Scientific Memoirs

Front matter

SCIENTIFIC MEMOIRS,

SELECTED FROM

THE TRANSACTIONS OF

Volume 1

SCIENTIFIC MEMOIRS,

SELECTED FROM

THE TRANSACTIONS OF

FOREIGN ACADEMIES OF SCIENCE AND LEARNED SOCIETIES,

AND FROM

FOREIGN JOURNALS.

EDITED BY

RICHARD TAYLOR, F.S.A.,

VOL. I.

LONDON:

PRINTED BY RICHARD AND JOHN E. TAYLOR,

RED LION COURT, FLEET STREET.

1837.

PREFACE.

In the publication of the four parts which complete the present volume of the Scientific Memoirs, I have ventured to make the experiment how far I might be able to succeed in supplying an auxiliary which, as was stated in the Advertisement prefixt to the First Part, appeared to be much needed for the progress and advancement of science in this country.

My own conviction of the utility of such a work has been much strengthened since I have been engaged in it, both by the importance of the materials that present themselves, and by the expressed opinions of persons most competent to judge. How great indeed the disadvantage must be, under which those are placed who are engaged in any branch of scientific inquiry, from being uninformed as to what is doing, or has been done, by our active and laborious neighbours on the Continent, must be obvious to every one: and the cases are numerous to which the remark of Lenz, p. 312, speaking of Ohm's theory of the galvanic battery, will apply,—that, although given to the world several years ago, yet, “being only published in the German language, it is unknown both in France and in England.”

With regard to the execution of the work, I must submit it to the candid judgement of those who are aware of the difficulty of the task,—having availed myself of the valuable suggestions with which I have been favoured in the selection of memoirs, and of the best assistance within my reach for their translation. I shall be satisfied if what has been done should render the present volume useful to science, and if what there is still to do should induce the public to enable me to continue the work. Hitherto, as I can hardly yet boast of the sale of 250 copies, I am very far from having been repaid the cost of publication, to say nothing of the care and labour which have been required: nor could I be expected, having now finished a volume, which, from the nature of its materials, may be considered a complete work in itself, to proceed further unaided, until I have ascer whether I may calculate upon adequate support. This, however, I cannot yet think it improbable that I shall obtain, when the plan and contents of the present volume shall have become better known; and with this view, I shall gladly receive the names of those who may be disposed to uphold the work by purchasing what has been published, and forming the list of my future subscribers.

I should hardly have been disposed to persevere further, had it not been for repeated expressions of strong interest in the success of the work, which have reached me from persons of the highest scientific eminence; among whom I may perhaps without impropriety mention the names of Ivory, of Babbage, Powell, Forbes, Lloyd, Challis, Owen, Wheatstone, Phillips, Talbot, Hamilton, Faraday, and others in this country, and of Hare, Henry, and Bache in the United States. To several of them I have been indebted for very important suggestions; and to Professor Wheatstone especially, for his valuable contributions.

From the kind assistance of men of science, and from an increased acquaintance with the sources whence the best materials are to be derived, I think I may fairly hold out to the public the prospect of some considerable improvements in the work: and I shall be thankful for any suggestion for this purpose. I may perhaps give the titles or early notices of such foreign scientific papers as shall not be adopted for immediate translation: and as our first volume may be said to have cleared off some arrears, we may now come nearer to the present time, and endeavour to supply what is of the latest date and of intrinsic value.

However, this, as I have already stated, must depend upon my prospect of future support, and the success of the present volume;—and, glad to have finished my humble but laborious task in completing it, I shall be able at my leisure to decide as to the future.

RICHARD TAYLOR.

Red Lion Court, June 29, 1837.

CONTENTS OF VOL. I.

PART I.

PART II.

PART III.

PART IV.

Errata

ERRATA.

