Chapter V: Introduction: Of the Potato (2)

The late Earl of Rosse, with a devotion to science which has few parallels, constructed this gigantic telescope, at his seat, Parsonstown, in the south of Ireland. To the frame of the vast instrument is fixed a large cubical wooden box, about eight feet wide; in this there is a door, through which two men go in to remove, or to replace, the cover of the mirror. To this box is fastened the tube, which is made of deal staves, and hooped like a huge cask. It is about 40 feet long, and 8 feet diameter in the middle. _The Dean of Ely once walked through the tube with an umbrella up!_ The stupendous speculum weighs three tons; the casting and polishing of it were labours of wonderful skill. The telescope is not turned to any part of the sky, but limited to the range of half an hour on each side of the meridian, through which its motion is given by powerful clockwork, independent of the observer. For this purpose it stands between two pieces of masonry, of gothic design, which harmonize with Lord Rosse's castle; one of these piers sustaining the galleries for the observer, and the second the clockwork and other apparatus. There is an elegant arrangement of counterpoises to balance the enormous mass, so that a comparatively slight force only is required to elevate or depress it. A correspondent of the _Mechanics' Magazine_ thus describes the capacity of this wonderful instrument:--

"Such is its power, that if a star of the first magnitude were removed to such a distance, that its light would be three millions of years in reaching us, this telescope would, nevertheless, show it to the human eye. Is it to be wondered at, then, that, with such an instrument, grand discoveries should be made? It has been pointed to the heavens; and, although in the beginning of its career, it has already accomplished mighty things. There are nebulous spots in the heavens which have baffled all the instruments hitherto constructed, but this telescope resolves their true character completely. Among the wonderful objects which have been subject to its scrutiny, is the nebula in the constellation of Orion. I have had an opportunity of examining it. It is one of the most curious objects in the whole heavens. It is not round, and it throws off furious lights. From the time of Herschel it has been subjected to the examination of the most powerful instruments--but it grew more and more mysterious and diverse in its character. When Lord Rosse's great telescope was directed to its examination, it for a long time resisted its power. He found it required patient examination--night after night, and month after month. At length, a pure atmosphere gave him the resolution of its constitution; and the stars of which it is composed burst upon the sight of man for the first time!"

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ORIGIN OF REFLECTING LIGHTHOUSES.

In the last century, at a meeting of a society of mathematicians at Liverpool, one of the members proposed to lay a wager, that he would read a paragraph of a newspaper, at ten yards' distance, with the light of a farthing candle. The wager was laid, and the proposer, having covered the inside of a wooden dish with pieces of looking-glass, fastened in with glaziers' putty, placed his reflector behind the candle, and won his wager. One of the company marked this experiment with a philosophic eye. This was Captain Hutchinson, the dockmaster, with whom originated the reflecting lighthouses, erected at Liverpool in 1763.

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WASTE OF HUMAN LIFE.

In 1825, there was opened in Cochin-China a canal, 23 miles long, 80 feet wide, and 12 feet deep. It was begun and finished in six weeks, although carried through large forests and over extensive marshes. Twenty thousand men worked upon it day and night; and it is stated that 7,000 died of fatigue.

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LIFTING HEAVY PERSONS.

One of the most extraordinary pages in Sir David Brewster's _Letters on Natural Magic_, is the experiment in which a heavy man is raised with the greatest facility, when he is lifted up the instant that his own lungs, and those of the persons who raise him, are inflated with air. Thus, the heaviest person in the party lies down upon two chairs, his legs being supported by the one, and his back by the other. Four persons, one at each leg, and one at each shoulder, then try to raise him--the person to be raised giving two signals, by clapping his hands. At the first signal, he himself and the four lifters begin to draw a long and full breath, and when the inhalation is completed, or the lungs filled, the second signal is given for raising the person from the chair. To his own surprise, and that of his bearers, he rises with the greatest facility, as if he were no heavier than a feather! Sir David Brewster states that he has seen this inexplicable experiment performed more than once; and he appeals for testimony to Sir Walter Scott, who had repeatedly seen the experiment, and performed the part, both of the load and of the bearer. It was first shown in England by a gentleman who saw it performed in a large party at Venice, under the direction of an officer of the American navy.

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ORIGIN OF THE SOCIETY OF ARTS.

"To this Society," a well-informed writer has said, "some of our best artists have owed the most priceless of all services that can be rendered to men of genius at the outset of their career--appreciation on the part of an enlightened few--introduction under favourable auspices to the many."

The Society of Arts was established in 1754, chiefly by Mr. William Shipley, a drawing-master; but it was not until 1774 that the institution was fairly located in its own premises, built in handsome style by the Adams', in John Street, Adelphi; the object being denoted by the inscription upon the entablature of the pediment in the front of the mansion, in these words: "Arts and Commerce promoted."

