THERE have been lately exhibited in London, in various of the clockmakers' and jewellers' shops, models of ships put in action by annexed machinery, and having the various rolling and pitching motions which naturally occur with real vessels. It is one

of the most successful attempts at imitative motion ever accomplished. It is perfectly free from all those staccato effects which generally mar the finest productions of clock-work, and it faithfully exhibits the easy, ever-varying, and ever-blending changes of position and surface, which a steady stiff breeze will produce on a flowing sea, and a vessel under full sail.

The sympathy, if we may so term it, of the ship with the sea, is admirable; when she seems to overtake a wave, her bow slides up its side, and is projected into the air; as she rides on its breast, her

stern also becomes elevated, and her deck is, for an instant, horizontal; and then, as she leaves it, her bow is depressed, and she sinks bodily down into the succeeding hollow.

Though the effects are so perfect, yet the mechanism, it will be evident, is very simple. It is concealed in the model from the observer, by a membrane, which is attached to the hull, and thence extending to the borders of the machinery-chest, is there fastened. This membrane is very delicate in its texture, and extremely pliant; it is not strained tight, but, on the contrary, left very full; and its surface is painted to represent an agitated sea. In all the elevations and depressions of the vessel, this membrane of course accompanies it; but to the spectator, the motions of the vessel seem to be the effect and not the cause of the waves.

In the diagram, one of the containing plates of the machinery is removed to show the connexion of the parts. A spring contained in a barrel A communicates motion to the wheel B, by means of the pinion in the centre of it; this works the wheel C, which is connected with and turns the wheel D; the wheels C and D having the same number of teeth. The force is continued onward to the scapement wheel F, which, working into an endless screw attached to a fly, serves the purpose of equalizing the movement, preventing the machinery suddenly running down; it answers, however, no object in communicating either of the motions of the vessel itself. This is accomplished by means of levers attached to cranks working from the centres of the wheels C and D; the other end of those levers being attached to the side of the vessel at two points, as represented underneath the membrane. Also to the same part, or still better to the keel, is attached the bent lever F, resting on a fulcrum I, which is continued beyond to any convenient length, and has near its end a moveable wheel attached.

Supposing the lever F to be removed, the cranks and the levers vertical, and the machinery in action, it will be seen by examination, that motion would be communicated to the vessel, but that it would be simply vertical, a mere up and down movement, and that the deck would be always parallel to the line in which it lay at starting; if we add the lever F, centering it midway between the points where the levers from the wheels are fastened to the side of the vessel, a very small but scarcely perceptible variation would be produced, but if we now place its centre-pin nearer to the centre-pin of one of the shafts than to that of the other, we shall have the motion of the two levers so controlled by the lever F, that they move both ascending and descending, with different and differing velocities; so that the stem and the stern of the ship will rarely remain for two successive instants in the same level plane.

The invention is French, and patented. The names of T. C. Cailly and Eude, are stamped upon the machinery case.

THE CLOCK PENDULUM.

Ir is controverted by Galileo and Huygens which of the two first applied the pendulum to a clock.

After Huygens had discovered that the vibration made in arcs of a cycloid, however unequal they might be in extent, were all equal in time, he soon perceived that a pendulum applied to a clock, so as to make it describe arcs of a cycloid, would rectify the otherwise unavoidable irregularities of the motion of the clock; since, though the several causes of these irregularities should occasion the pendulum to make greater or smaller vibrations, yet, by virtue of the cycloid, it would still make them perfectly equal in point of time: and the motion of the clock governed by it would, therefore, be preserved in equal regularity. But the difficulty was, how to make the pendulum describe arcs of a cycloid; for naturally the pendulum, being tied to a fixed point, can only describe regular arcs about it.

Here Huygens contrived to fix the iron rod or wire, which bears the ball or weight at the top, to a silken thread, placed between two cycloidal cheeks, or two little arcs of a cycloid, made of metal.

Hence the motion of vibration, applying successively from one of those arcs to the other, the thread, which is extremely flexible, easily assumes the figures of them, and by that means causes the ball or weight at the bottom to describe a just cycloidal arc.

This is, doubtless, one of the most ingenious and useful inventions many ages have produced, by means of which it has been asserted, that there have been clocks which would not vary a single second in several days; and the same invention also, gave rise to the whole doctrine of involute and evolute curves, with the radus and degree of curvature, &c.