Page | 156, line 4, for 8-35. read 5-35

— | 158, line 37, insert a comma after Calcium

— | 160, line 41, for 0.350 carbon read 0.350 carbonic acid

— | —, line 43, for 0.450 carbon read 0.450 carbonic acid

— | —, line 43, for 0.0759 read 0.075 water

— | 162, line 3, for sesquichromate read sesquichloride

— | 164, line 6, for them read bases

— | —, line 22, for .754 read 0.734

— | —, line 34, after stated that insert from

— | —, line 34, omit contained

— | —, line 35, after chloride of spiroil insert more obtained

— | —, line 37, for 11.56 read 111-56

— | 165, line 18, for 0.510 water read 0.119 water

— | 470, line 5, for vol. xvi. read vol. lxvi

— | —, four lines from bottom, for (Reamm.) read (Centigr.)

— | 471, last line, for precipitated read before-mentioned

— | 472, line 11, for in the same manner, read of the same kind

— | —, line 33, for discoloured read decoloured

— | —, line 41, for — 15° read 15°

— | 473, two lines from bottom, for give them read give it

— | 474, three lines from bottom, for of read and

— | 475, line 28, for Ka² read Ka₁

— | 476, line 6, for sulphur read sulphite

List of Plates

LIST OF PLATES.

|I. | M. Melloni's Experiments on the Immediate Transmission of Radiant Heat, pp. 42 and 55.

|II. | Dove's Apparatus for the Polarization of Light, p. 79.

|III. | Savart's Researches on the Elasticity of Bodies by means of Sonorous Vibrations, p. 143.

|IV. | Savart's Researches on the Elasticity of Bodies which crystallize regularly, p. 262.

|V. | Burmeister's Remarks on the Sound produced by Insects; and Ehrenberg's Memoirs on Fossil Infusoria, pp. 378 and 413.

|VI. | To illustrate Baron von Wrede's Memoir on the Absorption of Light, p. 480.

|VII. | Jacobi's Electro-magnetic Machine, p. 507; and Schulthess's Electro-magnetic Machine, p. 539.

Memoir on the Free Transmission of Radiant Heat through different Solid and Liquid Bodies

SCIENTIFIC MEMOIRS.

VOL. I.— PART I.

Article I.

Memoir on the Free Transmission of Radiant Heat through different Solid and Liquid Bodies; presented to the Royal Academy of Sciences of Paris, on the 4th of February, 1833, by M. Melloni.

From the Annales de Chimie et de Physique, t. liii. p. 1.

Mariotte was the first, so far as I am aware, who attempted to appretiate the action of diaphanous substances in transmitting or intercepting the calorific rays which emanate from terrestrial sources. After having observed that solar heat concentrated at the focus of a metallic mirror, suffered no sensible diminution of intensity by being made to pass through a glass plate, he took and placed his apparatus before the fire of a stove, and found, that at the distance of five or six feet the temperature of the reflected image at the focus, when the rays were allowed to meet there without impediment, was such as the hand could not bear; but that when the plate of glass was interposed there was no longer any sensible heat, although the image had lost none of its brilliancy. Whence he concluded that none, or certainly but a very small portion, of the heat of terrestrial fire passes through glass.

About a century after Mariotte's time, the same experiment was repeated by Scheele, who, instead of imitating the cautious reserve of his predecessor, asserted that from the moment when the glass was interposed there was no longer any heat whatever at the focus of the mirror. Pictet, however, corrected the mistake by means of the apparatus known by the name of conjugate mirrors. A very transparent square of glass was placed between a thermometer and the heat of a lighted candle concentrated by the apparatus; the mercury in some moments rose several degrees; there was a perceptible elevation of temperature also when the candle was removed and a small jar filled with boiling water put in its place.

Some years later Herschel undertook a very extensive series of experiments on the same subject. They are described in the volume of the Philosophical Transactions for 1800. The author employs no artifice to increase the action of the rays of heat, and contents himself with the direct measurement of their effect by placing the thermometer at a very short distance from the diaphanous body.