There are many interesting anecdotes of the early awards of this Society. Thus, in 1758, Bacon, the sculptor, received for a small figure of Peace a reward of ten guineas; and the same artist gained the highest premium upon nine different occasions. In 1761, Nollekens received ten guineas for an alto-relievo of Jephtha's Vow; and two years later, fifty guineas for a more important piece of sculpture. Flaxman, in 1768, gained for one of his earliest attempts a grant of ten guineas; and for another work, in 1771, he obtained the Society's gold medal. Lawrence, at the early age of thirteen, received the reward of a silver-gilt palette, with five guineas, for his drawing in crayons of the Transfiguration; and the painter in the height of his subsequent prosperity, was accustomed to speak of the impulse thus given to his love of art. In 1807, Sir William Ross, at the age of twelve, received the Society's silver palette for a drawing of the death of Wat Tyler; Mr. Edwin Landseer gained a similar mark of approbation in 1810, for an etching; and to Mr. Wyon was adjudged the gold medal, in 1818, for a medal die. But to artists there is a feature of still greater interest in the Society's history: it was in its rooms that the first exhibition of paintings in England took place in 1760, which was continued with great success for some years.

Within about ninety years, the Society had distributed more than 100,000_l._ in premiums. The growth of forest trees was one of its early objects of encouragement; and we find among the recipients of its gold medals the Dukes of Bedford and Beaufort, the Earls of Winterton, Upper Ossory, and Mansfield; and Dr. Watson, Bishop of Llandaff. Then came agriculture, chemistry, manufactures, and mechanics. In the latter, the Society taught us, or at least aided those who did so, the manufacture of Turkey carpet, tapestry, weaving, and weaving to imitate the Marseilles and India quilting; also, how to improve our spinning and lace-making, our paper, and our catgut for musical instruments, our straw-bonnets, and artificial flowers.

The colonies shared in the Society's early encouragement: potash and pearlash were produced by its agent in North America; and it was busily engaged, just before the breaking out of the war of independence, in introducing the culture of the vine, the growth of silk-worms, and the manufacture of indigo and vegetable oils. But the rewards given to poor Bethnal-green and Spitalfields weavers, for useful inventions in their calling, illustrate, perhaps even better than any of the foregoing instances, the object of the Society which so honourably distinguishes it from other associations--its readiness to receive, examine, and reward every kind of useful invention that may be brought forward by those who have neither friends nor money to aid them in making their inventions known.

Nor must we forget Barry's grand series of paintings upon the Society's large room; of which Dr. Johnson said, "there is a grasp of mind there, which you will find nowhere else." Upon the walls, too, hang some fine portraits of the early presidents of the Society, painted by Sir Joshua Reynolds.

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VAST MIRRORS.

Mirrors are cast of larger dimensions at St. Petersburg than elsewhere. In the imperial manufactory, there was cast for Prince Potemkin, a mirror measuring 194 inches by 100. One of the same proportions, valued at 3000 guineas, was cast for the Duke of Wellington many years since, but was broken to atoms in its conveyance from St. Petersburg to England.

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TRANSPORTATION OF THE COFFEE-TREE.

One of the most interesting episodes in the history of coffee is, that of the transportation of the plant of the coffee-tree, taken from the hothouses of Amsterdam, given to Louis XIV., and father of the three plants, one of which was taken to the French Antilles by Captain Declieux, who, in a scarcity of water experienced by the ship's crew, shared the small quantity which he had to drink, between himself and his dear coffee-plant. It is believed that from this plant has sprung all the coffee grown in the West Indies.

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ARKWRIGHT'S SPINNING FRAME.

Mr. Arkwright tells us, that he accidentally derived the first hint of this great invention from seeing a red-hot iron bar elongated by being made to pass between rollers; and, though there is no mechanical analogy between that operation and the process of spinning, it is not difficult to imagine that, by reflecting upon it, and placing the subject in different points of view, it might lead him to his invention.

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SPINNING FEATS.

Among the wonders of this branch of manufacture, the following deserve mention:--In 1745, a woman at East Dereham, in Norfolk, spun a single pound of wool into a thread of 84,000 yards in length, wanting only 80 yards of forty-eight miles, which, at the above period, was considered a circumstance of sufficient curiosity to merit a place in the records of the Royal Society. Since that time, however, a young lady of Norwich has spun a pound of combed wool into a thread of 168,000 yards; and she actually produced from the same weight of cotton a thread of 203,000 yards, equal to upwards of 115 miles:--this last thread, if woven, would produce about twenty yards of yard-wide muslin.

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MARVELS OF THE ALCHEMISTS.

The pretended secret of the Alchemists was the transmutation of the baser metals into gold, which they occasionally exhibited to keep the dupes who supplied them with money in good spirits. This they performed in various ways. Sometimes they made use of crucibles with a false bottom. At the real bottom, they put a quantity of gold or silver. This was covered by a portion of powdered crucible mixed with gum or wax, and hardened. The material being put into a crucible and the heat applied, the false bottom disappeared; and at the end of the process, the gold or silver was found at the bottom of the crucible. Sometimes, they made a hole in a piece of charcoal, filled it with oxide of gold or silver, and stopped up the hole with a little wax; or they soaked the charcoal in solutions of these metals; or they stirred the mixture in the crucible with hollow rods, containing oxide of gold or silver within, and the end closed with wax. By these means, the gold or silver wanted was introduced during the operation, and considered as a product.

Sometimes the cunning wights used solutions of silver in nitric acid, or of gold in aqua-regia, or an amalgam of gold or silver, which being adroitly introduced, furnished the requisite quantity of metal. A common exhibition was to dip nails into a liquid, and take them out, half converted into gold. The nails were one-half gold and the other half iron, neatly soldered together, and the gold was covered with something to conceal the colour, which the liquid was capable of removing.

