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has been associated in his mind, from his earliest youth, with every privilege which attaches him to his country, and to his government.

"Indictments have been prepared against six persons; the first is an officer of an Arab ship, who is a native of Mocha, in Arabia, and a person, who, from the number of voyages he has performed, is well known in all the different ports of Madagascar, and of the eastern coast of Africa. The second is a Malay priest, who is an inhabitant of Malacca, and was proceeding from Malacca to Mecca on a pilgrimage, when he was detained at Galle. The third, is a Lascar, who is a native of the Malabar coast, and very well known at all the ports on that coast. The fourth and fifth, are both Lebbes, who are inhabitants of Galle, and belong to that active class of trading Mahometans which is found in every part of the coast of Ceylon. The sixth, is a burgher, who is also an inhabitant of Galle, and who seems to have had considerable intercourse with the foreign ships which are frequently touching at that port.

"Three of the prisoners, as you will perceive, are foreigners, and three of them are British subjects; as the three first were within the British settlements on this island at the time they are charged with having committed the offence, they are as liable as the three last to be tried for the offence, the act under which they are to be tried being applicable not only to British subjects, but also to persons residing, or being within a British settlement at the time they commit

the offence.

"The description of the different prisoners, their respective places of residence, the particular classes of people to which they belong, the impression which the detention, though short, of the Arab ship, is likely to produce at Mocha and at Malacca, the regular intercourse which subsists between Mocha and the coast of Africa on the one hand, and between Malacca and the Eastern Islands on the other, the number of slaves with which that coast and those islands have for ages supplied the different parts of Asia, the lively interest which the people of that coast, and of those islands, must of course take in the subject, are all circumstances which must give the most extensive publicity to the proceedings of this session, and it is with a view to these circumstances, we are bound to conclude that, whatever may be the result of the trials, the proceedings themselves must inevitably be attended with the most important effects, and must be considered as a solemn promulgation made from this place to the

people of Asia and Africa, of those exalted principles of humanity which have actuated the conduct of the British Legislature on the present occasion, and which must, sooner or latter, be productive of the most beneficial consequences to the civilization and happiness of a very great portion of the human race."


In the first Number of a Quarterly Journal of the Royal Institution of Great Britain, lately issued from the press, among other scientific and useful articles is the following from the pen of Mr. Knight, “On the means of giving a fine edge to Razors."

"The machinery consists of a cylindrical bar of cast steel, three inches long without its handle, and about one-third of an inch in diameter. It is rendered as smooth as it can readily be made with sand, or, more properly, glass-paper, applied longitudinally; and it is then made perfectly hard. Before it is used it must be well cleaned, but not brightly polished, and its surface must be smeared over with a mixture of oil and the charcoal of wheat straw, which necessarily contains much siliceous earth in a very finely reduced state. I have some

times used the charcoal of the leaves of the Elymus arenarius, and other marsh grasses; and some of these may probably afford a more active and (for some purposes) a better material; but upon this point I do not feel myself prepared to speak with decision. In setting a razor, it is my practice to bring its edge (which must not have been previously rounded by the operation of a strop) into contact with the surface of the bar at a greater or less, but always at a very acute angle, by raising the back of the razor more or less, proportionate to the strength which I wish to give to the edge; and I move the razor in a succession of small circles from heel to point, and back again, without any more pressure than the weight of the blade gives, till my object is attained. If the razor have been properly ground and prepared, a very fine edge will be given in a few seconds; and it may be renewed again, during a very long period, wholly by the same means. I have had the same razor, by way of experiment, in constant use during more than two years and a half, and no visible portion of its metal has within that period been worn away, though the edge has remained as fine as I conceive possible; and I have never, at any one time, spent a quarter of a minute in setting it."