But doubts were started as to the conclusions drawn from these different results. It was objected that part of the radiant heat was first stopped at the nearer surface of the glass, that it was gradually accumulated there and afterwards propagated from layer to layer, until it reached the further surface whence it began again to radiate on the thermometer. It was maintained even that nearly the whole of the effect was produced by this propagation. In short, some went so far as to deny altogether that the heat emitted by terrestrial bodies can be freely transmitted through any other diaphanous substance than atmospheric air.

M. Prevost, by means of a very ingenious contrivance, demonstrated the erroneousness of this opinion. Having attached to the pipe of a fountain a spout consisting of two parallel plates, he obtained a strip of water about a quarter of a line in thickness. On one side of this he placed an air thermometer and on the other a lighted candle or a hot iron. The thermometer rose, almost always, some fraction of a degree. Now it is quite evident that, in this case, a successive propagation through the several layers of the screen, which was in a state of perpetual change, could not take place. It was admitted, therefore, that other diaphanous media besides atmospheric air sometimes transmit the rays of heat as instantaneously as they always transmit those of light.

M. Prevost's process could not however be applied to solid bodies. It was therefore impossible to determine, by means of it, whether caloric was immediately transmitted through screens of glass. Delaroche completely solved this problem by employing a method invented by Maycock. The method consists in observing the thermometer as in the preceding cases; that is, when the caloric rays fall upon it after having passed through the plate of glass. We thus obtain a complex measure of the effects produced by immediate transmission and by that conducting power of the layers to which we have given the name of successive propagation. If we know the value of either of these, we have that of the other. Now it is easy to determine the influence of the conducting power by repeating the experiment after having blackened with Indian ink that surface of the plate which is turned towards the calorific source. In this case, the immediate radiation being intercepted, it is clear that the elevation of the temperature at the other side must be attributed only to the conducting power of the layers. Should the elevation be now found less than it was at first, it will be a decisive proof of immediate transmission. And such was the fact in almost all the experiments of Delaroche; I say almost all, because it was found that the quantity of heat freely transmitted varied with the temperatures of the source. For temperatures lower than that of boiling water it was nothing, and when an Argand lamp was employed, it was found to be more than half of the whole quantity.

No doubt can be raised as to the truth of this beautiful discovery of Delaroche; and yet the method which he has employed to measure the quantities of heat freely transmitted is by no means exact, especially in respect to high temperatures. In order to understand this seeming paradox two things are to be observed; 1st, the difference produced by change of surface between the two quantities of heat which penetrate the glass by reason of its conducting power; 2nd, the difference produced between those two quantities by the total or partial interception of the calorific rays.

It is fully proved by the experiments of Leslie and others, that glass, when blackened with Indian ink, absorbs all the rays of heat, though, in its natural state, it reflects a certain number of them. The quantity of heat which penetrates the screen will therefore be greater in the former than in the latter case. However, as polished glass reflects but a very small portion of caloric rays, the error arising from a difference in the state of the surface will be reduced to a very inconsiderable quantity and may be safely disregarded. But the case is different when we examine the error produced by the total or partial interception of the caloric radiation. In some of the experiments of Delaroche one half, at least, of the incident rays immediately passed through the screen. Thus it was evident that it was the other only which was stopped at the first surface of the glass. The effect of conduction must therefore be limited to this latter half. But as the screen, when blackened, stops the whole radiation, it is then exposed to a heat twice as strong, and therefore exhibits a far greater effect of conduction. Hence it follows that when we deduct from the observation furnished by the transparent glass the observation furnished by the glass blackened, the result obtained will be lower than the true temperature of the rays transmitted freely. But the error will not be the same in all cases. Being of no account when boiling water is employed, it will increase in proportion as the temperature of the source is raised. The measures of the free radiations which suffer the greatest diminution will be those furnished by the highest temperatures. Hence it is evident that this latter cause of error in the measure of the immediate irradiation, instead of invalidating the law of Delaroche, serves only to give it greater certainty. We are therefore justified in saying, as we have said, that the want of exactness in the method has no influence whatsoever on the truth of the law which it has served to establish.