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INVENTION OF THE HAND GEAR.

It has been said that we are indebted for the important invention in the steam-engine, termed hand gear, by which its valves or cocks are worked by the machine itself, to an idle boy named Humphrey Potter, who, being employed to stop and open a valve, saw that he could save himself the trouble of attending and watching it, by fixing a plug upon a part of the machine which came to the place at the proper times, in consequence of the general movement. If this anecdote be true, what does it prove? That Humphrey Potter might be very idle, but that he was, at the same time, very ingenious. It was a contrivance, not the result of accident, but of acute observation and successful experiment.--_Dr. Paris._

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POKER ACROSS THE FIRE.

Boswell and Johnson held a conversation upon this experiment as follows:--_Boswell._ "Why, sir, do people play this trick, which I observe now when I look at your grate, putting the shovel against it to make the fire burn?"--_Johnson._ "They play the trick, but it does not make the fire burn. _There_ is a better (setting the poker perpendicularly up at right angles with the grate.) In days of superstition, they thought, as it made a cross with the bars, it would drive away the witch."

Upon this, Dr. Kearney notes: "it certainly does make the fire burn: by repelling the air, it throws a blast upon the fire, and so performs the parts, in some degree, of a blower or bellows." These observations were made only as to the shovel, but the poker is equally efficacious. "After all," says Croker, "it is possible that there may be some magnetic or electrical influence, which, in the progress of science, may be explained; and what has been thought a vulgar trick, may be proved to be a philosophical experiment."

Whatever may be the cause, there is every-day evidence that a poker or shovel, as the case may be, if laid across a dull fire, will revive it; because, we think, the poker or shovel receives and concentrates the heat, and produces an additional draught through the fire.

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THE ARTESIAN WELL OF GRENELLE, AT PARIS.

The boring of this well by the Messrs. Mulot occupied seven years, one month, twenty-six days, to the depth of 1794-1/2 English feet, or 194-1/2 feet below the depth at which M. Elie de Beaumont foretold that water would be found. The sound, or borer, weighed 20,000 lb., and was treble the height of that of the dome of the Hospital des Invalides, at Paris. In May, 1837, when the bore had reached 1246 feet 8 inches, the great chisel and 262 feet of rods fell to the bottom; and, although these weighed five tons, M. Mulot tapped a screw on the head of the rods, and thus, connecting another length to them, after fifteen months' labour, drew up the chisel! On another occasion, this chisel having been raised with great force, sunk at one stroke 85 feet 3 inches into the chalk![7]

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Footnote 7:

The depth of the Grenelle Well is nearly four times the height of
Strasburg Cathedral; more than six times the height of the Hospital
des Invalides, at Paris; more than four times the height of St.
Peter's, at Rome; nearly four times and a half the height of St.
Paul's, and nine times the height of the Monument, London. Lastly,
suppose all the above edifices to be piled upon each other, from the
base-line of the Well of Grenelle, and they would but reach within
11-1/2 feet of its surface.--_Year-Book of Facts_, 1843.

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"WET THE ROPES."

The property of cords contracting their length by moisture became generally known, it is said, on the raising of the Egyptian obelisk in the square facing St. Peter's, at Rome, by order of Pope Sixtus V. The great work was undertaken in the year 1586, and the day for raising the obelisk was marked with great solemnity. High mass was celebrated at St. Peter's, and the architect and workmen received the benediction of the Pope. The blast of a trumpet was the given signal, when engines were set in motion by an incredible number of horses; but not until after fifty-two unsuccessful attempts had been made, was the huge block lifted from the earth. As the ropes which held it had somewhat stretched, the base of the obelisk could not reach the summit of the pedestal, when a man in the crowd cried out, "_Wet the ropes!_" This advice was followed, and the column, as of itself, gradually rose to the required height, and was placed upright on the pedestal prepared for it.

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THE DEATH OF DR. BLACK.

In the society of friends such as Adam Smith, Hume, Carlyle, Home, Hutton, Playfair, and Dugald Stewart, the closing days of this great and gentle chemist wore tranquilly away. Towards the end, he sank into a low state of health, and only preserved himself from the severe shocks of the weather in the changeable climate of Edinburgh, by a degree of care and abstemiousness rarely surpassed even by the devoutest Brahmin. "It was his generous and manly wish, that he might never live to be a burden to his friends; and never was the wish more completely gratified. On the 26th November 1799, in the seventy-first year of his age, he expired without any convulsion, shock, or stupor, to announce or retard the approach of death. Being at table with his usual fare--some bread, a few prunes, and a measured quantity of milk diluted with water; and having the cup in his hand when the last stroke of the pulse was to be given, he had set it down upon his knees, which were joined together, and kept it steady with his hand in the manner of a person perfectly at ease; and in this attitude expired, without spilling a drop, and without a writhe in his countenance; as if an experiment had been required, to show to his friends the facility with which he departed. His servant opened the door to tell him that some one had left his name; but getting no answer, stepped about half way towards him, and, seeing him sitting in that easy posture, supporting his basin of milk with one hand, he thought that he had dropped asleep, which he had sometimes seen happen after his meals. The man went back and shut the door; but before he got down stairs, some anxiety that he could not account for made him return, and look again at his master. Even then, he was satisfied, after coming pretty near, and turned to go away; but again returned, and coming quite close, found his master without life."

