Proceedings of the British Association. 485 



having different optical properties. Finding difficulty in proceeding 

 with these experiments, at the heat given by ordinary furnaces, and the 

 risk to which the platina crucibles were exposed, he was induced to 

 try the effects of hydrogen burning in common air. Dr. Dalton was 

 consulted on the construction of the first hydrogen furnaces, and he 

 suggested the difficulty which was found to arise in practice — that hy- 

 drogen gas burning, through small orifices, with great pressure, would 

 blow itself out. This difficulty was, however, overcome in the manage- 

 ment of the apparatus brought before the Section. This apparatus 

 consisted of an iron tube, in which the gas was generated by the addition 

 of 15 ounces of zinc to three-quarters of a pint of oil of vitriol and ten 

 pints and a half of water. The gas produced was found to be in ten 

 minutes under a pressure of 21 atmospheres, in sixteen minutes and a 

 half under a pressure of 25 atmospheres, and in eighteen minutes under 

 a pressure of 26 atmospheres. The gas was conducted into another 

 cylinder, and from thence to the jets, over which was suspended a 

 platina crucible. The gas being ignited at these jets, maintained, with 

 the above charge, the platina crucible at a white heat for twenty 

 minutes. Gems had been fused by the heat thus generated. Several 

 kinds of jets were used, as it might be necessary to surround the crucible 

 with heat, or only to apply the heat to the bottom of it. Experiments 

 with this apparatus have been made upon the phosphates of antimony, 

 zinc, barytes, and cadmium. The results have not been, however, quite 

 satisfactory. In some the striae interfered with the transparency of the 

 glass formed ; and in the case of the monobasic phosphate of zinc, it 

 was found that, to whatever heat the compound may have been exposed, 

 the glass thus formed was deliquescent. The reading of this Report was 

 accompanied by some experiments with the hydrogen furnace in question, 

 for the purpose of showing the intense heat which could be produced. 



Dr. Faraday bore testimony to the advantages of this arrangement. 

 He had found in all his experiments on glass, in which the elements 

 were chemically combined, that crystallization took place. He regarded 

 all common glass as examples of solution, rather than of chemical 

 combination. Borate of lead and silicate of lead, if fused in small 

 quantities, so that they cooled quickly, were transparent, but if fused in 

 masses, which required a longer time, they were in a crystalline condi- 

 tion. — Mr. Harcourt remarked, that in the monobasic phosphate of zinc, 

 which was transparent when vitrified, the quantity of acid was probably 

 exceeding small, but this glass was striated. — Dr. Faraday said, that 

 some of the purest specimens of American ice show similar striae 

 although it was in a state of exceeding purity, yielding the purest of all 