To Delaroche we are also indebted for a discovery, no less important than the foregoing, relative to the amount of loss sustained by the same rays of heat in passing successively through two squares of glass. But I abstain, for the present, from entering into any detail on this subject, as I shall have occasion to speak of it hereafter.

None of those whose labours we have been thus briefly noticing has thought of making an exact comparison between the transmissions of caloric rays through screens of different kinds; and, if we except the experiments of M. Prevost and those of Herschel, from which no consequence can be deduced, all the others were confined to the single purpose of ascertaining the law of transmission through glass only. Neither has sufficient attention been given to the influence of the state of the surface, or that of the thickness of the layers and their internal structure on the quantities of heat which freely pass through them. I have endeavoured to supply these different omissions, but the undertaking has proved too vast for me, and several parts of it are therefore incomplete. I hope however that I shall be able hereafter to return to these, and to treat them in a manner more satisfactory.

In the mean time I present to the Academy the results of my first researches disposed in two memoirs. That which I offer at present contains an account of the method pursued in the measurement of calorific transmission and the application of the method in the case of an unvarying source acting on bodies of different kinds. In the second I shall explain the facts connected with the succession of the screens and the variation of the sources.

General Considerations on the Free Transmission of Caloric through Bodies, and the Manner of Measuring it by means of the Thermomultiplier.

We have already observed that a diaphanous screen placed at a certain distance from a calorific source stops a portion of the rays which strike its first surface, while the rest pass freely through. We have remarked besides that after a certain time the heat stopped at the anterior surface, and accumulated there by successive radiations, passes on from layer to layer till it reaches the other surface, whence it begins to radiate anew; and that this radiation mingling with the heat which passes through the screen by immediate transmission, prevents its being measured exactly.

When the screens are liquid, the influence of the conducting power of the layers may always be destroyed if we incessantly renew the matter of the screen by means analogous to the strip of water employed by M. Prevost. But it would be always very difficult, and often impossible, to apply this artifice to solid bodies and even to such liquids as can be obtained only in small quantities. In order therefore to attain the same end in a general manner, and to render the experiments in some degree independent of conduction, other means must be employed.

If we consider with due attention the manner in which the second surface of the interposed plate is heated, and the radiation which results from it, we shall see that the latter possesses properties very different from those that belong to the caloric which is freely transmitted. In order to be satisfied of this, we have only to observe that its action changes with the change of distance between the screen and the source; a thing which does not happen, even in the slightest degree, to those rays that are transmitted freely. In fact, it is with the caloric transmitted immediately, as it is with light.

If between the flame of a candle and the eye we interpose a plate of glass or any other substance more or less transparent, we find the diminution of the intensity of the light always the same, however the distance between the plate and the candle may vary. The effect produced by distance on the freely transmitted caloric is exactly similar; and if at a certain distance from the active source there be a thermoscopic apparatus sensible to this portion of heat, the apparatus will always give the same indication, whether the screen be laid close to the source or to the thermoscope.

But it is clear that it must happen quite otherwise to the conductible caloric; for this portion of the heat, when it has reached the further surface of the screen, leaves it in the form of diverging rays which become weaker in proportion to the distance. In other words, the further surface of the screen being heated becomes a new calorific source whose intensity of radiation must decrease as the distance increases.

We possess, therefore, a very simple contrivance for destroying the influence of conduction, if we keep the action of the free radiation intact. This contrivance consists in removing the screen so far from the thermoscope that the radiation of its own heat may, on account of its extreme feebleness, be totally disregarded.

