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Prof. Faraday recently delivered a lecture at the Royal Society, in explanation of the late experiments and researches ot Bous-ingault, Fremy, Becquerel, and other continental chemists, respecting the generation and the nature of oxygen. As that element constitutes at least one-half of the substances on the surface of the earth, and is an active agent in most chemieal decompositions, the determination of its properties is extremely interesting and important; the importance of such investigations having been increased by the recently-discovered magnetism of oxygen gas, which has become very interesting by the new theory based upon it by Lieut. Maury, U. S. N., as the cause of the circulation of the winds, and by other qualities that point out its agency in various operations of nature that are at present but imperfectly understood. The researches of Boussingault have been principally directed to the means of obtaining a supply of oxygen on a large scale for its application to practical purposes. His principal aim was to separate the oxygen from the nitrogen with which it is mixed in the atmosphere, and from that exhaustless source to procure it in an economical manner. The combinations of oxygen with mercury by means of heat, and their separation by the application of a higher temperature, suggested the principle on which the experiments were Konducted. When, for example, mercury is subjected to a temperature just above its boiling point, the vapor combines with the oxygen ot the atmosphere, and forms a peroxide; and that substance when exposed to a higher degree of heat, is decomposed, and one-half of the oxygen is liberated. In this manner by variations ol the temperature alone, oxygen is first abstracted from the atmosphere, and solidified in mercury, from which it is afterwards expelled in a gaseous state. Boussingault found that baryta could be made to act in a similar way, and much more economically. After innumerable experiments, in which he had to encounter and overcome vanous practical difficulties, he succeeded in contriving a mode o) operating from which he expects to obtain important results. He encloses the baryta in a retort open at each end, through which a current of stem is transmitted. The retort is placed in a furnace that can be heated to any required degree. The baryta when operated on in this manner, at a ceitain temperature, doubles its former quantity of oxygen, and is converted into a peroxide. The supply of steam is then cut off, the heat of the furnace is raised, and a communication by a separate tube having been made with a gasometer, the oxjgen absorbed during the former process is expelled in a gaseous state and collected.— The same baryta may be operated on any number of times, without requiring change or addition, and the oxygen gas thus obtained is of the purest kind. It is estimated that with an apparatus of this kind, containing only 24 lbs. of baryta, about 200 pints of pure oxygen gas may be generated in 24 hours, and, by enlarging the size of the apparatus, that a sufficient supply of oxygen gas may be procured to allow of its being applied practically to many useful purposes. Professor Faraday expressed doubts whether the plan proposed would be sufliciently economical for general application, but he said it was, at all events, an important step towards the accomplishment of so desirable an object. Several experiments were made to show the uses to which oxygen gas might be advantageously applied if it could be procured in abundance au a cheap rate, especially as a means of increasing the illuminating power of coal gas. In noticing the difficulties that Boussingault had to overcome, Professor Faraday mentioned that in the first experiments with baryta he had carefully excluded water from the appa-tus, conceiving according to previously received opinions, that its presence would be detrimental to the absorption of the oxygen from the air. Under these circumstances, it was found that the baryta after having been once operated on, did not absorb oxygen freely a second time until it had been exposed to the atmosphera. Boussingault was for a long time at a loss to account for this perplexing occurrence, when he at last discovered that aqueous vapor, which he had been so careful to exclude, was necessary to restore the absorbing power. The researches of Fremy and Becquerel relate principally to the identification of ozone with oxygen, which they have very satisfactorily proved. The change oxygen undergoes in its conversion into ozone, and the peculiar bleaching properties it acquires, has given rise to interesting speculations respecting the mode of action of that body, and even thrown a doubt on its elementary character.
