Part 83

SCALIOT'S LOCK, &c.--In the twentieth year of Queen Elizabeth, Mark Scaliot, a blacksmith, made a lock, consisting of eleven pieces of iron, steel, and brass, all which, together with a pipe-key to it, weighed but one grain of gold: he made also a chain of gold, consisting of forty-three links, whereunto having fastened the lock and key before mentioned, he put the chain about a flea's neck, which drew them all with ease. All these together, lock and key, chain and flea, being weighed, the weight of them was but one grain and a half.

PRAXITELES' VENUS.--Praxiteles, who was an ingenious worker in imagery, made a statue of Venus for the Cnidians, so much resembling life, that a certain young man became enamoured of it to such a degree, that the excess of his love deprived him of his senses. This piece of art was so eagerly coveted by king Nicomedes, that, though the Cnidians owed him an immense sum of money, he offered to take the statue in full satisfaction for his debt; but was refused.

The next subject is a curious WEAVING ENGINE.--At Dantzic in Poland, there was set up a rare invention for weaving four or five webs at a time, without any human help. It was an engine that moved of itself, and would work night and day. This invention was suppressed, because it would have ruined the poor people of the town; and the artificer was secretly destroyed, as Lancelotti, the Italian abbot, relates from the mouth of M. Muller, a Pole, who had seen the device.

HYDRAULIC BIRDS.--At Tibur, in Tivoli, near Rome, in the gardens of Hippolitus d'Este, Cardinal of Ferrara, there are the representations of sundry birds sitting on the tops of trees, which, by hydraulic art, and secret conveyances of water through the trunks and branches of the trees, are made to sing and clap their wings; but at the sudden appearance of an owl out of a bush of the same artifice, they immediately become all mute and silent. It was the work of Claudius Gallus, as Possivenus informs us.

HERSCHELL'S GRAND TELESCOPE.--The tube of this telescope is thirty-nine feet four inches in length, and four feet ten inches in diameter, every part being made of iron. It stands in the open air, appears to be considerably elevated, and is encircled with a complicated scaffolding, by which its steadiness is secured. The concave face of its speculum is _forty-eight inches_ of polished surface in diameter, and it weighs nearly _two thousand one hundred and eighteen pounds_! With proper eye-glasses it magnifies above _six thousand times_: it is the largest instrument, and has the greatest magnifying power, of any that has been made. By its aid, Dr. Herschell has been able to observe the lightning in the atmosphere of the moon, and has found out several celestial bodies, unknown to preceding astronomers. The whole was finished on August the 28th, 1789, on which day the _sixth_ satellite of Saturn was discovered. The observer, suspended at the end of the instrument, with his back towards the object he views, looks down the tube, and sees the image reflected from the mirror; whilst a man below turns gently round the instrument, to accord with the apparent rotatory motion of the heavens, thus preserving the image of the object on the mirror with stability.

BOVERICK'S CURIOSITIES.--Mr. Baker, in his Treatise on the Microscope, says, "I myself have seen, near Durham Yard, in the Strand, and have examined with my microscope, a chaise, (made by one Mr. Boverick, a watch-maker,) having four wheels, with all the proper apparatus belonging to them, turning readily on their axles, together with a man sitting in the chaise, all formed of ivory, and drawn along by a flea, without any seeming difficulty. I weighed it with the greatest care I was able; and found the chaise, man, and flea, were barely equal to a single grain. I weighed also, at the same time and place, a brass chain made by the same hand, about two inches long, containing two hundred links, with a hook at one end, and a padlock and key at the other; and found it less than the third part of a grain. I have seen (made by the same artist) a quadrille table with a drawer in it, an eating-table, a sideboard table, a looking-glass, twelve chairs, with skeleton backs, two dozen of plates, six dishes, a dozen knives, and as many forks, twelve spoons, two salts, a frame and castors, together with a gentleman, lady, and footman, all contained in a cherry-stone, and not filling much more than half of it."