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ORIGIN OF THE TELEGRAPH.

When Arthur Young made his well-known journey in France, in the year 1787 to 1789, he met, he tells us, with a Monsieur Lomond, "a very ingenious and inventing mechanic," who had made a remarkable discovery in electricity. "You write two or three words on a paper," says Young: "he takes it with him into a room, and turns a machine enclosed in a cylindrical case, at the top of which is an electrometer, a small, fine, pith ball; a wire connects with a similar cylinder and electrometer in a distant apartment; and his wife, by remarking the corresponding motions of the ball, writes down the words they indicate; from which it appears that he has formed an alphabet of motions. As the length of the wire makes no difference in the effect, a correspondence might be carried on at any distance. Whatever the use may be, the invention is beautiful." This discovery, however, lay unnoticed until about the year 1845; though the apparatus was designed to effect the same end as the electric telegraph, by means very similar.

The possibility of applying electricity to telegraphic communication was conceived by several other persons, long before it was attempted upon a practical scale. The Rev. Mr. Gamble, in his description of his original shutter-telegraph, published towards the close of the last century, alludes to a project of electrical communication. Mr. Francis Ronalds, in a pamphlet on this subject, published in 1823, states that Cavallo proposed to convey intelligence by passing given numbers of sparks through an insulated wire; and that, in 1816, he himself made experiments upon this principle, which he deemed more promising than the application of galvanic or voltaic electricity, which had been projected by some Germans and Americans. He succeeded perfectly in transmitting signals through a length of eight miles of insulated wire; and he describes minutely the contrivances necessary for adapting the principle to telegraphic communication.

It is, however, to the combined labours of Mr. W. F. Cooke and Professor Wheatstone that electric telegraphs owe their practical application; and, in a statement of the facts respecting their relative positions in connection with the invention, drawn up at their request by Sir M. I. Brunel and Professor Daniell, it is observed that "Mr. Cooke is entitled to stand alone, as the gentleman to whom this country is indebted for having practically introduced and carried out the electric telegraph as a useful undertaking, promising to be a work of national importance; and Professor Wheatstone is acknowledged as the scientific man whose profound and successful researches had already prepared the public to receive it as a project capable of practical application."--_Penny Cyclopædia._

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NECESSITY THE MOTHER OF INVENTION.

When Vitiges, king of the Goths, besieged Belisarius in Rome in 536, and caused the fourteen large aqueducts to be stopped, the city was subjected to great distress, not on account of the want of water in general, for it was secured against that inconvenience by the Tiber, but on account of the loss of that water which the baths required, and, above all, of that necessary to drive the mills, which were all situated on these canals. Horses and cattle, which might have been employed in grinding, were not to be found; but Belisarius, a man of great ingenuity, devised an expedient to remedy this distress. Below the bridge that reached to the wall of Janiculum, he extended ropes, well fastened, and stretched across the river from both banks. To these he affixed two boats of equal size, at the distance of two feet from each other, where the current flowed with the greatest rapidity, under the arch of the bridge; and, placing large millstones on one of the boats, suspended in the middle space a machine by which they were turned. He constructed at certain intervals on the river other machines of the same description, which, being put in motion by the force of the water that ran below them, drove as many mills as were necessary to grind provisions for the city. To destroy these, the besiegers threw into the stream logs of wood, and dead bodies, which floated down the river into the city; but the besieged, by making use of booms to stop them, were enabled to drag them out before they did any mischief. This is said to have been the first invention of floating mills.

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A "DRY-MAKING" IN HOLLAND.

The conversion into solid land of the Lake of Beemster, in North Holland, is, after the Haarlemmermeer Polder (which is twice and a half its size), the largest specimen in the Netherlands of what the Dutch term "dry-makings." The scheme was first broached in 1570. In 1592 funds were applied for, which were not, however, promised by the States of Holland and West Friesland until 1597. In 1607, a company was formed at the Hague, by Dirck van Oss and others, to pump out the Beemster in whole or in part; and on their security the States lent the necessary capital. At the commencement, it was thought that sixteen windmills would suffice for the undertaking; but this number was shortly increased by ten, and the twenty-six mills were then divided into thirteen gangs. By the end of 1608, several of the mills began to pump, and early in 1609, they were all ready. Towards the end of this year, the bottom of the lake became visible in some places: but during a storm on the 23d of January 1610, the great waterland sea dyke gave way, and the pressure on the ring dyke that had been constructed round the Beemster proved greater than it was capable of resisting. It gave way in turn in two places, and the lake was again filled. On the 5th February 1610, further and ample funds were advanced by the States; in 1611, more mills were put on to the work; on the 19th of May 1612, the dry-making was at last completed; and on the 30th July of that year, the distribution of the lots of land redeemed took place. The ring dyke is over 37,000 yards long, and has an average height of × 1·50 Z. P. (a metre and a half above the mean level of the sea). Thus was the Beemster pumped out; and from that day to the present, the name of Dirck van Oss has been held in deep respect in Holland, as the name of the first Dutchman who conquered the waters on anything like a large scale. The system he employed has been closely followed in all successive undertakings of this kind; and, with the exception of the application of steam, and certain improvements in machinery, the plans of Dirck van Oss for draining the Beemster were adapted with a like success to the Lake of Haarlem, by M. Gevers d'Endegeest, the hero of this last conquest, and the sanguine prophet (1867) of the ultimate reclamation of the Zuyder Zee. The drainage of the Lake of Haarlem, it may be mentioned, was accomplished in 1852, after thirteen years of toil and anxiety, at a cost of 11,000,000 florins (£916,666); a sum which, large as it is, has nevertheless been completely recovered, both in capital and interest, by the sale of 42,481 acres of arable land.--_Report to Foreign Office._

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A SCIENTIFIC PILGRIM.

