WRIGHT: ELECTRICAL GONIOMETER FURNACE 399 



cake Co, and serve to support the upper furnace part Ai, (figs. 

 1 and 2). Outside of these segments asbestos ring segments 

 are fitted as indicated in figure 3, d, e, f. Since alundum is a 

 good conductor of heat the alundum segments tend effectively 

 to render the heat distribution uniform at the center of the fur- 

 nace while the outside asbestos rings are poor conductors and 

 tend to confine the heat properly. In figure 1 asbestos wool 

 has been used in addition to the asbestos rings as an extra pre- 

 caution. The furnace opening at the crystal holder B is also 

 shielded to some extent by asbestos wool. 



Heat is supplied thru the wires, Fi, F^ (fig. 1), 4.5 to 5 am- 

 peres current at 110 volts being required to heat the furnace to 

 1150°. Cold water passing thi-u the tubes, Pi, P^, (fig. 1) and 

 and the water jackets, Ai, A^, completely protects the gonio- 

 meter parts from the heat. Temperatures are read by means of 

 the thennoelement {Ti, To, fig. 1) either on a millivoltmeter of 

 the Siemens and Halske type or on one of the potentiometer- 

 galvanometer systems of this laboratory. 



In order to adapt the two circled goniometer to such measure- 

 ments a special carriage (fig. 1,B) was made to replace the usual 

 crystal centering and adjusting carriage. This part is hollow 

 and into it a porcelain tube is inserted on the end of which small 

 platinum jaws are fitted, similar to those used in the themial 

 microscope recently described.^ In these jaws the crystal is 

 mounted and adjusted before the furnace parts are set in posi- 

 tion. Thiai the carriage B and the porcelain tube holder the 

 thermoelement wires (0.2 mm. in diameter and enclosed in fine 

 porcelain tubes) pass and are so adjusted that the bare ther- 

 mal junction of the thermoelement is in direct contact with the 

 crystal. 



After the crystal has been adjusted and centered approxi- 

 mately in the platinum jaws, the furnace part A2 is raised to 

 about the position indicated in figure 2. The alundum and as- 

 bestos ring segments are then put into position and the upper 

 furnace Aj placed on them. After the proper electric and water 



3 This Journal, 3 : 232-236. 1913. 