BUNZLAU CURIOSITIES.--Mr. Adams, in his Letters on Silesia, gives the following account of two ingenious mechanics he met with at Bunzlau. Their names were Jacob, and Huttig; the one was a carpenter, the other a weaver, and they were next-door neighbours to each other. "The first (says Mr. Adams) has made a machine, in which, by the means of certain clock-work, a number of puppets, about six inches high, are made to move upon a kind of stage, so as to represent in several successive scenes the passion of Jesus Christ. The first exhibits him in the garden at prayer, while the three apostles are sleeping at a distance. In the last, he is shewn dead in the sepulchre, guarded by two Roman soldiers. The intervening scenes represent the treachery of Judas, the examination of Jesus before Caiaphas, the dialogue between Pilate and the Jews concerning him, the denial of Peter, the scourging, and the crucifixion. It is all accompanied by a mournful dirge of music; and the maker, by way of explanation, repeats the passages of Scripture which relate the events he has undertaken to shew. I never saw a stronger proof of the strength of the impression of objects, which are brought immediately home to the senses. I have heard and read more than one eloquent sermon upon the passion; but I confess, none of their most laboured efforts at the pathetic ever touched my heart with one-half the force of this puppet-show. The traitor's kiss, the blow struck by the high-priest's servant, the scourging, the nailing to the cross, the sponge of vinegar, every indignity offered, and every pain inflicted, occasioned a sensation, when thus made perceptible to the eye, which I had never felt at mere description.

"Hultig, the weaver, with an equal, or superior mechanical genius, has applied it in a different manner, and devoted it to geographical, astronomical, and historical pursuits. In the intervals of his leisure from the common weaver's work, which affords him subsistence, he has become a very learned man. The walls of his rooms are covered with maps and drawings of his own, representing, here the course of the Oder, with all the towns and villages through which it runs; there, the mountains of Switzerland, and those of Silesia, over both of which he has travelled in person. In one room he has two very large tables, one raised above the other: on one of them he has ranged all the towns and remarkable places of Germany; and on the other, of all Europe: they are placed according to their respective geographical bearings. The names of the towns are written on a small square piece of paper, and fixed in a slit on the top of a peg, which is stuck into the table. The remarkable mountains are shewn by some pyramidical black stones; and little white pyramids are stationed at all the spots which have been distinguished by any great battle, or other remarkable incident. The man himself, in explaining his work, shews abundance of learning, relative to the ancient names of places, and the former inhabitants of the countries to which he points; and amused us with anecdotes of various kinds, connected with the lands he has marked out.

"Thus, in shewing us the Alps, he pointed to the very spot over which the French army of reserve so lately passed, and where Buonaparte so fortunately escaped being taken by an Austrian officer; and then he gave us a short comment of his own, upon the character and extraordinary good fortune of the First Consul. In a second room he has a large machine, representing the Copernican system of the universe: it is made in such a manner, that the whole firmament of fixed stars moves round our solar system once in every twenty-four hours, and thus always exhibits the stars, in the exact position, relative to our earth, in which they really stand. Internally, he has stationed all the planets which belong to our system, with their several satellites, and all the comets that have been observed during the last three centuries. In a third room he has another machine, exhibiting in different parts the various phases of the moon, and those of Jupiter's satellites, the apparent motion of the sun round the earth, and the real motion of the earth round the sun.

"In his garret he has another work, upon which he is yet occupied, and which, being his last labour, seems to be that in which he takes the most delight. Upon a very large table, similar to that in the first room, he has inlaid a number of thin plates of wood, formed so as to represent a projection of the earth under Mercator's plan. All the intervals between the plates of wood designate that portion of the world which is covered with water. He has used a number of very small ropes of two colours, drawn over the surface in such a manner as to describe the tracks of all the celebrated circumnavigators of the globe. The colours of the ropes distinguish the several voyages which claim especial pre-eminence above the rest. To Columbus, Anson, and Cook, he has shewn a special honour by three little models of ships bearing their names, which are placed upon the surface of his ocean, in some spot of their respective courses. The names of all the other voyagers, and the times at which their voyages were performed, are marked by papers fixed at the points of their departure. Such is the imperfect description I can give you, from a short view of the labours of this really curious man. He must be nearly, or quite seventy years old, and has all his lifetime been of an infirm constitution. But this taste for the sciences, he told us, was hereditary in his family, and had been common to them all, from his great-grandfather down to himself. His dress and appearance were those of a common weaver: but his expressive countenance, at once full of enthusiastic fire and of amiable good-nature, was a model, upon which Lavater might expatiate with exultation. The honest and ingenious weaver, on our taking leave, made us smile by exclaiming, that now, if he could but have a traveller from Africa come to see his works, he could boast of having had visitors from all the four quarters of the globe."

ARTIFICIAL FLYING.--The art of flying has been attempted by several persons in all ages. The Leucadians, out of superstition, are reported to have had a custom of precipitating a man from a high cliff into the sea, first fixing feathers, variously expanded, round his body, in order to break his fall. Friar Bacon, who lived near five hundred years ago, not only affirms the art of flying possible, but assures us, that he himself knew how to make an engine, wherein a man, sitting, might be able to cenvey himself through the air, like a bird; and further adds, that there was one who had then tried it with success: but this method, which consisted of a couple of large thin hollow copper globes, exhausted of the air, and sustaining a person who sat thereon, Dr. Hooke shews to be impracticable. The philosophers of King Charles the Second's reign were mightily busied about this art. Bishop Wilkins was so confident of success in it, that he says, he does not question but, in future ages, it will be as usual to hear a man call for his wings, when he is going a journey, as it is now to call for his boots.