When Lord Napier (of Merchiston) first published his _Logarithms_, Mr. Briggs, Professor of Mathematics at Gresham College, London, was so surprised with admiration, that he could not rest till he had seen the noble inventor, and actually went to Scotland for that purpose in 1615. Lilly, the astrologer, thus describes the interview:--"Mr. Briggs appointed a certain day when to meet at Edinburgh; but, failing thereof, Merchiston was afraid he would not come. It happened one day, as John Marr and the Lord Napier were speaking of Mr. Briggs: 'Ah! John,' said Merchiston, 'Mr. Briggs will not come.' At the very instant, one knocks at the gate; John Marr hastens down, and it proved to be Mr. Briggs, to his great contentment; he brings Mr. Briggs up into my Lord's chamber, where almost one quarter of an hour was spent, each beholding the other with admiration before one word was spoken. At last, Mr. Briggs began, 'My Lord, I have undertaken this long journey purposely to see your person, and to know by what engine of wit or ingenuity you came first to think of this most excellent help unto astronomy, viz. the logarithms; but, my Lord, being by you found out, I wonder nobody else found it out before, when now, being known, it appears so easy.'" Briggs was nobly entertained by Lord Napier; and every summer after, during his lordship's life, this venerable man went to Scotland purposely to see him.

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THE BURNING MIRRORS OF ARCHIMEDES.

Many have questioned the facts recorded by several historians, concerning the surprising effects of the burning mirrors of Archimedes, by means of which the Roman galleys besieging Syracuse were consumed to ashes. Descartes, in particular, discredited the story as fabulous; but Kircher made many experiments with a view of testing its credibility. He tried the effect of a number of plane mirrors; and, with five mirrors of the same size, placed in a frame, he contrived to throw the rays reflected from them to the same spot, at the distance of more than 100 feet; and by this means he produced such a degree of heat, as led him to conclude that, by increasing their number, he could have set fire to inflammable substances at a greater distance. He likewise made a voyage to Syracuse, in company with his pupil Schottius, in order to examine the place of the alleged transaction; and they were both of opinion, that the galleys of Marcellus could not have been more than thirty paces from Archimedes' mirrors.

M. Buffon also constructed a machine, consisting of a number of mirrors, by which he seems to have revived the secret of Archimedes, and to have vindicated the credit of history in this respect. His experiment was first made with twenty-four mirrors, which readily set fire to combustible matter composed of pitch and tow, and laid on a deal board at the distance of seventy-two feet. He further pursued the attempt by framing a kind of polyhedron, consisting of 168 pieces of plane looking-glass, each six inches square; and by means of this machine, some boards of beech-wood were set on fire at the distance of 150 feet, and a silver plate was melted at the distance of 60 feet. This machine, in the next stage of its improvement, contained 360 plane mirrors, each eight inches long and six broad, mounted on a frame eight feet high and seven broad. With twelve of these mirrors, light combustible matter was kindled at the distance of twenty feet; with forty-five of them, at the same distance, a large tin vessel was melted, and with 117, a thin piece of silver. When the whole machine was employed, all the metals and metallic minerals were melted at the distance of twenty-five and even of forty feet. Wood was kindled in a clear sky at the distance of 210 feet. M. Buffon afterwards constructed a machine which contained 400 mirrors, each six inches square, with which he could melt lead and tin at the distance of 140 feet.

But perhaps the most powerful burning mirror ever constructed, was that of Mr. Parker, an eminent glass manufacturer of London; it was made in the begining of this century by one Penn, an ingenious artisan of Islington. He erected an outhouse at the bottom of his garden, for the purpose of carrying on his operations, and at length succeeded in producing, at a cost of £700, a burning lens of a diameter of three feet, whose powers were astonishing. The most hard and solid substances of the mineral world, such as platina, iron, steel, flint, &c., were melted in a few seconds, on being exposed to its immense focus. 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, and emitted whitish fumes; when closed again, it bore a polish, and retained its form. Ten cut garnets, taken from a bracelet, began to run into each other in a few seconds, and at last formed one globular garnet. The clay used by Wedgewood to make his pyrometric test ran in a few seconds into a white enamel; and several specimens of lavas, and other volcanic productions, on being exposed to the focus of the lens, yielded to its power.

A subscription was proposed in London to raise the sum of 700 guineas, in order to indemnify the inventor for the expense he had incurred in its construction, and retain it in England; but, through the failure of the subscription, and other concurring circumstances, Mr. Parker was induced to dispose of it to Captain Mackintosh, who accompanied Lord Macartney in his celebrated embassy to China; and the mirror, much to the loss and regret of European science, was left at Pekin.

