between the galvanometer connections, exactly in the middle of 

 the upper portion of the switch. The two wires leading from the gal- 

 vanometer can readily be traced on figure 43 to these two iron cups. 

 It can be seen further that one of the wires from the battery connects 

 directly with the iron post between the galvanometer cups, which corre- 

 sponds to point B' in figure 44 beyond. 



On each side of the circle designating the galvanometer is placed a 

 diagram of a thermal junction system, that corresponding to the inner 

 metal- wall system, i. e., No. i, on the left, and that corresponding to 

 the outer system, i. <?., No. 3, on the right. Furthermore, the connec- 

 tions of the separate sections, T, U, L, B, are shown for each system. 

 Immediately above system No. i is the representation of system No. 2, 