THE question, what is caloric; or, as it was formerly called, heat? has puzzled philosophers and chemists, from the earliest ages to the present day. Theories have been promulgated in abundance, but a satisfactory solution of the problem has never been given. By some, caloric is thought to be an existent material fluid, of such tenuity and imponderability, as to escape the minutest observation, and only to become manifest by its effects on other bodies. Others suppose, that caloric is not material, but is a property, or principle, of motion, which, by exciting a certain species of vibration among the particles of bodies, causes the sensation and effects of heat.

The first hypothesis, which considers caloric as a substance of extreme tenuity, great elasticity, imponderable, and invisible, is said to have been proposed by Boerhaave. It was advocated by Hamberg and Lemery, and it may be considered the favourite system of chemists in the present day.

The chief arguments in favour of this hypothesis are, that as the addition of caloric to most bodies produces their expansion, it is most natural to suppose, that this effect is owing to the actual insertion of a material substance between the various particles of which the bodies may be composed. The transfer of measured quantities of caloric to effect given purposes of expansion, fusion, vaporisation, or the contrary, is another strong argument on this side the question. The passage of caloric through a vacuum, is also advanced, on the same side; because it is not possible to conceive how, if heat be a property of matter, it should be freely propagated where no matter exists. The experiments of Herschel and others, which tend to prove the distinct separation of heat from light, and that the laws which they obey are analogous, though not identical, have been brought forward in favour of the material hypothesis, as proving the materiality of heat equally with that of light. The second opinion, or, what is called the vibratory hypothesis, i. e. that heat is merely a property of matter, and that it may arise from the vibrations of the molicules, or minute particles, of which matter is composed, is attributed to Bacon, and is thus explained in his own words:" Calor est motus expansivus, cohibitus, et nitens per partes minores:" Heat is an expansive motion, confined and active in its smallest particles. The chief supporters of the vibratory hypothesis were Boyle and Newton formerly; and latterly, Count Rumford, Professor Leslie, and Sir Humphrey Davy. 2D. SERIES, NO. 6.-VOL. I.


The arguments against the materiality of caloric are, that the most careful experiments, made for the purpose, never could prove it to be ponderable; it therefore does not seem to possess the ordinary sensible properties of matter-weight, and obedience to the laws of mechanical motion: also, from the experiments of Count Rumford, it seems that friction is an inexhaustible source of heat in the same given substance.

The following is Sir Humphrey Davy's opinion in his own words :-

"The immediate cause of the phenomenon of heat, is motion; and the laws of its communication are precisely the same as the laws of the communication of motion. Since all matter may be made to fill a smaller volume by cooling, it is evident that the particles of matter must have space between them; and since every body can communicate the power of expansion to a body of a lower temperature; that is, can give an expansive motion to its particles; it is a probable inference, that its own particles are possessed of motion; but as there is no change in the position of its parts, as long as its temperature is uniform, the motion, if it exist, must be a vibratory or undulatory motion, or a motion of the particles round their axes, or a motion of particles round each other.

"It seems possible to account for all the phenomena of heat, if it be supposed that in solids the particles are in a constant state of vibratory motion, the particles of the hottest bodies moving with the greatest velocity, and through the greatest space; that in liquids and elastic fluids, besides the vibratory motion, which must be conceived greatest in the last, the particles have a motion round their own axes, with different velocities, the particles of elastic fluids moving with the greatest quickness; and that, in ethereal substances, the particles move round their own axes, and separate from each other, penetrating in right lines through space. Temperature may be conceived to depend upon the velocities of the vibrations; increase of capacity, on the motion being performed in greater space; and the diminution of temperature, during the conversion of solids into fluids or gases, may be explained on the idea of the loss of vibratory motion, in consequence of the revolution of particles round their axes, at the moment when the body becomes liquid, or aeriform; or from the loss of rapidity of vibration, in consequence of the motion of the particles through greater space."

