THE CALORIMETER. 33 



ing experiments is that of the thermo-electric effect of the thermal junction 

 systems installed on the calorimeters. To aid in indicating what parts of 

 the zinc wall need cooling or heating, the thermal junction systems are, as 

 has already been described, separated into four sections on the chair calo- 

 rimeter and three sections on the bed calorimeter ; in the first calorimeter, 

 the top, front, rear, and bottom; in the bed calorimeter, the top, sides, and 

 bottom. 



CONNECTIONS TO THERMAL-JUNCTION SYSTEMS. 



Since heretofore it has been deemed unwise to attempt to use both calo- 

 rimeters at the same time, the electrical connections are so made that, by 

 means of electrical switches, either calorimeter can be connected to the 

 apparatus on the table. 



The thermal-junction measurements axe made by a semicircular switch 

 S 7 . The various points, i, n, in, iv, etc., are connected with the different 

 thermal-junction systems. Thus, by following the wiring diagram, it can 

 be seen that the connections with i run to the different binding-posts of the 

 switch S ]0 , which as a matter of fact is placed beneath the table. This 

 switch S 10 has three rows of binding-posts. The center row connects di- 

 rectly with the apparatus on the observer's table, the outer rows connect 

 with either the chair calorimeter or the bed calorimeter. The points marked 

 a, b, d, e, f, etc., connect with the bed calorimeter and A, B, D, etc., connect 

 with the chair calorimeter. Thus, by connecting the points g and i with 

 the two binding-posts opposite them on the switch S 10 , it can be seen that 

 this connection leads directly to the point I on the switch S 7 , and as a 

 matter of fact this gives direct connection with the galvanometer through 

 the key on S 7 , thus connecting the thermal-junction system on one section 

 of the bed calorimeter between g and i directly with the galvanometer. 

 Similar connections from the other points can readily be followed from 

 the diagram. The points on the switch S 7 indicated as i, n, in, iv, cor- 

 respond respectively to the thermal-junction systems on the top, rear, front, 

 and bottom of the chair calorimeter. 



By following the wiring diagram of the point v, it will be seen that this 

 will include the connections with the thermal junctions connected in series 

 and thus give a sum total of the electromotive forces in the thermal junc- 

 tions. The point vi is connected with the thermal-junction system in the 

 air system, indicating the differences in temperature between the ingoing 

 and outgoing air. It will be noted that there are four sections in the chair 

 calorimeter, while in the bed calorimeter there are but three, and hence a 

 special switch S 8 is installed to insure proper connections when the bed 

 calorimeter is in use. 



This system of connecting the thermal junctions in different sections to 

 the galvanometer ma.kes possible a more accurate control of the tempera- 



