Among the most recent researches on the subject are those of Mr. Knoblauch (of which a translation is given in Taylor's Foreign Scientific Memoirs, Part xviii. and xix.), and they are not to be surpassed for extent and accuracy of detail.

One series is devoted to the examination of the alleged differences in radiation of heat proportioned to the temperature of the source. This, as before observed, is an untenable hypothesis, but Mr. Knoblauch distinctly refutes it by a series of experiments on alcohol flame, red-hot metal, hydrogen flame, and an Argand lamp, whose temperatures are in the order of enumeration beginning with the highest; but the power of their heat to penetrate screens is found to follow exactly the reverse order. And even with lower stages of heat, the effects bear no proportion to the temperatures as such. Hence the effect is evidently not due to a mere extrication of the heat of temperature, but is of a peculiar kind. In a word, agreeably to the preceding remarks, the different species of rays, more or less compounded together in the several cases, exhibit their diversities of character in developing heat by their absorption. One very peculiar result is, that platinum, at a stage intermediate between red and white heat, transmits through all the screens employed rather less heat than when at a red heat. That is, these intermediate rays are of such a wavelength as to be subject to a peculiar absorption by these screens ; while at the same time possibly less of the former may be emitted.

In another section Mr. Knoblauch adverts to the effects of surfaces on the absorption of rays, and particularly remarks (p. 205), “The experiments of B. Powell and Melloni have shown that one and the same body is not uniformly heated by rays from different sources, which exert the same direct action on a blackened thermoscope; a statement which does not very intelligibly express any conclusion of the author's. Mr. Knoblauch however supports it by elaborate experiments, showing, as might be anticipated, that an Argand lamp affects a surface of carmine less, and one of black paper more, while a cylinder heated to 212° affects the carmine more and the black paper less.

Another extensive series, on the effect of surfaces on radiation, is directed to show that the effect is independent of the source whence the heat so radiated was originally obtained.

Among the very multifarious results referring to screens and surfaces obtained by Mr. Knoblauch, it can here only be remarked that none of those varied facts appear to present anything at variance with the principles here advocated, while in the general conclusions which he indicates at the close of his memoir, the author, though professedly avoiding all hypothesis, yet distinctly intimates his conviction of the heterogeneity of the heating rays increasing as the condition of the source rises in the scale from a low heat up to luminosity or combustion: and that the diversities of heating effect on different media are due to a selective absorption of particular species of rays, from peculiarities in the nature of those substances, and analogous to the absorption of particular rays of light by coloured media.

It must not however be omitted to notice, however briefly, another recent set of researches of high interest, those of M. Silberman; in which (among others) the very remarkable fact is established, that on transmitting a narrow ray of heat from a heated wire, through rock-crystal, there is a singular difference according as the ray passes parallel or perpendicular to the axis of the crystal: the effect being indicated by having the further side of the crystal coated with a fine composition of wax, the portion of which in the direction of the ray is melted in a circular form in the first instance and in an elliptical in the second.

The general fact of the heterogeneity of heating rays, especially from luminous sources, is fully recognised by Melloni as in some sense the conclusion from all his experiments.

The hypothesis that this heterogeneity consists simply in differences of wave-length would seem a probable one; though it is still possible, as Professor Forbes suggests, that some other element may also enter into the conditions.

This view has been extended by M. Ampère so as to refer both luminous and heating effects to the same rays :-a view controverted by Melloni, chiefly on the ground, evinced by several classes of experiments, that the intensity of the heating effect (especially in the solar rays) follows no proportion to that of illumination; an argument which really amounts to little, unless the theory obliged us to infer that the amount of illumination must follow the same law as that of heat; which it manifestly does not; since the nature of the effect in the one case is wholly dependent on the unknown constitution of the optic nerve; according to which some precise proportion of the impinging vibrations, with a particular wave-length, is that which gives the greatest perfection of vision; while for heat the effect has no reference to such peculiar conditions, but is dependent in some way on longer wave-lengths, and probably more simply connected with the intensity or amplitude of the vibrations.