It is true the pendulum is still liable to its irregularities, how minute soever they may be. The silken thread by which it is suspended shortens in moist weather, and lengthens in dry, by which means the length of the whole pendulum, and consequently the times of the vibrations, are somewhat varied.

To obviate this inconvenience, M. de la Hire, instead of a silken thread, used a fine spring, which was not indeed subject to shorten or lengthen from those causes; yet he found it grew stiffer in cold weather, and then made its vibrations faster than in warm, to which also we may add its expansion and contraction by heat and cold. He, therefore, had recourse to a stiff wire or rod, from one end to the other. Indeed by this substitute he renounced the advantages of the cycloid; but he found, as he says, by experience, the vibrations in circular arcs are performed in times as equal, provided they are not of too great extent, as those in cycloids; but the experiments of Sir Jonas Moore, and others, have demonstrated the contrary.

The ordinary causes of the irregularities of pendulums; Dr. Durham ascribes to the alterations in the gravity and temperature of the air, which increase and diminish the weight of the ball, and by those means make the vibration greater and less; an accession of weight in the ball being found by experiment to accelerate the motion of the pendulum, for a weight of six pounds added to the ball, Dr. Durham found, made his clock gain three seconds every day.

A general remedy against the inconveniences of pendulums is to make them long, the ball heavy, and to vibrate but in small arcs. These are the usual means employed in England; the cycloidal cheeks being generally neglected.

Pendulum clocks, resting against the same rail, have been found to influence each other's motion. R. J. T. B.

ANIMAL HEAT.

THE natural temperature of man is so constant and equable, that a thermometer bulb being placed under the tongue, the mercury will be found to stand at nearly the same degree (96°) in the hottest climate, as at the poles. This heat is very little dependent upon external circumstances, and the investigation of its origin is worthy the attention of the scientific. For the first consistent theory of the production of animal heat we are indebted to Dr. Crawford. He considered that arterial blood has a greater capacity for heat than venous blood, and common air than carbonic acid gas. To make his theory intelligible, I should premise that the circulation of the blood is performed in

the following manner :-The blood is propelled from the heart into the arteries-it is distributed throughout the body and returns again to the heart through the veins in respiration a remarkable change takes place through the medium of the air in the lungs ; the black venous blood being exposed to the air is converted into florid arterial blood; a certain proportion of oxygen is withdrawn from the air, and a corresponding volume of carbonic acid gas eliminated; such is the process of the circulation and sanguification of the blood, and on this was Crawford's theory founded. When the carbon of the venous blood unites with the inspired oxygen, and forms carbonic acid, the less capacity of this than common air for caloric, must cause an increase of temperature; but the blood, having changed from venous to arterial, has acquired a greater capacity than before, and absorbs the heat given out by the carbonic acid. The blood, of course, does not become warmer; because the amount of heat is no more than enough to render its temperature equal to what it was before. The body in this way acquires a fund of caloric, and yet the lungs, the laboratory in which it is acquired, do not experience any elevation of temperature.

Another and very different hypothesis has been advanced by that illustrious physiologist, Sir Benjamin Brodie. He refers the generation of animal heat solely to the nervous system. He divided the spinal marrow of many of the inferior animals, and at the same time kept up respiration by artificial means; but though the sanguification of the blood was effected, though carbonic acid was duly eliminated, the temperature of the animals rapidly ell. He therefore concludes, that animal heat depends much more upon the influence of the nerves, than any chemical changes occurring in respiration.

Such are the most plausible theories yet advanced to account for the subject under our notice; let me now examine their comparative merits. The hypothesis of Crawford is untenable in its full extent, for recent investigations have shown that there is no difference, in capacity for heat, between venous and arterial blood; consequently the corner-stone of this theory is shaken. Again, the experiments of Brodie are not beyond cavil, for other physiologists assert, that animal heat may be maintained for some time by the aid of artificial respiration, even when all connection has ceased between the brain and lungs. Such is the position in which the matter at present rests; there is a vital and chemical hypothesis. I am inclined to think that a modification of Crawford's views may be adopted with much plausibility; it is going too far to say, that the arterialization of the blood has nothing to do with the maintenance of the vital temperature-one of the great functions performed by respiration is the evolution of much carbonic acid from the system; now we know, that the disengagement of carbonic acid is often, or I may say always, accompanied by evolution of caloric-such as in combustion and fermentation, and to say the least of it, there is a remarkable parallelism between combustion and respiration. Warm-blooded animals are observed to consume the most oxygen, and in proportion as their respiration is perfect, are they found to possess the most animal heat. Thus reptiles and fishes are very little warmer than the elements they inhabit.

