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r soften at certain different temperatures. In all his ten tests the alloys melting at 120° C. were fused completely; in two tests other alloys melting at 216° and 240° C. showed signs of fusion; and in one test an alloy melting at 280° C. began to soften. Working with an experimental apparatus constructed on the "dripping" principle-- _i.e._, a generator in which water is allowed to fall in single drops or as a fine stream upon a mass of carbide--with the deliberate object of ascertaining the highest temperatures capable of production when calcium carbide is decomposed in this particular fashion, and employing for the measurement of the heat a Le Chatelier thermo-couple, with its sensitive wires lying among the carbide lumps, Lewes has observed a maximum temperature of 674° C. to be reached in 19 minutes when water was dripped upon 227 grammes of carbide at a speed of about 8 grammes per minute. In other experiments he used a laboratory apparatus designed upon the "dipping" principle, and found maximum temperatures, in four different trials, of 703°, 734°, 754°, and 807° C., which were reached in periods of time ranging from 12 to 17 minutes. Even allowing for the greater delicacy of the instrument adopted by Lewes for measuring the temperature in comparison with the device employed by Caro, there still remains an astonishing difference between Caro's maximum of 280° and Lewes' maximum of 807° C. The explanation of this discrepancy is to be inferred from what has just been said. The generator used by Caro was properly made of metal, was quite small in size, was properly designed with some skill to prevent overheating as much as possible, and was worked at the speed for which it was intended--in a word, it was as good an apparatus as could be made of this particular type. Lewes' generator was simply a piece of glass and metal, in which provisions to avoid overheating were absent; and therefore the wide difference between the temperatures noted does not suggest any inacc