As advocates for each of these theories, there will be found some of the most distinguished names, that have ever done honour

2 L

149.-VOL. III.

to the intellect of man; but, after all, their speculations have produced little that is convincing to others, or even satisfactory to themselves. A short abstract of the principal facts which have resulted from the experiments tried by philosophers advocating both theories, will be submitted to the reader, and he may judge for himself which system seems most likely to explain the various phenomena.

It is a general fact, that all substances experience an enlargement of their volume by an increase of temperature. The apparent exceptions to this law, can scarcely be considered such as to destroy its generality, though they present irregularities in its application, which it would be injudicious to overlook. Such is the contraction of water, by an increase of temperature below 40° of Fahrenheit. The expansion of some metals at the instant of congelation after fusion, is probably owing to a tendency of their particles to arrange themselves in a crystalline form. In solids this enlargement of bulk is not so great as in liquids, but it is the most conspicuous in the aeriform fluids, or gases; and it appears that the greater the absolute dilatation, the less is the force with which it takes place. For instance, the dilatation of the gases may be overcome by the confinement of strong vessels; but in the case of liquids, or solids, the force of this power seems almost irresistible. The strongest rocks are rent by the expansive force of water freezing in their fissures; and strong cannon have been burst in a similar manner, by water confined within them.

The actual expansive force of solids in the process of heating, has not been made the subject of any thing like admeasurement; but a very curious application of the force exerted in the converse operation of cooling, was made a few years ago, in Paris, by M. Molard. It was discovered, that the side walls of a large room filled with engines, at the Conservatoire des Arts and Métiers, were bulging outwards, from the great internal pressure. To remedy this, strong bars of iron were passed quite through the building; the extremity of each bar passing through the main outer wall. The ends of the bars were formed into screws, and fitted with nuts, which, being screwed up closely to the wall, might have served to prevent further mischief. Still, however, the walls had to be brought into their original position, to effect a complete cure; this was accomplished by heating each bar, a row of lamps being placed beneath it, for the purpose; the heat of the lamps having produced a considerable

elongation of the bars, during this expanded state of the metal, the nuts were screwed up close to the wall again, and, upon the removal of the lamps, the contraction of the bars actually brought together the walls of the building. The operation was repeated upon alternate bars, till the walls had been restored to their true vertical position.

It is well known, that provision must be made for the expansion or contraction consequent upon a change of temperature, in the construction of iron bridges, and the pipes which are placed under ground for the conveyance of water or gas. Where the lengths of the pipes are very considerable, it is necessary to have some points moveable; so that, by the end of one tube sliding a little within the other, the accidental changes, induced by an excess or diminution of caloric, are provided for. In measuring the base of a trigonometrical survey, the utmost care is taken to allow for the contractions and expansions of the metallic rods employed, as a slight change of temperature has been productive of very serious mistakes in the admeasurements. The effects of caloric upon the pendulum are well known.

It has been considered as a universal law of nature, that, by a sufficient elevation of temperature, every substance which is originally solid, might be reduced to a fluid state. It is true, that in practice we fall short of this result, partly because the heat which we can produce by artificial means is of very limited extent, and partly from other properties in the constitution of bodies, which interfere with such a consequence. It has, however, been found that every increase which has been made in our powers for the excitement of intense heat, whether by the Voltaic pile, or the gas blow-pipe, has placed various substances in succession, under the operation of this law, which before formed practical exceptions to it, and an absolutely infusible body now is scarcely known to exist. It is true, many substances burn rather than melt, but this depends upon what is called chemical affinity, by which it happens, in some instances, that a new combination is formed, upon the subversion of the original one.

In some cases, the passage of a solid into the fluid state, upon the application of caloric, is made immediately, without any intermediate process of softening; such is the fusion of ice, frozen mercury, and some of the metals. It has been remarked, that this process chiefly holds good as it regards those bodies, which, in congelation, affect a crystalline structure. Other bodies, on the contrary, seem to change gradually from


solid to liquid, passing through every intermediate degree of cohesion. Arsenic differs from both processes, this metal, when heated, passing at once from a solid to a gaseous state. It still seems an established fact, that the temperature of fluidity is constant for each individual substance.