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MAGNETIC CORRESPONDENCE IN THE
SEVENTEENTH CENTURY.

In one of Addison's contributions to the _Spectator_ (No. 241), we find the following curious instance of what may almost be considered as the foreshadowing of the electric telegraph. It is quoted from the writings of Strada, the celebrated Roman Jesuit, who died in 1649. In his "Prolusiones," a series of polished Latin essays upon rhetoric and literature, he gives an account of a chimerical correspondence between two friends, by the help of a certain loadstone, which had such virtue in it, that if touched by two several needles, when one of the needles so touched began to move, the other, though at ever so great a distance, moved at the same time and in the same manner. He tells us that two friends, being each of them possessed of these needles, made a kind of dial-plate, inscribing it with twenty-four letters--in the same manner as the hours of the day are marked upon the ordinary dial-plate. They then fixed one of the needles on each of these plates, in such a manner that it could move round without impediment so as to touch any of the twenty-four letters. Upon their separating from one another into distant countries, they agreed to withdraw themselves punctually into their closets at a certain hour of the day, and to converse with one another by means of this their invention. Accordingly, when they were some hundred miles asunder, each of them shut himself up in his closet at the time appointed, and immediately cast his eye upon his dial-plate. If he had a mind to write anything to his friend, he directed his needle to every letter that formed the words that he had occasion for--making a little pause at the end of every word or sentence, to avoid confusion. The friend, in the meanwhile, saw his own sympathetic needle moving of itself to every letter which that of his correspondent pointed at. By this means, they talked together across a whole continent, and conveyed their thoughts to one another, in an instant, over cities or mountains, seas or deserts.... In the meanwhile (adds the Essayist, playfully), if ever this invention should be revived, or put in practice, I would propose that upon the lovers' dial-plate there should be written, not only the twenty-four letters, but several entire words which have always a place in passionate epistles; as flames, darts, die, languish, absence, Cupid, heart, eyes, hang, drown--and the like. This would very much abridge the lover's pains in this way of writing a letter--as it would enable him to express the most useful and significant words with a single turn of the needle.

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NAVIGATION BEFORE THE COMPASS.

Before the invention of the mariner's compass, the Phoenician, the Greek, and the early Italian navigators were compelled to creep from headland to headland, without venturing to quit the shore--except when an island, so near as to be distinctly seen from the continent, offered them an equally secure retreat from the violence of an accidental tempest. Yet, the bolder Norwegians, though exposed to far greater perils, from the habitual inclemency of a high northern latitude, and from the frequent cloudiness of their atmosphere, were in the habit of attempting, and often with success, a voyage of some length upon the ocean. It may be supposed that a patient observation of natural phenomena, attention to the flight of migratory birds and to the direction of currents, and some few simple devices which, being no longer necessary, are now forgotten, served as substitutes for the more valuable guides of modern navigation. Of one of the devices here enumerated, it is related that when Flok, a famous Norwegian navigator, was about to set out from Shetland for Iceland, then called Gardarsholm, he took on board some crows, "because the mariner's compass was not yet in use." When he thought he had made a considerable part of his way, he threw up one of his crows, which, seeing land astern, flew to it; whence Flok, concluding that he was nearer to Shetland (or perhaps Faroë) than any other land, kept on his course for some time, and then sent out another crow, which, seeing no land at all, returned to the vessel. At last, having run the greater part of his way, another crow was sent out by him, which, seeing land ahead, immediately flew for it; and Flok, following his guide, fell in with the east end of the island. Such was the simple mode of steering their course, practised by those bold navigators of the stormy northern ocean. This story at once and strikingly recalls the use made of birds by the first sea captain of whom we read--Noah; but such expedients evidently could not be supposed to have inspired the old northern navigators with the courage and confidence that enabled them, as there is reason to believe, to discover America before Columbus.

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SEMAPHORE _v._ ELECTRIC TELEGRAPH.

An anecdote will suffice to illustrate the advantages of the electric over the visual variety of telegraph--the one being only workable in certain states of the weather; the other available in all states. Upon one occasion, when the British army were fighting in Spain, intelligence was every day feverishly expected from Wellington through the medium of the semaphore at the Admiralty. Long delayed, it came at last, and was apparently of a fearful character. It ran thus: "Wellington defeated." Parliament and the people were stunned for a time, and rumours flew about like wildfire to this effect. It turned out, however, that just as the word "defeated" was deciphered, a fog intervened, and cut off the rest of the communication. When the dark pall disappeared, the bright sky disclosed to a jubilant people, not "Wellington defeated," but "Wellington defeated--the French!"

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A WRENCH TO OLD ST. PAUL'S.