There are, however, some precautions to be taken; for in proportion as the distance between the screen and the thermoscope is increased, the distance between the source and the screen is diminished. The latter is therefore more heated, and radiates with greater force upon the instrument. It is easy to show by calculation that we always gain; that is, that we always weaken the conductible caloric more and more by removing the screen from the thermoscope, until we have placed it midway between the thermoscope and the source. Let us, therefore, put the screen in this position (which is the most favourable of all), and we shall see that its heat has then no appretiable influence on the re obtained by means of the thermomultiplier, and a source whose radiation is much weakened by distance.

The apparatus is disposed in the following manner. A thermoelectric pile of thirty pairs is closed at one end and enveloped, at the other, in a small tube blackened inside to prevent reflection. At a certain distance there is placed a large metallic diaphragm, with an aperture at the centre equal to the section of the pile. On the other side, in the same line, there is a lighted lamp, which is brought more or less close, until the needle which serves as the index of the galvanometer, marks an elevation of 30°. The radiation is afterwards intercepted by a screen of polished metal placed between the lamp and the diaphragm, and the needle returns to zero. Then there is placed on the other side of the diaphragm a stand, with a plate of glass fixed on it, and the whole apparatus is moved gently until it is brought midway between the pile and the calorific source.

This being done, the opake screen is removed; the rays passing through the glass fall on the pile, and immediately cause the galvanometer to move. In 5s or 6s it is driven through an arc of nearly 21°·5, but it afterwards returns nearly to zero, oscillates in an arc of greater or less extent, and at last settles definitively at 21°. This last deviation decidedly marks the whole effect; for it is useless to continue the experiment for 15s or 20s. There is no longer any perceptible movement.

The time which the needle takes to attain its position of steady equilibrium is a minute and a half. When the experiment is repeated with other plates of glass, or of any transparent substance whatsoever, possessing different degrees of thickness, from the hundredth part of a line to five or six inches, the galvanometer exhibits deviations greater or less than 21°; but the time requisite to attain the equilibrium is in all cases the same. In short, if we mark the time which the needle takes to arrive at 30°, we shall find it to be one minute and a half.

The invariability of this time, in such a variety of circumstances, affords the most decisive evidence that the deviations of the galvanometer are exclusively due to that portion of heat which reaches the pile by immediate transmission. Whence it follows, that in the arrangement we have adopted, the heat of the transparent body has no appretiable influence on the instrument.

But a direct proof of this proposition may be obtained by operating on opake screens.

I take a plate of glass a millimetre in thickness. I blacken it on one side, and put it in the place of the transparent plate, taking care to turn its blackened surface to the lamp. The needle remains stationary, although the caloric rays continually fall on the anterior surface. It will be found immoveable also, if we employ a plate of copper coated on both sides with black colouring matter, or a thin flake of wood, or even a sheet of paper. Thus, though we should suppose the screen to be diaphanous, exceedingly thin, an excellent conductor of caloric, and possessing great powers of absorption and emission, the utmost elevation of temperature that can be acquired during the experiment would not furnish rays sufficiently strong to move the index of the galvanometer.

One is surprised at first to see caloric rays capable of giving a deviation of 30° fail to produce any effect when they are absorbed by the screen, which must necessarily send its acquired heat upon the apparatus. But our surprise ceases when we reflect that this heat is sent equally in all directions by every point of the heated screen, and therefore that the portion of total radiation which reaches the apparatus is but a very small fraction.

We shall see hereafter, that the anterior surface of the pile does not measure six square centimetres. With these data, if we suppose even that the thirty degrees of heat are completely absorbed by the screen, and afterwards dispersed through space, we find that the quantity of the rays which reach the thermoscopic body does not amount to the six-hundredth part of the whole. But the galvanometer that I use is capable, at the most, of marking only the 150th part of the force which moves the needle to 30°. Thus, even though the instrument were capable of discovering the presence of a heat four times as feeble, there would be no perceptible action.

