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1908.] Agents in the Oxidation of Amorphous Carbon. 245 
Measurement by means of the galvanometer of the E.M.F. produced by two 
thermo-elements at different temperatures, one placed in a sterile and the other 
in an inoculated flask, served to determine the difference of temperature 
between the two. | 
Diagram of Interior of Incubator. 
AA, Double-walled vacuum flasks. 
B, Thermopile, with terminals inserted in test-tube inside these flasks. 
, Jar packed with cotton-wool, containing junctions of thermopile wires D and 
galvanometer leads E. 
A thermopile with 20 junctions of the iron-nickel combination was 
employed and formed a highly sensitive instrument. The wires, silk-covered, 
32 gauge, had the junctions carefully brazed together and coated with shellac, 
and the wires themselves were enclosed in thin rubber to give protection 
against moisture. 
The mirror galvanometer used was of the Broca type with a resistance of 
50 ohms, and the electromotive force produced by a difference in temperature 
of 1/200° C. between the terminals registered a deflection of one scale- 
division. In an experiment of this nature, extreme precautions must be 
taken with all the junctions of different metals to avoid any thermal effects. 
To ensure that the junctions of the thermopile wires and leads to the 
alvanometer were maintained at the same temperature, these were connected 
with binding screws, insulated with thin rubber, and packed with cotton 
wool in a glass jar placed inside the incubator. The galvanometer leads 
passed through:a small perforation in the side of the incubator to a key 
of special construction and finally to the galvanometer. 