When, after much mean and yet costly endeavour to patch up the cathedral of St. Paul's, after the great fire, Sir Christopher Wren at last had his advice accepted, to rebuild the whole structure, the demolition of the old fabric gave ample play to his scientific knowledge and engineering skill. One of his exploits, perhaps now more remarkable because at the time it was at once rare and bold, has thus been described:--"In order that the rubbish and old materials might not hinder the setting out of the foundations, for the purpose of proceeding with the works, Sir Christopher constructed scaffolds high enough to extend his lines over the heaps that were in the way; and thereby caused perpendiculars to be fixed upon the points below for his various walls and piers, from lines drawn carefully upon the level plan of the scaffold. Thus he proceeded, gaining every day more and more room, till he came to the middle tower that formerly carried the lofty spire. The ruins of this tower being nearly two hundred feet high, the labourers were afraid to work above, which induced him to facilitate the labour by the use of gunpowder. To perform this work, he caused a hole to be dug, of about four feet wide, by the side of the north-west pier of the tower, in which was perforated a hole two feet square, reaching to the centre of the pier. In this he placed a small deal box containing eighteen pounds of gunpowder. To this box he affixed a hollow cane, which contained a quick match, reaching to the surface of the ground above; and along the ground a train of powder was laid, with a match. The mine was then closed up, and exploded, while the philosophical architect waited with confidence the result of his experiment. This small quantity of powder not only lifted up the whole angle of the tower, with two great arches that rested upon it, but also two adjoining arches of the aisle, and the masonry above them. This it appeared to do in a slow but efficient manner, cracking the walls to the top, lifting visibly the whole weight about nine inches, which suddenly dropping, made a great heap of ruins in the place, without scattering or accident. It was half a minute before the heap already fallen opened in two or three places, and emitted smoke. By this successful experiment, the force of gunpowder may be ascertained; eighteen pounds only of which lifted up a weight of more than three thousand tons, and saved the work of a thousand labourers. The fall of so great a weight from a height of two hundred feet gave such a concussion to the ground, that the inhabitants round about took it for the shock of an earthquake."

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SNOW SPECTACLES.

Ellis, in his _Voyage to Hudson's Bay_, written in the middle of last century, says of the Esquimaux:--"Their snow eyes, as they very properly call them, are a proof of their sagacity. They are little pieces of wood or ivory, properly formed to cover the organs of vision, and tied on behind the head. They have two slits, of the exact length of the eyes, but very narrow; and they see through them very distinctly, and without the least inconvenience. This invention preserves them from snow-blindness, a very dangerous and powerful malady, caused by the action of the light strongly reflected from the snow, especially in the spring, when the sun is considerably elevated above the horizon. The use of these eyes considerably strengthens the sight, and the Esquimaux are so accustomed to them, that when they have a mind to view distant objects, they commonly use them instead of spy-glasses."

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A SELF-TAUGHT MECHANIST.

The following description is given of an ingenious and singular piece of mechanism--constructed by a boy of the name of John Young, who in 1819 resided at Newton-on-Ayr--which attracted much notice among the scientific of the day:--"A box, about three feet long by two broad, and six or eight inches deep, had a frame and paper covering erected on it, in the form of a house. On the upper part of the box are a number of wooden figures, about two or three inches high, representing people employed in those trades and sciences with which the boy is familiar. The whole are put in motion at the same time by machinery within the box, acted upon by a handle like that of a hand-organ. A weaver upon his loom, with a fly-shuttle, uses his hands and feet, and keeps his eye upon the shuttle, as it passes across the web. A soldier, sitting with a sailor at a public-house table, fills a glass, drinks it off, then knocks upon the table, upon which an old woman opens a door, makes her appearance, and they retire. Two shoemakers upon their stools are seen, the one beating leather, and the other stitching a shoe. A cloth-dresser, a stone-cutter, a cooper, a tailor, a woman churning, and one teasing wool, are all at work. There is also a carpenter sawing a piece of wood, and two blacksmiths beating a piece of iron, the one using a sledge, and the other a small hammer; a boy turning a grindstone, while a man grinds an instrument upon it; and a barber shaving a man, whom he holds fast by the nose with one hand. The boy was only about seventeen years of age when he completed this curious work, and since the bent of his mind could be first marked, his only amusement was that of working with a knife, and making little mechanical figures. This is the more extraordinary, as he had no opportunity whatever of seeing any person employed in a similar way. He was bred a weaver with his father, and since he could be employed at the trade, has had no time for his favourite study, except after the work ceased, or during the intervals; and the only tool he ever had to assist him was a pocket-knife. In his earlier years he produced several curiosities on a smaller scale; but the one now described is his greatest work, to which he devoted all his spare time during two years."

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THE AMSTERDAM PILE.

In an interesting report on the "Waterstaat" of the Netherlands, presented to the British Government, we read: "To appreciate the beauty of the Dutch science of hydrodynamics, it is necessary to understand that, from first to last, it is a question of comparative levels. The error of a centimètre in level might drown a province, or frustrate the purpose for which some canal had been designed. Thus it may be said, without exaggeration, that the most important institution in the kingdom of the Netherlands is a certain antiquated pile at Amsterdam--but one of many million pine-trees brought from Norway, on which the city is perched,--which indicates the rise and fall of the outer waters of the Zuyder Zee and German Ocean. For 200 years this pile has been watched with anxiety by the burghers of the Netherlands, and a graduated scale has been marked upon it, in which the mean water level is represented by zero. It is known as the 'Amsterdamsche Peil,' and every hydraulic undertaking in the country is measured by its standard, as having a level of so many mètres or centimètres above or below the usual level of the sea. The initials A. P. (Amsterdamsche Peil), O. A. (Zero of Amsterdam), or Z. P. (Zero of Pile), are the forms of abbreviation most generally used to represent the starting-point in all hydraulic calculations; and one of these, with the signs + and -, must therefore necessarily occur in every intelligible description of Dutch public works."