W. PRESTON.

[Our correspondent is, perhaps, not aware of

the recently-promulgated theory of Dr. J. M. Winn, (see Philosophical Magazine, March, 1839,) who has gone far to prove that the incessant contractions and dilatations of the arteries during life must prove an efficient source of animal heat. The Dr. was led to this inference by having observed that caoutchouc has the property of evolving heat when suddenly stretched. To prove the accuracy of his supposition, that other bodies might be endowed with a similar property, he took the aorta of a bullock, and was gratified in being enabled to verify his previous conjecture. The experiment he describes as follows:-" Having cut off a circular portion of the descending arc of the aorta, about an inch in length, I laid it open, and carefully dissected out the elastic coat, and taking hold of it by each extremity I pulled it to and fro with a continuous jirking motion, (in imitation of the systole and diastole of the artery,) for the space of about a minute. When, placing it upon the bulb of a thermometer, I had the satisfaction to find that after it had remained two minutes, the mercury had risen as many degrees. On removing the thermometer, the heat immediately began to diminish." The Dr. took every precaution to prevent the heat arising from his hand, breath, &c., and concludes that the whole of the heat developed in the animal economy can, by this theory, be satisfactorily explained, and also that the variations of animal temperature, arising from topical inflammations, exercise, the chemical functions of the viscera, febrile disorders, and decrease of animal heat in old age, can be more readily accounted for by this mechanical theory, than by either that of Dr. Crawford, or Sir B. Brodie.-ED.]

NATURE OF PETRIFACTION.

In many instances we find a mere substitution of mineral matter for the original animal or vegetable substance. Such are those casts of sandstone, indurated clay, and other consolidated materials, which bear the forms and impressions of organic bodies, but possess neither the internal structure, nor any vestige of the constituent substances of the original. Casts and impressions of shells, of the stems and leaves of plants, and of fish-scales; the flints, which derive their form from echinites, &c., are familiar examples of this process.

In genuine petrifactions a transmutation of the parts of an organized body into mineral matter takes place. Patrin, Brongniart, and other philosophers, suppose that petrifaction has frequently been effected suddenly, by the combination of gaseous fluids with the constituent principles of organic structure. It appears, indeed, certain, that the conversion into silex both of animal and vegetable substances, must, in the majority of instances have been almost instantaneous, for the most delicate parts, those which would undergo decomposition with great rapidity are often preserved; such, for instance, as the capsule of the eye, the membranes of the stomach, the soft bodies of molusca; and in plants, the cellular and vascular tissue, and even the pollen. The fact of the silicification of trees in loose sand, and of the bodies of molusca in their shells, as in the fossil oysters from Brighton, while neither the sand in the one instance, nor the shells in the other, are impregnated with silex, cannot be explained by the infiltration of a siliceous fluid into cavities left by the decomposition and removal of the animal

substance. A combination of gaseous fluids, with the constituent principles of the animal or vegetable, changing the latter into stone, without modifying the arrangement of their molecules, so as to alter forms, seems the only mode by which such a transmutation can have been effected. The production of congelation, by a simple abstraction of caloric, is akin to this change; but petrifaction is induced by the introduction of another principle. As to density, the most subtle gaseous fluids may acquire the greatest solidity; as, for example, in the union of oxygen with metallic substances. Oxygen is supposed by Patrin to be a chief agent in the phenomenon of petrifaction, by its combination with the phosphoric principle, which is present in organized bodies.

Artificial Petrifactions.-Last year M. Goppert published the result of an interesting investigation of the condition of fossil plants, and the process of petrifaction. Mr. Parkinson had remarked, that the leaf in ironstone modules might sometimes be separated in the form of a carbonaceous film; and M. Goppert having lately found similar examples, was induced to undertake a set of experiments. *He placed fern leaves in clay, dried them in the shade, exposed them to a red heat, and obtained striking resemblances to fossil plants. According to the degree of heat, the plant was found either brown, shining black, or entirely lost, the impression only remaining; but in the latter case the surrounding clay was stained black, thus indicating that the color of the coal shales is from the carbon derived from the plants they include. Plants soaked in a solution of sulphate of iron were dried and heated till every trace of organic matter had disappeared, and the oxyde was found to present the form of the plant. In a slice of pine-tree the punctured vessels peculiar to this family of vegetables were perceptible. These results by heat are probably produced naturally, by the action of moisture under great pressure, and the influence of a high temperature.

