Heat and light, in their application to the manifold pur-pfises of life, are subjects of vast importance. As regard!! heat, an inexpensive process for producing high degrees is 'much in need ; and with respect to light, it is a brighter and cheaper form of artificial 1 i ght that is not liable to charge the air with carbonic acid which is wanted. The brilliancy of illumination, as well as the high degrees of temperature afibrded by the combustion of vario us gases in oxygen has, for many years past, led to zealous attempts to produce this gas at a cheap rate. There is, indeed, no want of oxygen ; it exists in immense quantities. The atmosphere surrounding our globe .consists of one fifth in bulk of this gas, and eight ninths of the weight of water, of which there is also no scarcity, is oxygen. But, in spite of all efforts bestowed upon the opening of these magazines for the uses referred to, the problem of the cheap separation of oxygen has only lately been solved. This discovery is due to two enterprising Frenchmen, Messrs. Tessie du Motay and Marchal; and it first excited attention at the time of the late Exhibition at Paris. Two substances, one a mineral, the other a product of manufacture —peroxide of manganese and chlorate of potash—have ordinarily been the source of oxygen ; this gas can be evolved from them with ease ; however, this process is too costly for use in the industrial arts. Besides this, various methods for producing oxygen have been proposed up to the year 1867. The one best known is, perhaps, that of Boussingault, which is founded upon the regeneration of the binoxide of barium. However, this process is now abandoned, chiefly on account of the cost of the crude material. Some years ago, Messrs. Saint Claire Deville and Debray were requested by the Russian Government to search for a better process for separating platinum from its ores. This metal can only be fused before the oxy-hydrogen flame, and there being large quantities of oxygen needed, a new mode of generating it, had to be sought for. The one proposed is based upon the property of the sulphate of zinc—a by-product of the cells of galvanic batteries—to split up into oxide of zinc, sulphurous acid and oxygen, when subjected to a red heat. The separation of these two gases is easily effected, since the one is absorbed by water while the other is not. The production of oxygen from the source referred to is very regular and un attended with d an ger ; moreover, it is economical as compared with those commonly employed by chemists ; in the experiments of Deville and Debray, the cubic meter (35'316 cubic fE-et) of oxygen when prepared from chlorate of potash could not be obtained for Ifss than ten francs (two dollars in gold); from manganese for not less than four francs, and in the last-described process, the price of one cubic meter amounted to only one franc and a half. By the discovery of Messrs. Tessie du Motay and Marchal the cubic meter of pure oxygen may now be produced for less than four cents, gold ; at least it is sold to the gas companies in Paris for t wenty-five centimes (five cents, gold) per cubic meter. We are consequently in possession of a process by which oxygen can be got at only one fiftieth of the cost of that ordinarily employed by chemists in their laboratories 1 The process of the French chemists is founded upon the fact that the manganate of soda at a red heat gives off a part of its oxygen when steam is passed through it, and that it re-absorbs oxygen when atmospheric air is passed through it This process may be represented by the following formula : 2 (Mn O3 Na 0) (manganate ot soda) + 2 H 0 (water)=Mn2 O3 (oxide of manganese) + 2 Na 0, H 0 (hydrated soda) + 80 (oxygen). According to this formula, the manganate of sod a is capable of producing fourteen and a halt per cent of oxygen in weight, and since the oxygen is 737 times lighter than water, from one hundred pounds of the crude product there can be generated 1,348 g:illons of oxygen, or something over five hundred cubic meters. With regard to the application of oxygen for illuminating purposes, it was first made in the square fronting the Hotel de Ville, one of the finest government buildings in Paris. This experiment, which lasted for about two months, not only met with perfect satisfaction, but also procured the patronage of his Majesty Napoleon III., who, for a second trial upon a still larger scale, ordered the court, of the Tuileries to pe illuminated by means of the oxy-hydric light. The grounds of that palace comprise in themselves an area of 36,000 square meters; besides, it has been introduced into one of the most spacious theaters of Paris, "La Gait," in the Alcazar, and in various stores and workshops. The light itself is produced by directing a j et of a mixture of oxygen and hydrogen or oxygen and street gas upon cones of zircone, a white earthy body, which has proved far superior to either lime or magnesia, that serves in the Hare, m-mond, or Calcium light. As regards the lightin g power, it is seven times ''greater than that produced by an equal quantity of street gas; i ndeed, the streets may be so brilliantly lighted with it that a newspaper can be read with perfect ease in a street car. Dr. Miler states that the oxy-hydrogen light can be seen at a distance, in a right line, of 112 miles. Navigable rivers might be cheaply and per'ectly lighted their whole length ; 375 andfcr churchos, workshops, theaters, and other spacious rooms, there is perhaps no mode of illumination better adapted than the new light. And, since the flame, when directed uI)Ou a solid, earthy body, it produces an emission of luminous, instea.! ot caloric rays the objection that it would heat, the room in which it is bumed,iis to the ground. But, in another point of view, the new li"htis far preferable to any other form of artificial light—we mean in regard to health. Accoi-ding to experiments recently undertaken by Dr. Zoch, in Germany, the quantity of carbonic acicd produced by a common gas flame in a room of the capacity of 2,540 cubic teet, may rise to the proportion of three parts to the thousand —a quautity generally supposed to be possible only in hospitals, prisons, and garrisons ; and what shall be said when it is considered that, in an ordinary parlor as many as three burners are kept constantly lighted' for five and six hours and with an inferior quality of gas at that '/ With respect to the oxy-hydric light, since the product of combustion is simply watery vapor, no vitiation of the air can possibly take place. As regards the application of oxygen for the production of heat, it may be stated that hydrogen, when being inflamed with oxygen, generates the highest heating effect known, with the exception of that of the electric discharge. This is due to the rapidity of the combination of these gases. Some years ago, by the construction of a close furnace of lime, and the use of the oxy-hydrogen blowpipe, MM. Deville and Du-bray were able, not only to volatilize many of the supposed fixed impurities in commercial platinum, but with aljout forty-three cubic feet of oxygen they have succeeded in melting twenty-five pounds of platinum in less than three quar-tel'S of an h'JUl', and casting it into an ingot, in a cake mold. And much larger quantities of platinum have more recently been fused by the same means. According to Brand and Taylor, silica and all metals are fused, and some of them entirely dissipated in vapor by the intense heat produced under these circumstances. The temperatures of various flames are, according to Prof. Bunsen : Oxy-hydrogen flame..................14,541 Fah. Hydrogen............................ 5,898" " Carbonic oxide....................... 5.507 " Coal gas............................. 4,262" " There remains no doubt that oxygen will soon play an important part in various branches of metallurgy, and those fully conversant with its properties, predict tor it not less conspicuous uses in other branches of art.