Il6 A RESPIRATION CALORIMETER. 



Electrical connections of the elements. As may be seen from the illus- 

 trations in figures 25, 29, and 30, all the elements are connected in 

 series. When the ends of the whole system are connected with the 

 galvanometer the deflection obtained is not that due to the current 

 from a single element, but it is the resultant of all the positive and 

 negative electro- motive forces of all the elements. It is very essential, 

 however, to be able to determine temperature conditions for different 

 sections of the total area of the chamber. It is conceivable, for ex- 

 ample, that even while the zinc and copper walls at the ends and sides 

 of the calorimeter remain adiabatic, at the top the zinc wall may be 

 warmer than the copper, and at the bottom the copper wall may be 

 warmer than the zinc. If there were the same difference in tempera- 

 ture in both cases the algebraic sum of the electro-motive forces would 

 be zero, indicating that the temperatures of the zinc and copper walls 

 were the same over the whole area, and consequently no passage of 

 heat in either direction, whereas heat would actually be passing out 

 at the bottom and entering at the top. 



In order to prevent such temperature differences in local sections of 

 the total area, the whole system of elements is subdivided into groups 

 corresponding with different regions, so that it is possible to detect not 

 only average temperature differences for the total area, but also local 

 differences. The whole surface area is divided into four parts, the top 

 being one and the bottom another. The upper double row of elements 

 connected by wires in a zigzag line comprises the third division, and 

 the lower zigzag row and the row in a straight line around the bottom 

 together form the fourth division. For convenience these divisions 

 are designated as top, bottom, upper zone, and lower zone, respectively. 

 By means of connecting wires leading from the points at which the 

 various sections are joined together, each individual section can be 

 connected at will with the galvanometer and the temperature differ- 

 ences indicated by the electro-motive force ascertained. 



It will be seen by comparing the above explanation with figure 29 

 that the division of the vertical walls of the calorimeter in the two zones 

 is not an equal one, the upper zone being much less in area than the 

 bottom. Since, however, the upper zone is subject to much wider 

 fluctuations in temperature because of variations in the temperature 

 and exposed surface of the heat-absorbing system, it is advisable to 

 have temperature differences located in this small zone as precisely as 

 possible. 



While the thermal junctions in each group are used to detect tem- 

 perature differences between the copper and zinc walls, no absolute 

 measurements of such differences are made. In general, the differences 



