Our readers have been made acquainted from time to time, with the progress of a light called the Oxygen Light, probably for want of a better appellation. The principles upon which this light is based, were stated in our report of the lecture delivered by Professor Doremus before the American Institute last winter, -rfhich will be found on page 87, Vol. 20 To save om readers trouble, we will, however, recapitulate the features of this improve^nt. The well-known calcium or Drummond light was produced by .irecting a jet of mixed oxygen and hydrogen upon a pencil or pure lime, the gases being conveyed in separate tubes or pipes, to within a very short distance from the aperture through, which they were delivered, and then flowing together and mixing in very minute quantity before combustion took place. This arrangement was adopted to secure safety, as these gases being mixed in the proportion of two of hydrogen to one of oxygen, the proportions best adapted to produce good results, form a very explosive mixture ; and as their combustion does not depend upon any external substance, the flame may, upon the removal of pressure, run back through a single tube containing the mixed gases to the receptacle where they are stored and produce serious disaster. The substitution of the common street gas for the pure hydrogen wad found, w. ile more convenient, to not greatly diminish the illuminating power. Oxygen was, however, until the discoveries of Tessie Du Motay and Marechal, an expensive gas to obtain unmixed, and the Drummond light was therefore only employed upon extraordinary occasions, its expense precluding its general and popular nse. The eminent scientists above named found that the salt called manganate of soda absorbed large quantities of oxygen under ordinary circumstances, and discharged it again when subjected to the action of superheated steam. By this means oxygen can be obtained sufficiently pure at a price, we are informed, not exceeding one dollar per thousand cubic feet. In the attempt to render this cheap oxygen in connection with the cheap street gas available in application to popular use, it was found that something more durable than the lime pencils was necessary. Pencils of magnesia were substituted and subsequently, of the oxide of zirconium ; and the light produced by the i gnition of these materials is undoubtedly the most brilliant and powerful light ever produced at a rate which could render its popular use practicable. The following objections have been made to this light; namely, the increased expense of the double service pipes required, the want of d iffasiveness in the light, which, although powerful, as we have stated it to be, is asserted to penetrate, rather than illuminate the surrounding space to a great distance; and, lastly, the danger which would attend. the introduction of inodorous explosive gases into dwellings. The expense of the service pipes is by no means a serious objection, as the cheapness of the lightif we accept the statements of those best informed in rer-ard to itwill render the introduction of the service a very profitable investment. The want of diffusiveness is an objection which only applies to the lighting of streets, squares, and parks ; and we have shown in a previous article, that this most probably arose, in the trial of this light in London, from placing it too low down. Any light requires for its proper diffusion a refracting and reflecting medium, and it would be easy to show by a diagram that the lower a light is placed the more of its rays will reach the ground and be absorbed without the possibility of reaching to remote distances. The objection made by the English journals in regard to the danger of introducing these gases into dwellings, will be found to vanish upon even a superficial examination. Oxygen and hydrogen mixed in the proper proportions are violently explosive. So is a mixture of common illuminating gas and air, nevertheless the gas now in general use is admitted to be the safest illuminating material ever generally adopted. But the latter has so strong an odor that it cannot escape even in small quantities, without being detected. It would not be difficult to mingle with the oxygen some odoriferous gas which would be wholly consumed in the ordinary course of burning, and the presence of which would evidence any leak in the oxygen pij- e. The street gas pipe would, as now, betray any leaks by the odor. Lastly, that any explosion may take place, both pipes must simultaneously leak at approximate pointsa contingency so remote that it does not Seem very frightful. We believe these gases may be carried into buildings with perfect safety, a^ that the increased purity of the air in rooms lighted by this method would be alone a.full compensation for all its drawbacks real and imaginary. We wefo present Itt an exhibition of this light Itt the works ef the Osfgsn Gaslight Company, in Fortytot street A New and Destructive Torpedo. The United States flagship Franklin, with Kear-Admiral Radford on Board, is at present in the Adriatic to test the qualities of the newly-invented