Hydrogen gas in burning produces very little light: one cause of this is, that the product of combustion-formed water being in a state of steam, there is no solid substance in the flame; and it appears to be always true that no bright light can exist without a solid material. In order to produce a great light with the flame of hydrogen gas, it is only necessary to place a wire or a bit of flint, or any solid substance, in the flame. The solid immediately becomes intensely bright, and by using lime or magnesia, which are peculiarly fitted for the purpose, a light so intense as to be only surpassed by the noon-day summer sun, may be obtained. This lime light has been introduced for experiment into lighthouses, and has been particularly serviceable in the trigonometrical surveys of those kingdoms, in consequence of which it is generally known as the Drummond light, from the eminent philosopher whose recent melancholy loss every Irishman must deplore. The heat produced by the flame of hydrogen is thus most intense; substances which are inattackable by the strongest furnaces melt like wax in the jet of oxygen and hydrogen, and in the Drummond light the lime appears gradually to evaporate. A mixture of hydrogen and oxygen, or of hydrogen and air, may be thus set fire to by a candle; and when previously mixed, a terrific explosion is produced. Persons should therefore be very cautious how they perform experiments with hydrogen, as even skilful chemists have occasionally suffered severely from accidents of this kind. When a young person makes hydrogen for the first time, he is naturally curious, and hastens to satisfy himself by seeing that it burns: he applies the candle before all the common air has been expelled from the apparatus, and the mixture inside being still explosive, the flame passes back, and the whole is shattered into pieces with the noise and violence of a bombshell. At the same time, therefore, that we would be happy if this article induced many of our young readers to satisfy themselves of the composition and decomposition of water by actual experiment, yet we trust they will do so prudently, and with the guidance of some older person who has previously seen how chemical apparatus are employed.