Fossilization of Wood. Sometimes the most minute structure is preserved, as in the vessels of palms and coniferæ, which are as distinct in the fossil as in the recent trees. From this state of perfection, we have every degree of change, to the last stage of decay; the condition of the wood, therefore, had no influence on the process. The hardest wood, and the most tender and succulent, as for instance, the young leaves of the palm, are alike silicified. In some instances, the cellular tissue has been petrified, and the vessels have disappeared; here silicification must have taken place soon after the wood was exposed to the action of moisture, because the cellular structure would soon decay; the process was then suspended, and the vessels decomposed. In other examples, the vessels alone remain; a proof that petrifaction did not commence till the cellular tissue was destroyed. The specimens where both cells and vessels are silicified, show that the process began at an early period, and continued till the whole vegetable structure was transmuted into stone. Dr. Turner, in some admirable comments on the subject of petrifaction, remarks, that whenever the decomposition of an organic body has begun, the elements into which it is resolved are in a condition peculiarly favorable to their entering into new combinations; and that if water, charged with animal matter, come in contact with bodies in this state, a mutual action takes place, new combinations result, and solid

particles are precipitated, so as to occupy the place left vacant by the decomposed organic matter.

Mr. Parkinson, in corroboration of his opinion that wood undergoes bituminization before it becomes petrified, mentions, that a specimen of wood from Walton, which was changed into marble, and took a beautiful polish, left, upon removing the carbonate of lime by muriatic acid, a mass of light, inflammable, bituminous wood, which possessed a volume almost equal to its original state.

Petrifaction by Flint.-The various forms in which silex is found, are proved to have been dependant on its state of solution; in quartz crystals it was entirely dissolved, in agate and chalcedony it was in a gelatinous state, ass

a spheroidal, or orbicular disposition, according to the motion given to its molecules. Its condition was also modified by the influence of organic matter. In some polished slices of flints from Bognor the transition from flint to agate, chalcedony, and crystallized quartz, is beautifully exhibited. The shell of an echinus, in the possession of Dr. Mantell, is transmuted into crystallized carbonate of lime, and the lower part of the cavity occupied by flint, the upper surface of the latter being covered by crystals of calcareous spar. The curious fact that the shells of the echinites in the chalk are almost invariably filled with flint, while the crustaceous covering is converted into calcareous spar, is, perhaps, attributable to the animal matter of the echinus having undergone silicification; for the most organized parts are those which appear to have been most susceptible of siliceous petrifaction. In. another specimen in Dr. Mantell's museum, the body of an oyster is turned into flint, while the shell is, as usual, carbonate of lime. The shells of molusca, the crustaceous skeletons of echini, and the bones of the belemno-sepiæ, appear to have possessed too little animal matter, and to have been too much protected by calcareous earth, to have become silicified; they are changed into spar by water charged with carbonic acid gas, having insensibly effected the crystallization of their molecules.

about fourteen inches, and the versed side, or depth, about five inches, the breadth two inches. At A is fixed a small deep grooved pulley, and at C is another, about one and a half inch in diameter, also deeply grooved: at D is soldered a stout wire, bent as in the figure. E is a small cylinder of brass, with a hole through it in the direction of its axis, a little larger than the size of the wire intended to be covered; the diameter of the aperture may vary according as we may wish to give

a thick or a thin covering to the wire. Several cylinders ought to be made of different bores, to accommodate wire of different sizes. The cylinders have small steel centres, as represented at F, which fit severally into a steel fork or spring. The bottom part of the steel spring fits into a tube at the end of B, where is a channel to convey back into the vessel the redundant resin. The cylinder E, therefore, having motion in every direction, can accommodate itself to the wire. It will, however, always be best to draw the wire from the wax in a line in which C and D coincide. Every thing being now arranged, the wire to be covered is passed over the pulley at A, under C, over D, hrough the brass cylinder at E. The brass cylinder must be heated by means of a lamp, in order to prevent it solidifying the wax. The vessel is now to be partially filled with melted sealing wax or resin, and the wire must be drawn through at a pretty quick, though regular speed. The wax may be kept melted by a lamp placed underneath the vessel. If the wax get solid at E it must be melted by means of the lamp.