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THE PERILS OF EXPERIMENT.

M. Rouelle, an eminent French chemist, was not the most cautious of operators. One day, while performing some experiments, he said to his auditors: "Gentlemen, you see this cauldron upon the brazier; well, if I were to cease stirring for one moment, an explosion would ensue, that would blow us all into the air." The audience had scarce had time to reflect on this comfortable piece of information, when the operator actually did forget to stir, and his prediction was amply verified. The explosion took place with a terrible crash; all the windows of the laboratory were smashed to pieces, and two hundred auditors were whirled away into the garden. Fortunately, no one received any serious injury, the chief violence of the explosion having been in the direction of the chimney. The demonstrator himself marvellously escaped without further harm than the loss of his wig.--A certain Scotch Professor--not of the present generation--as remarkable for the felicity of his experimentation as Rouelle could be for his failures, was once performing an experiment with some combustible materials, when the mixture exploded, and the phial which he held in his hand flew into a thousand pieces. "Gentlemen," said the Doctor to his students, with the most unaffected gravity, "I can assure you that I have performed this experiment often with the same phial, and never knew it break in my hands before." The simplicity of this somewhat superfluous assurance gave rise to a general laugh, in which the Professor, instantly discerning the cause of it in his own excellent Irishism, most heartily joined.

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THE SIBERIAN MAMMOTH REMAINS.

About 40,000 lbs. of fossil ivory--that is to say, the tusks of at least 100 Mammoths--are bartered for every year in New Siberia, so that in a period of 200 years of trade with that country, the tusks of 20,000 Mammoths must have been disposed of--perhaps even twice that number, since only 200 lbs. of ivory is calculated as the average weight produced by one pair of tusks. As many as ten of these tusks have been found lying together, weighing from 150 to 300 lbs. each. The largest are rarely sent out of the country, many of them being too rotten to be made use of, while others are so large that they cannot be carried away, and are sawn up in blocks or slabs on the spot with very considerable waste, so that the loss of weight in the produce of a tusk before the ivory comes to market is of no trifling amount. A large portion of this ivory is used by the nomad tribes in their sledges, arms, and household implements, and formerly a great quantity used to be exported to China; a trade which can be traced back to a very distant period. Notwithstanding the enormous amount already carried away, the stores of fossil ivory do not appear to diminish; in many places near the mouths of the great rivers flowing into the Arctic Ocean, the bones and tusks of these antediluvian pachyderms lie scattered about like the relics of a ploughed-up battlefield, while in other parts these creatures of a former world seem to have huddled together in herds for protection against the sudden destruction that befell them, since their remains are found lying together in heaps. In 1821, a hunter from Yakutsk, on the Lena, found in the New Siberian Islands alone 500 poods (18,000 lbs. English) of Mammoth tusks, none of which weighed more than 3 poods; and this, notwithstanding that another hunter on a previous visit in 1809 had brought away with him 250 poods of ivory from the same islands. Entire mammoths have occasionally been discovered, not only with the skin (which was protected with a double covering of hair and wool) entire, but with the fleshy portions of the body in such a state of preservation that they have afforded food to dogs and wild beasts in the neighbourhood of the places where they were found. They appear to have been suddenly enveloped in ice, or to have sunk into mud which was on the point of congealing, and which, before the process of decay could commence, froze around the bodies, and has preserved them up to the present time in the condition in which they perished. It is thus they are occasionally found when a landslip occurs in the frozen soil of the Siberian coast, which never thaws, even during the greatest heat of the summer, to a depth of more than 2 feet; and in this way, within a period of a century and a half, five or six of these curious corpses have come to light from their icy graves. A very perfect specimen of the Mammoth in this state was discovered in the autumn of 1865, near the mouth of the Jenissei; an expedition was despatched to the spot by the Imperial Academy of Sciences in the summer of 1866, and the result of that expedition, it is considered, will be the disclosure of some interesting facts in the natural history of a former creation.--_Mr. Lumley's Report on Russian Trade._

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VELOCITY OF ELECTRICITY.

One of our most profound electricians is reported to have exclaimed, "Give me but an unlimited length of wire, with a small battery, and I will girdle the universe with a sentence in forty minutes." Yet this is no vain boast; for so rapid is the transit of the electric current along the lines of the telegraph wire, that, supposing it were possible to carry the wires eight times round the earth, it would but occupy _one second of time_. The immense velocity of electricity makes it impossible to calculate it by direct observation; it would require to be many thousands of leagues long before the result could be expressed in the fractions of a second. Yet Professor Wheatstone devised some apparatus for this purpose, among which was a double metallic mirror, to which he gave a velocity of eight hundred revolutions in a second of time. The Professor concluded, from his experiments with this apparatus, that the velocity of electricity through a copper wire, one-fifteenth of an inch thick, exceeds the velocity of light across the planetary spaces; that it is at least 288,000 miles per second. The Professor adds, that the light of electricity, in a state of great intensity, does not last the millionth part of a second; but that the eye is capable of distinctly perceiving objects which present themselves for this short space of time.

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MONOCHROMATIC PAINTING.