On this theory our view of the case would be thus :

A body heated below luminosity begins to give out rays of large wave-length only. As it increases in luminosity it continues to send out these, and at the same time others of diminishing wave-lengths, till at the highest stage of luminosity it gives out rays of all wavelengths from those of the limit greater than the red end of the spectrum, to those of the violet end, or possibly less.

Rays of all these species are transmissible and refrangible by rocksalt; and many of them with numerous specific distinctions by other media.

They are all more or less capable of exciting heat when absorbed or stopped; though in some the effect is perhaps insensible. Both this property and that of their transmissibility seems to depend in some way on the wave-length, though in no simple ratio to it.

The absorptive effect due to texture of surfaces has some direct relation to the magnitude of the wave-length, especially near the limit; while that due to darkness of colour is connected with

shorter wave-lengths, such as belong to rays within the limits of the light spectrum: and in any case when a ray impinges on any absorbing substance, its vibrations, being stopped, communicate to the molecules of the body vibratory movements of such a kind as constitute heat of temperature.

We

The peculiar molecular constitution of bodies which determines their permeability or impermeability to rays of any species, gives rise to all the diversities of effect, whether luminous or calorific. thus escape all such crude ideas, at once difficult and unphilosophical, as those either of two distinct material emanations producing respectively heat and light, or of a conversion of one into the other; and obtain a view far more simple and consistent with all analogy.

LXXV. Intelligence and Miscellaneous Articles.

DR. KEMP'S PATENT FOR A NEW METHOD OF OBTAINING MOTIVE POWER BY MEANS OF ELECTRO-MAGNETISM.

MY

Y invention of a new method of obtaining power by means of electro-magnetism consists of the mode hereinafter described of combining apparatus to be actuated by electro-magnets. And in order that my invention may be most fully understood and readily carried into effect, I will proceed to describe the means pursued by me. I so arrange electro-magneto apparatus that a series of electromagnets are caused to act in succession by their armatures on the same bar or instrument, and by such bar or instrument I give motion to fluids in order to obtain and communicate power thereby. To accomplish this object the armatures of several electro-magnets are fixed to stems, and the stems of the armatures are to be free to move through the bar or instrument which carries them. For the purpose of enabling the armatures to be acted on in succession by their magnets, I make the stem of the armature which is to be first attracted somewhat longer than the next in succession, by which means the first armature will be as near as may be to its magnet; and the next armatures being more and more distant from their electro-magnets, therefore when the first armature has been attracted by its electro-magnet, the others will be moved nearer to their electro-magnets, and will consequently be brought into the most advantageous position to be attracted thereby when their turns come. Thus, supposing it to be determined that each armature shall be attracted through a quarter of an inch by its electro-magnet, and that there are to be eight electro-magnets to act on the same bar or magnet, the first armature before being attracted would be at a distance of a quarter of an inch from its electro-magnet; the second would be half an inch from its magnet; the third three quarters of an inch from its magnet, and so on; whereby the eighth armature would be two inches from its electro-magnet, and these differences of distance are to be obtained by the stems (by which the armatures are connected to the bar or instrument) being made shorter and shorter. By this arrangement it will be evident that if electric currents be caused to pass in succession to the coils of the several