torpedo, the story of which once appeared in this journal. The inventors of the machine claim for it, says the Pall Mall Gazette, a superiority over all other torpedoes now in use. First of all, it is a mere mine, to be exploded whenever chance may present a fitting occasion. It is a projectile which can be directed with an unerring accuracy against the object to be assailed, and this at a distance of several hundred yards. Secondly, it can be projected at any depth below water that may be required ; third-' ly, its explosive power is such as to make the strongest ironclads now afloat as much at its mercy as any wooden ship ; and lastly, the line of its direction may be made to curve or zig-zag, so that it can be used with safety in the immediate proximity of friendly vessels. As the United States Navy have lately embodied a special corps, chiefly for coast defenses, entitled the Torpedo Brigade, in which some of the most scientific officers have taken service, it is not without importance to know that by these same “ experts “ the Fiume invention has been pronounced a complete success. They have tested the machine by a variety of experiments, and without a failure in any. The resistance of water at a, certain depth to permit the downward course of a cannon shot, and the phenomena of “ ricochet” have lately occupied great attention in the American Navy, so that, whether the present invention could fulfill the difficult condition of preserving a uniform cours 3 at a depth, say fifteen or eighteen feet below the surface, was a most interesting problem to them. To ascertain this, nets were sunk at different distances along the course the torpedo was to take, and staffs with a graduated measure attached to them. By the replaced meshes the passage of the projectile was tested, and in a course of many hundred yards found not to have varied more than a few inches. Of course the principle of the invention is a secret, but the inventoror, more properly speaking, the perfector of the inventionan English engineer, Mr. Whitehead, has no hesitation in saying that he derived his first suggestion of the discovery from the mechanism of the fish, and that the peculiar mechanism and functions of what is called the “ swimming bladder,"' by whose agency the power to ascend or descend in water is secured, afforded him the first clue to his wonderful invention. The machine is about sixteen feet long, shaped like a fish, propelled by a screw, and guided by a rudder, so that, seen in the clear water, as one of the experimentalists described, its apparent vitality and volition were p»sitively horrifying. The Austrian Government, it is said, acting under the advice of Admiral Tegethoff, have purchased the use of the inventionthe patent remains with the inventorfor £20,000. Our own gove'nment deputed a commission to examine and report on it, and, it is believed or rumored, with approval of its efficiency. _Dr. Tyndall's Theory of Comets. Prof. Tyndall has developed a cometary theory out of his late researches upon the actinic power of light. It will be remembered that he has found that a beam of light is capable of forming a bright glowing cloud in its course through a space containing a modicum of vapor, the saia. cloud being first reduced by the chemical action of the light, arid then rendered visible by illumination of the condensed particles. The application of this principle to the explanation of cometary phenomena is as follows: A comet is held to be a mass of vapor decomposable by the solar light, the visible head and tail being an actinic cloud resulting from such decomposition. The tail is not matter proj ected from the head, but matter precipitated on the solar beams which traverse the cometary atmosphere ; nothing being carried from the comet to formrm the tail, but something being deposited from the interplanetary space through which the body is coursing. But this explanation supposes that the sunlight has a different power when it has passed through a vapory comet to that which it possesses when it has traversed no such medium ; otherwise all space would be lit up like a comet's tail. To account for such a peculiar property, Prof. Tyndall assumes that the sun's heating and chemical powers are antagonistic, and that the calorific rays are absorbed more copiously by the head and nucleus than the actinic rays. This augments the relative superiority of the actinic rays behind the head and nucleus, and enables them to bring down the'cloud which constitutes the tail. Thus the caudal appendage is in a perpetual state of renovation as the comets move throughspace; the old tails being dissipated by the solar heat as soon as they cease to be screened by the nucleus. Nearly all the phenomena observed in those mysterious bodies are accounted for by Dr. Tyndall. One, however, he has not mentioned; namely, the peculiar luminous envelopes, familiar to comet- gazers, which surround the nucleus like a series of cloudy glass cases. No theory can be called complete which doe? not account for thoss mmnrkfthfe »nd eTld..l;lB.tlf imports,! featttfsis © 1869 SCIENTIFIC AMERICAN, INC.