The complete explanation of the state of fluidity, with reference to the general physical laws of matter, is not so easy a task as might at first be supposed. It has long been stated, that fluidity depends upon the effect of caloric, which first expands bodies, that is to say, removes their integrant particles, or atoms, to a greater distance from each other, until at length, the power of cohesion being overcome, perfect mobility among the particles brings the substance under the laws and definition of a fluid. But this mode of explaining the action of caloric, will not apply in all cases, for it does not account for the fact, that many crystalline solids actually contract in the process of fusion, which is quite contrary to the hypothesis.

Professor Robison remarks, that "to explain the mobility of a fluid, or the facility with which its parts are separated, it is necessary to suppose only, that the action of its particles, whatever it may be, is equal in every direction at the same distance; as, if this equality exist, no force can be required to move an adjacent particle from one situation to another; nor any force be required, to keep the particle in its new situation with regard to the rest of the fluid. And still the attraction exerted between the particles, provided it be equal, may be strong. On the other hand, in a solid, the particles must attract more strongly in one direction than in another; hence a particular situation of each particle must be assumed, and a force, more or less great, will be requisite to change its position. It follows from this view, that fluidity arises not merely from the weakness of cohesion between the particles, but also from the change in the mode in which they attract each other. But this, at the same time, arises from the expansive energy of caloric, which, in separating the particles to certain distances, gives rise to this change in their mutual action; whence they assume different positions, and attract with a different but equal force. It is probable that this depends on the modification introduced by the figure of the particles of bodies. Within a certain distance this must operate on the strength of the attraction they exert; and they will be retained in a certain position rather than in others. But when, by the repulsive agency of caloric, they are placed


at greater distances, this will cease to operate; any effect from figure must be insensible, and the particles will attract equally in all directions-the circumstance which constitutes the liquid form."

By the application of heat, a very considerable number of bodies, both solid and liquid, may be converted into the form of gaseous matter; and as long as a sufficient elevation of temperature continues, the form of an elastic fluid is retained. It is clearly proved, that in this state they are liquids in combination with caloric, for, on violent condensation, they give out a great degree of heat. The only one of the gaseous fluids which has been liquified by cold alone, is ammoniacal gas, which assumes the liquid form at 54° of Fahrenheit. Mr. Faraday has recently shewn, that, by disengaging several of the gases from their state of combination, under such a pressure that the elastic form could never be assumed, they might be exhibited as liquids. As by the increase of temperature all bodies may be melted, and, by a further accession of temperature, pass to the state of an elastic fluid; so, on the contrary, there is reason to believe that, by a sufficient depression of temperature, all those bodies which we know now in a gaseous or liquid state, might be reduced to a solid form. Many philosophers suppose that congelation, or solidity, is the natural state of all substances.

Though great doubt exists relative to the substance of caloric, it is evident that there are three natural sources from whence it may be derived, i. e. the sun, electricity, and mechanical action.

The sun is the most obvious and unvarying source from whence heat is communicated to our earth. The solar rays have lately been discovered to possess four distinct powers, i. e. of heating, illuminating, effecting chemical changes, and exciting magnetism; and, it is now generally supposed, that the rays affording light and heat are entirely different, though so intimately blended as to obey the same optical laws. The experiments of Sir W. Herschel on the heating power of the several prismatic rays, showed satisfactorily, that the more refrangible rays possess very little heating power, the calorific effect being at its maximum in the extreme red rays.

It is well known, that when transparent bodies are exposed to the light of the sun, that the heating effect is greatly inferior to that which is produced upon opake substances. Opake bodies, which all equally resist the passage of light, are not equally affected in temperature by its incidence upon them. The power of absorbing caloric

from the sun's rays, depends in a great measure upon the colour. This was made the subject of experiment by Hooke, Franklin, and, more recently, by Sir Humphry Davy.