electro-magnets, and in such manner that the currents of electricity having caused the first electro-magnet to attract its armature, are cut off therefrom, and caused to pass to the next electro-magnet, and so on in regard to the eight electro-magnets and their armatures; each armature before being attracted will have been brought by the movement of the bar or instrument to within about a quarter of an inch of its electro-magnet, the bar coming at each step of its movement nearer and nearer to the electro-magnets, which it is enabled to do by the stems of those armatures which have been previously attracted, being enabled to slide back freely through the bar or instrument which carries them. The stems of the armatures are enabled to draw the bar or instrument towards the electro-magnets (when their armatures are attracted by reason of the stems having projecting heads or end), which prevent the stems from being drawn through the bar or instrument which carries them, whereby, when all the electro-magnets have attracted their armatures, the bar or instrument will have been moved two inches or other distance according as arrangement is made for each of the electro-magnets to act through a less or larger space than a quarter of an inch. It will be evident that this bar or instrument may be arranged to give motion to machinery in various ways; but I believe the most convenient mode of applying the power thus derived from electro-magnets, will be found to be to affix one bar or instrument, such as herein described, to one end of the rod of a piston working in a cylinder, and another such bar or instrument to the other end of the piston-rod, the piston being in the middle of the piston-rod, and the piston-rod working through stuffing-boxes on the covers at either end of the cylinder. Each such bar or instrument is to be fixed in the manner of a cross-head to the piston-rod, and to be guided in its movement to and fro, and is to be provided with armatures on stems as herein described, and sets of electro-magnets to attract the same, and capable of being brought into action in succession, as above explained, and as will be readily understood by workmen accustomed to making electro-magneto apparatus; by which means the piston in the cylinder may be moved first in one direction and then in the other. In order that the armatures may be in a position to act correctly, the ends of their stems, when being moved back towards the cylinder, should come against a stop or stops to move the heads or enlarged ends of the stems to the bar or instrument which carries them; they will thus be brought into position to be again acted on by their electro-magnets so soon as the electro-magnets have, by attracting their armatures, drawn the piston, as far as it can go, in the other direction. As a piston, by such means, cannot with convenience be caused to move through an extended length of space, the cylinder is to be of comparatively large diameter to its length, and at either end it is to have passages for the water or other fluid (contained in the cylinder) to pass into and from the ends of another cylinder of less diameter, but of proportionably greater length, in which a piston also works; and I prefer that the piston-rod of such second cylinder should also work through stuffing-boxes at either end of that cylinder; such piston-rod communicating the power

obtained (by the means above described) by a connecting-rod and crank from one end of the piston-rod, or by other suitable means of communicating power from a piston, may be employed. From the above description it will be understood that great power may be obtained from a series of electro-magnets, each attracting its keeper or armature, and consequently moving the piston through only a small space; and such power being exerted over a large area of piston, moving a fluid and forcing it into a cylinder of smaller diameter, will cause the piston of that second cylinder to be moved through a longer stroke in proportion to the different capacities of the cylinders, and the piston of the second cylinder will consequently be moved at a greater speed than that in the larger cylinder, and the pressure per square inch on the smaller piston will be the same as that on the greater piston. All which will be readily understood by a workman acquainted with the pressure of fluids put in motion by one piston, and caused to act on another; and it will be at once perceived that the action will be the reverse of that in Bramah's Press, wherein the water is put in motion by the power used acting on a piston or plunger of comparatively small diameter, and the water is caused to act on and to move a piston of much larger diameter. Whereas, in the present invention, a series of electro-magnets are caused to act in succession on a bar or instrument, as above explained, in such manner that when combined with a comparatively large piston the power will, by driving or forcing the water or fluid with a cylinder of less diameter and of greater length, cause the piston therein to be moved with less power, but with greater speed. And it will at once be understood that the power obtained will depend on the effort each magnet is capable of exerting; for it will be evident that the actual force which is kept up to and given off from the piston in the small cylinder will be equivalent to that exerted by one of the magnets, in attracting or drawing its armature through a comparatively small space.-Repertory of Patent Inventions, February 1852.

ELECTRO-CHEMICAL RESEARCHES ON THE PROPERTIES OF ELECTRIFIED BODIES. BY MM. FREMY AND BECQUEREL.

For several years the attention of chemists and physicists has been directed to the very remarkable modifications which certain bodies present when submitted to the action of a moderate temperature. We know that, under this influence, sulphur and phosphorus acquire new properties. We propose to investigate whether electricity, like heat, can change the physical and chemical properties of different bodies. We must examine, in the first place, into the singular effects presented by oxygen in various circumstances, and referred to the formation of what has been called ozone; this body appears to be produced in all cases in which oxygen is submitted to the influence of electricity.

Without wishing to cast doubt upon the sagacity of those who have examined into the properties of ozone, it cannot be denied that there still exists great uncertainty in the minds of chemists and phi losophers as to the interpretation of the phænomena observed; we