The art of flying has in some measure been brought to bear in the construction and use of balloons.

CHAP. LXXIV.

CURIOSITIES RESPECTING THE ARTS.--(_Concluded._)

_Burning Glasses--Ductility of Glass--Remarkable Ductility and Extensibility of Gold--Pin Making--Needles--Shoes--The Great Bell of Moscow._

BURNING GLASSES.--We have some extraordinary instances and surprising accounts of prodigious effects of burning-glasses. Those made of reflecting mirrors are more powerful than those made with lenses, because the rays from a mirror are reflected all to one point nearly; whereas by a lens, they are refracted to different points, and are therefore not so dense or ardent. The whiter also the metal or substance is, of which the mirror is made, the stronger will be the effect.

The most remarkable burning-glasses, or rather mirrors, among the ancients, were those of Archimedes and Proclus; by the first of which the Roman ships, besieging Syracuse, (according to the testimony of several writers,) and by the other, the navy of Vitalian besieging Byzantium, were reduced to ashes. Among the moderns, the burning mirrors of greatest eminence, are those of Vilette, and Tschirnhausen, and the new complex one of M. de Buffon.

That of M. de Vilette was three feet eleven inches in diameter, and its focal distance was three feet two inches. Its substance is a composition of tin, copper, and tin glass. Some of its effects, as found by Dr. Harris and Dr. Desaguliers, are, that a silver sixpence melted in seven seconds and a half; a king George's halfpenny melted in sixteen seconds, and ran in thirty-four seconds; tin melted in three seconds; and a diamond weighing four grains, lost seven-eighths of its weight. That of M. de Buffon is a polyhedron, six feet broad, and as many high, consisting of one hundred and sixty-eight small mirrors, or flat pieces of looking-glass, each six inches square; by means of which, with the faint rays of the sun in the month of March, he set on fire boards of beechwood at one hundred and fifty feet distance. Besides, his machine has the conveniency of burning downwards, or horizontally, at pleasure; each speculum being moveable, so as, by the means of three screws, to be set to a proper inclination for directing the rays towards any given point; and it turns either in its greater focus, or in any nearer interval, which our common burning-glasses cannot do, their focus being fixed and determined. M. de Buffon, at another time, burnt wood at the distance of two hundred feet. He also melted tin and lead at the distance of above one hundred and twenty feet, and silver at fifty.

Mr. Parker, of Fleet-street, London, was induced, at an expense of upwards of £700, to contrive, and at length to complete, a large transparent lens, that would serve the purpose of fusing and vitrifying such substances as resist the fires of ordinary furnaces, and more especially of applying heat in vacuo, and in other circumstances in which it cannot be applied by any other means. After directing his attention for several years to this object, and performing a great variety of experiments in the prosecution of it, he at last succeeded in the construction of a lens, of flint-glass, three feet in diameter, which, when fixed in its frame, exposes a surface two feet eight inches and a half in the clear, without any other material imperfection, except a disfigurement of one of the edges by a piece of the scoria of the mould, which unfortunately found its way into its substance. This lens was double-convex, both sides of which were a portion of a sphere of eighteen feet radius. It is difficult to form an accurate estimate of the burning power of this lens; inasmuch as it is next to impossible to discover what should be deducted for the loss of power, in consequence of the impediments that the glass of which it was made must occasion, as well as the four reflections, and two more by way of diminution; but we will endeavour to appreciate it, after a full allowance for these deductions, which must necessarily result from every means of concentrating the solar rays, and must be considered as the friction of an engine, of which nature they really partake.

The solar rays received on a circular surface of two feet eight inches and a half, when concentrated within the diameter of an inch, will be 105,626 times its intensity, or this number of times greater than the heat of the sun as it is experienced on the surface of the earth. We will suppose, that as the heat of the air, in ordinary summer weather, is 65 degrees, and in sultry weather is 75 degrees, the average of which is 70 degrees, and that we take this as the average effect, the accumulated power of the lens, on the supposition of an uniform heat over the whole surface of the focus, will be equal to 73,938 degrees. It must be recollected, by those who have an opportunity of examining the effects of this lens, that the external part of the focal light was less intense than that part which was near the centre of it; or rather, that the effect was very much accumulated in the centre; but as it is possible that the refraction of the light and of the caloric fluid may not take place in the same angles, we think it safest to consider it as of uniform effect, and alter deducting one fourth part thereof as a compensation, there remains 5545 as the expression of its power. As the application of the second lens reduced the diameter of the focus to half an inch, the effect, without allowing for the reduction of its power, would be equal to 221,816 degrees; but deducting one-fourth for the second transmission, there remains 166,362 degrees, as the expression of its power.