Dr. Franklin placed some square pieces of cloth of different colours upon a surface of snow, and noted those as the best absorbers of caloric, which sunk most deeply by melting the snow. Sir H. Davy exposed to the sun, one side of six copper plates, which had been painted of different colours. To the opposite side of each plate, he affixed a bit of cerate, which melted at a temperature of 70° of Fahrenheit. The wax melted on the coloured plates in the following order;-first, black; then blue, green, red, yellow; and, lastly, on the white.

The same colours, exposed to artificial heat, present the same results. Cavallo

found that a thermometer with a blackened bulb stood higher than one with its bulb not blackened, whether exposed to the sun's rays, the light of day, or the light of a lamp. M. Pictet also found that two thermometers, one blackened, the other not, manifested the same temperature in the dark. Such are the effects of the beams of the sun in their ordinary state, but when condensed by being collected in the focus of a concave metallic speculum, their force is irresistible, and only to be excelled by the powers of the Voltaic pile: the most refractory substances become fused, while the more volatile dissolve in the fervent heat. Count Rumford endeavoured to prove, by a course of experiments, that this great increase of power is not the effect of any change in property, from the altered direction of the rays, by thus concentrating them into a focus, but is solely due to the intensity of action, arising from the accumulation of numbers, thus brought to bear on the same point.

It has long been known that electricity is one grand source of caloric, but Dr. Franklin was the first who fused metals by the electric spark. His method was, to place small strips of metal between two plates of glass firmly tied together, and then put them within the circuit of the electrical discharge from a jar or battery. In this experiment the glass is frequently broken, and a partial fusion of both substances takes place. Franklin found that a piece of gold leaf, which he had made use of in this way, resisted the action of nitro-muriatic acid, from the circumstance of its being imbedded in the glass.

One strong fact in favour of the mate. riality of caloric, as derived from electricity,

is as follows.—If a charge from a large jar be passed through a small wire, such a degree of heat is evolved, as to produce the ignition of the wire. In this phenomenon the sudden transit of the electric fluid is the primary cause: now, if what is termed electricity, which is allowed to be a modification of caloric, be in reality a substantial fluid, it would be consistent with observed analogies, that when a considerable mass of this eminently expansible fluid, is forced through a very small channel, and thereby greatly condensed, heat and light should be evolved.

The effects of gradually increasing the power of the charge, when wires of the same length and diameter are employed, are very remarkable. If the wire be iron or steel, its colour is first changed to yellow, then (by an increased charge) to blue; by a further increase it becomes red-hot, then fused into balls, which disperse in a shower of globules, and, lastly, disappears with a bright flash, producing an apparent smoke, which, if collected, proves to be a very fine powder, weighing more than the metal employed, and consisting of it, and a portion of the oxygen of the atmosphere with which it has combined.

The experiments of Mr. Cavallo have shewn that the electric fluid differs in its action upon metals from the common fire, and that they are thus distinct substances. He likewise discovered, in fusing the grains of native platinum by the electric spark, that the largest grains were the easiest acted upon, being agglutinated together by a moderate shock, while the small greycoloured dust was so refractory as not to shew any signs of fusion, even when examined by the microscope. This remarkable fact has been explained by the discoveries of Dr. Wollaston, that the small grey particles, found mixed with those of the native platinum, are in reality different metals, much less capable of fusion, and now known by the names of rhodium, osmium, and iridium. It has been found by various experiments, that electricity accelerates the transmission of caloric in a remarkable degree; and that metals heated to incandescence by electricity, continue to evolve light longer than if heated by a common fire, other circumstances remaining the


There are nominally three modes of mechanical action, by which heat is developed,-percussion, condensation, and


If a piece of iron he struck with a hammer, the metal acquires a sensible elevation of temperature, and by repeated blows it

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