With an apparatus like this, 2500 feet of thin wire have been covered in half an hour.

The resin is made by mixing equal parts of shell lac and Venice turpentine, taking care to melt the turpentine before putting in the shell lac, which must be done gradually. If the wax should be found too brittle, it may be brought to a proper consistence by adding a little spirits of turpentine. A few trials will enable a person to judge of the right consistence of the wax.

Wire covered in this way is as valuable for electro-magnetic purposes, as if it were covered with silk or cotton.

PRINTING BY ELECTRICITY

THE production of drawing by electricity is a subject which seems to have engaged more attention abroad than in this country. In Russia they have long been in the practice of engraving what are called Russian snuff-boxes, which are formed of a kind of imitation platinum, and have drawings made upon them by an application to their conducting powers. Recently, Professor Jacobi, of St. Petersburgh, has been encouraged by the Emperor in a course of experiments on copying copper-plates by galvanism. He uses a new compound metal, and transmits all the lines of the engraving with perfect accuracy.

The sympathy and antipathy of electricity to particular colors seem, however, to point out a means of more easily effecting the process of copying. It has long been known that electricity is repelled by a black surface, and attracted by white; and some interesting illustrations of the effects of a thunder-storm upon cattle are related in the "Philosophical Transactions." This effect has been further confirmed by an able article on the operation of lightning on the masts of menof-war, read before the Electrical Society at one of their late meetings.

This property of color might be so applied, as, by electrical power, to produce engraved plates from prints, impressions of prints from plates or even from other prints, and an operation introduced which might, in some cases, compete with photograhy, and in others supersede the printing press.-Railway Magazine.

MELLONI'S EXPERIMENTS ON HEAT. Ar the Royal Institution, on the 23rd of January, 1835, Dr. Faraday commenced the lectures of the season by describing and exhibiting the experiments which Melloni, a young Italian philosopher now resident at Paris, contrived to elucidate the nature of heat.

The great improvement which he has introduced, and which bids fair to enable us soon to develope completely the cause of the phenomenon dependent on the presence of this important principle, is the adaptation of the thermo-multiplier as a delicate indicator of sensible heat. All the experiments which had been previously made on this subject were performed by means of Leslie's differential thermometer, which, although comparatively, as to other instruments, a delicate contrivance, is surpassed in an infinite degree by the thermo-multiplier. The multiplier consists of about 30 pairs of bars of bismuth and antimony; the elements being so extremely delicately formed that the extremities present a surface of 4-10ths of an inch square. These are made to communicate with the multiplier, by means of wires leading from the extreme bars. The multiplier consists of a coil of silver wire, armed with silk, and having a magnetic needle so placed in a free space within the centre of the coil, as to enable it to oscillate readily. Now, it was observed by Melloni, that when heat, even that of the hand, is applied to the pile, a powerful effect is produced upon the needle of the multiplier, which undergoes an immediate declination, and traverses an arc more or less great if the heat is constant in a constant interval. It is quite obvious, therefore, that this must be a most excellent thermoscope, and must be admirably adapted to the delicacy which is necessary in experimenting in reference to heat. Provided, then, with this apparatus, Melloni set about examining accurately the relations of heat and light, a problem which philosophers have long been endeavouring to elucidate. For this purpose, he studied permeability of heat through different bodies. Mariotte concluded, from his experiments, that the heat of a common fire does not pass through glass, or at least, in very minute quantity. Scheele went further, and decided that not a ray of heat traversed glass. Pictet, however, repeated Scheele's experiment, and obtained a contrary result. From these observations, and those of Herschel, it was inferred that heat does not pass through diaphanous substances, with the exception of atmospheric air. Prevost and Delarouche, by ingenious adaptations, proved, however, that heat is transmitted directly through glass, independent of its conducting power; and this fact has been allowed, with few exceptions, by all philosophers. But although this admission was made, the subject was involved in great obscurity, and presented an inviting field of inquiry to the ingenuity of Melloni. No examination had been instituted into the influence of the state of the surface, of the thickness of the substances through which the heat was transmitted, or of their internal structure upon permeating heat. These, however, were taken up by Melloni, and he is still engaged in prosecuting his researches. It is easy to see how the different relative diathermal powers or capacities of bodies for transmitting heat could be determined by the apparatus of Melloni, for all that was required was to interpose the substance