Mr. Parker further informs us, that a diamond, weighing ten grains, exposed to this lens for thirty minutes, was reduced to six grains; during which operation it opened and foliated like the leaves of a flower, which emitted whitish fumes, and when closed again, bore a polish, and retained its form. Gold remained in its metallic state without apparent diminution, notwithstanding an exposure at intervals of many hours: but what is remarkable, the rest, or cupel, which was composed of bone-ash, was tinctured with a beautiful pink colour.

The experiments on platina evince that the specimens were in different states of approach to a complete metallic form; several of them threw off their parts in sparks, which in most instances were metallic. Copper, after three minutes' exposure, was not found to have lost in weight.

What is remarkable with regard to experiments on iron, is, that the lower part, i. e. that part in contact with the charcoal, was first melted, when that part which was exposed to the focus remained unfused; an evidence of the effect of flux on this metal.

Several of the semi-crystalline substances, exposed to the focal heat, exhibited symptoms of fusion; such as the agate, oriental flint, cornelian, and jasper: but as the probability is, that these substances were not capable of complete vitrification, it is enough that they were rendered externally of a glassy form. Garnet completely fused on black lead in 120 seconds, lost a quarter of a grain, became darker in colour, and was attracted by the magnet. Ten cut garnets taken from a bracelet began to run the one into the other in a few seconds, and at last formed into one globular garnet. The clay used by Mr. Wedgwood to make his pyrometric test, run in a few seconds into a white enamel. Seven other kinds of clay, sent by Mr. Wedgwood, were all vitrified. Several experiments were made on limestone, some of which were vitrified, but all of which were agglutinated; it is, however, suspected that some extraneous substance must have been intermixed. A globule produced from one of the specimens, on being put into the mouth, flew into a thousand pieces, occasioned, it is presumed, by the moisture.

A subscription was proposed for raising the sum of seven hundred guineas, towards indemnifying the charges of the inventor, and retaining the very curious and useful machine above described in our own country; but from the failure or the subscription, and some other concurring circumstances, Mr. Parker was induced to dispose of it to Capt. Mackintosh, who accompanied Lord Macartney in the embassy to China: and it was left, much to the regret of philosophers in Europe, at Pekin; where it remains in the hands of persons, who most probably know neither its value nor use.

DUCTILITY OF GLASS.--We all know, that when glass is well penetrated with the heat of the fire, the workmen can figure and manage it like soft wax; but, what is most remarkable, it may be drawn, or spun out, into threads exceedingly long and fine. Our ordinary spinners do not form their threads of silk, flax, or the like, with half the ease and expedition the glass-spinners do threads of this brittle matter. We have some of them used in plumes for children's heads, and divers other works, much finer than any hair, and which bend and wave, like hair, with every wind. Nothing is more simple and easy than the method of making them. There are two workmen employed: the first holds one end of a piece of glass over the flame of a lamp; and when the heat has softened it, a second operator applies a glass hook to the metal thus in fusion, and, withdrawing the hook again, it brings with it a thread of glass, which still adheres to the mass; then, fitting his hook on the circumference of a wheel about two feet and a half in diameter, he turns the wheel as fast as he pleases, which, drawing out the thread, winds it on its run, till, after a certain number of revolutions, it is covered with a skein of glass-thread. The mass in fusion over the lamp diminishes insensibly, being wound out like a clue of silk upon the wheel; and the parts cooling as they recede from the flame, become more coherent to those next to them, and this by many degrees: the parts nearest the fire are always the least coherent, and, of consequence, must give way to the effort the rest make to draw them towards the wheel. The circumference of these threads is usually a flat oval, being three or four times as broad as thick: some of them seem scarcely bigger than the thread of a silkworm, and are surprisingly flexible. If the two ends of such threads are knotted together, they may be drawn and bent, till the aperture, or space in the middle of the knot, does not exceed one-fourth of a line, or one forty-eighth of an inch in diameter. Hence M. Reaumur maintains, that the flexibility of glass increases in proportion to the fineness of the threads; and that, probably, had we but the art of drawing threads as fine as a spider's web, we might weave stuffs and cloths of them for wear. Accordingly, he made some experiments this way; and found that he could make threads fine enough, viz. as fine, in his judgment, as spider's thread, but not long enough for the purposes of any manufacture.