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A soft humming note began to vibrate through the inner laboratory a note which rose in pitch, steadily, as Herzog shoved the lever from one copper post to another, round the half-circle. "I am now heating the little firebrick furnace," said the scientist. "In Norway, they use an alternating current of only 5,000 volts, between water-cooled copper electrodes, as I have already told you.
This is also one of the avenues by which tool makers and moulders quickly reach the higher positions. I once wanted a Swiss watch maker. The cards turned one up he was running a drill press. The Heat Treat department wanted a skilled firebrick layer. He also was found on a drill press he is now a general inspector.
Few, if any, samples of firebrick will stand the heat of this blast, if the system is fully utilized. The only care needed is to see that you do not melt down the firebars during the process. I will also show you how, on an ordinary table, with a small pan of broken coke and the same blowpipe, used in the way already described, you can get a good welding heat in a few minutes, starting all cold.
What will raise the air to the required temperature, without in the process depriving it in any way of its vitalising elements, and without adulterating it with either smoke and fumes from leakage, or with particles of foreign matter given off from the material employed in its construction? There is nothing really better as a radiating surface than ordinary firebrick.
A closed gas stove is happily impossible, but the husband of the household is threatened with one of those beastly sham fires, wherein gas jets flare among firebrick a mechanical fire without vitality or variety, that never dances nor crackles nor blazes, a monotonous horror, a fire you cannot poke. That is what it will certainly come to if the problem remains unsolved.
In certain geological formations, the diatomaceae deposit, at the bottom of fresh-water ponds, beds of silicious shields, valuable as a material for a species of very light firebrick, in the manufacture of water-glass and of hydraulic cement, and ultimately, doubtless, in many yet undiscovered industrial processes.
Subliming. The subliming furnace, shown in Figs. 5 and 6, is a plain cylindrical chamber, A, about 4 ft. diameter inside and 4½ ft. high, lined with firebrick, in the center of which is fixed the upright cast-iron cylinder or retort, C, of 1 ft. diameter, closed at top and open at bottom. The furnace top is closed by a cast-iron lid, which is lifted off for charging the fuel.
Plenty of space is left for a bench or chair in this chamber. Adjoining is the laconicum with a firebrick furnace, after the nature of that of which I have before given full detailed drawings. The vitiated air is drawn through flues in the floor, to a shaft on the opposite side to the chimney. The stokery and coke-store adjoin the laconicum.
But the nature of the heating accomplished by means of steam-pipes is very inferior to that from large radiating surfaces of firebrick. The average temperatures of a public bath should range from about 110° in the shampooing rooms to 250°-260° in the hottest part of the laconicum, taking the readings of the thermometer at a level of 6 ft. 6 in. above floor-line.
The cylinder is internally lined with firebrick, projecting pieces causing the powdered ore to be raised over the flame through which it showers, and is thereby subjected to the influence of heat and to direct contact oxidation. The inclination of the cylinder, which is variable, promotes the gradual descension of the ore from the higher to the lower end.
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