298 Mr. Carl Bams on the Fusion 



The charged crucible is shown at K (figs. 1, 2, and 3), and 

 is held in position by two crutch-shaped radial arms, $,N, of 

 fire-clay, the cylindrical shafts of which fit the iron tubes 

 P, P, snugly, and are actuated by two screws, R, R. More- 

 over P, P are covered with asbestos (not shown), and thus 

 subserve the purpose of handles, by grasping which the two 

 halves of the furnace may be rapidly jerked apart. It is by 

 this means that the crucible is suddenly dropped out of the 

 furnace into the calorimeter immediately below (not shown). 

 Care must be taken to have the arms N, N free from slag. 



6. Temperature. — As in the former work, the temperature 

 of the furnace is regulated by forcing the same quantity of 

 air swiftly through it at all times, but lading this air with 

 more or less illuminating-gas, supplied by a graduated stop- 

 cock. The amount of gas necessary in any case is determined 

 by trial, and observations are never to be taken except after 1 5 

 or 20 minutes' waiting, when the distribution of temperature 

 is found to be nearly stationary. Nevertheless the tempera- 

 ture of the crucible is never quite constant from point to 

 point. I therefore measured this datum at three levels — near 

 the bottom, the middle, and the top of the charge, after the 

 stationary thermal distribution had set in (see Tables, § 10). 

 For this purpose the fire-clay insulator*, tt, of the thermo- 

 couple, a b, passing through a hole in the lid, is adjustable 

 along the vertical. Before dropping the crucible the thermo- 

 couple is withdrawn from the charge and suspended above it. 

 The cold junction is submerged in petroleum and measure- 

 ments made by the zero method. 



When the charge is solid, a small platinum tube previously 

 sunk axially into the mass (see fig. 3) enables the observer to 

 make the three measurements for temperature as before. In 

 my later work I also encased the insulator of the thermocouple 

 in a platinum tube closed below (see fig. 1) when making 

 these measurements for the molten charge. Slag being a 

 good conductor at high temperatures, hydroelectric distor- 

 tions of the thermoelectric data may not otherwise be absent. 



I state, in conclusion, that when constancy of temperature 

 is approached the hole in the lid is closed with asbestos, and 

 the products of combustion escape by the narrow seam in the 

 side of the furnace, through which, moreover, crucible and 

 appurtenances are partially visible. 



* These are cylindrical steins, 5 centim. thick, 25 centim. long, with 

 two parallel canals running from end to end, through which the .platinum 

 wires are threaded. Cf. Bulletin U.S. Geolog. "Survey, No. 54, p. 95 

 (1889). c ~. Jf . ,l 



