Yes; and this new instrument has this additional advantage, that it does not fatigue the mouth and lungs like the common blow-pipe, and requires no art in blowing. MRS. B. Unquestionably; but yet this blow-pipe would be of very limited utility, if its energy and power could not be greatly increased by some other contrivance. Can you imagine any mode of producing such an effect? EMILY. Could not the reservoir be charged with pure oxygen, instead of common air, as in the case of the gas-holder? MRS. B. Undoubtedly; and this is precisely the contrivance I allude to. The vessel need only be supplied with air from a bladder full of oxygen, instead of the air of the room, and this, you see, may be easily done by screwing the bladder on the upper part of the syringe, so that in working the syringe the oxygen gas is forced from the bladder into the condensing vessel. CAROLINE. With the aid of this small apparatus, therefore, we could obtain the same effects as those we have just produced with the gas-holder, by means of a column of water forcing the gas out of it? MRS. B. Yes; and much more conveniently so. But there is a mode of using this apparatus by which more powerful effects still may be obtained. It consists in condensing in the reservoir, not oxygen alone, but a mixture of oxygen and hydrogen in the exact proportion in which they unite to produce water; and then kindling the jet formed by the mixed gases. The heat disengaged by this combustion, without the help of any lamp, is probably the most intense known; and various effects are said to have been obtained from it which exceed all expectation. CAROLINE. But why should we not try this experiment? MRS. B. Because it is not exempt from danger; the combustion (notwithstanding various contrivances which have been resorted to with a view to prevent accident) being apt to penetrate into the inside of the vessel, and to produce a dangerous and violent explosion. --We shall, therefore, now proceed in our subject. CAROLINE. I think you said the oxyds of metals could be restored to their metallic state? MRS. B. Yes; this is called _reviving_ a metal. Metals are in general capable of being revived by charcoal, when heated red hot, charcoal having a greater attraction for oxygen than the metals. You need only, therefore, decompose, or unburn the oxyd, by depriving it of its oxygen, and the metal will be restored to its pure state. EMILY. But will the carbon, by this operation, be burnt, and be converted into carbonic acid? MRS. B. Certainly. There are other combustible substances to which metals at a high temperature will part with their oxygen. They will also yield it to each other, according to their several degrees of attraction for it; and if the oxygen goes into a more dense state in the metal which it enters, than it existed in that which it quits, a proportional disengagement of caloric will take place. CAROLINE.