The experiments which I have been describing seem to me to leave no doubt whatsoever as to the truth of the proposition just now enunciated; namely, that in my mode of operating the deviation of the galvanometer proceeds entirely from the heat instantaneously transmitted through the screen. These proofs, though so conclusive to my mind, seem however not to have been equally convincing to others; for I have heard some persons say, "We grant that the deviation of 21° obtained through the screen does not arise from the caloric propagated by conduction from the anterior to the other surface, but it may be maintained that it is caused by a heat instantaneously diffused, in the same manner as light, over all the points of the glass." Before we admit such a mode of transmission, it seems to me that we ought to demonstrate its existence by some decisive experiment. But supposing it true, then we must also suppose one of these two things,—either that the molecules of the glass acquire from the action of the source such modifications that they themselves become so many calorific centres, and return to their natural state when the radiation is stopped; or that the heat, which is supposed to be diffused through the material points of the screen, is but common caloric obeying the known laws of equilibrium. In the first case we should be only attempting to explain the very cause of the transmission, and the hypothesis, true or false, does not at all invalidate the fact which we are desirous to establish. In the second case, this heat, when it has reached the interior of the body, must take some time to issue from it; besides, this time must vary with the thickness of the screen, and its powers of conduction and emission. But let us intercept the calorific communication in our apparatus; let us remove the diaphanous screen from its stand, and expose it for some moments to the free radiation of the lamp on the other side of the diaphragm: if the supposition be true, the internal molecules of the glass will instantaneously acquire some heat. In order to see whether this heat really exists, let us replace the screen on its stand before the pile, still leaving the calorific communication with the lamp intercepted. The further surface of the plate of glass will, according to the hypothesis, immediately begin to emit towards the pile that caloric which reaches it successively from within, and the index of the galvanometer must lose its equilibrium. But whatever be the nature or the thickness of the screen with which this experiment is performed, we never obtain the slightest indication of a movement in the magnetic needle. It is therefore completely demonstrated that the deviations of the galvanometer exhibited in the experiments made with the diaphanous screens are not to be attributed, in the least degree, either to the external or the internal heat of the screen itself, but solely and exclusively to free transmission. Thus, whenever, in consequence of the radiant heat of the source being made to fall on a screen, a deviation of the galvanometer is perceptible, we may rest assured that the whole of the effect produced is to be ascribed to the rays of heat immediately transmitted through it, in the same manner as luminous rays.

Before I conclude these preliminary considerations, it is necessary to remark, 1st, that galvanometers of very great sensibility, such as must be used for the thermomultiplier, do not directly indicate quantities less than half-degrees; 2ndly, that the ratios of the degrees of the galvanometer and the forces of deviation are unknown. But it is often useful to have the fractions below the half-degree, and in certain circumstances it is absolutely indispensable to know the ratios of the several degrees of calorific action which move the magnetic needles to different distances from their primitive position.

To find the fractions sought, we have only to take the means of a certain number of observations. As to the ratio of the deviations and the forces, it is difficult and, in the present state of the science, perhaps impossible to determine it generally. But electric piles, such as those employed in the construction of the thermomultiplier, furnish sufficiently simple means of solving the question in each particular case. Indeed there is nothing easier than to keep the index of the galvanometer at any degree of deviation. All that is required for this purpose is to place a lighted lamp at proper distance from either side of the thermoelectrical pile. To prevent the possibility of mistake on this point, let us suppose the axis of the pile to be perpendicular to the magnetic meridian, and the communications so fully established that, when the left or the right side of the pile is heated, a corresponding deviation will be exhibited by the galvanometer. Let there be now produced a sufficiently marked deviation by placing a lamp near enough at the same side. Let this deviation be 44°. After having brought the needle back to 0° by interposing a metallic screen, let us make it move to the 42nd degree of deviation on the left, by means of a second lamp placed on the other side. To bring the needle back again to the zero point of the scale, we have only to stop the radiation by means of a metallic screen, as before.