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the salaries of the masters, is stated in the Government Report not to exceed 1200l. per annum. The collegiate salaries are 391. 6s. 8d. to the upper, and 157. to the under master, with houses for their residence. What they receive individually from the scholars for instruction, is a remuneration apart, with which the church has no concern. The annual payment to the masters is different in different years. It is thirteen guineas the It is thirteen guineas the first year, whether for a town boy or king's scholar, ten guineas the next two years, and eight guineas the last year. The assistant masters are not of collegiate institution, and are proportioned to the state of the school: their incomes also arise from the scholars, for of the thirteen guineas paid for education, six go to the masters, and the rest to different ushers. Boarding-houses are provided for the accommodation of the town boys. There are five of these, in each of which an usher resides and superintends the inmates. Further particulars concerning this celebrated institution will be given in a second notice.

OLD ENGLISH NAVIGATORS. CAPTAIN JOHN DAVIS.

I.

In the year 1585, "certaine honourable personages and worthy gentlemen of the court and country, with divers worshipful merchants of London and of the west countrey, mooved with desire to advance God's glory, and to seek the good of their native countrey, consulting together of the likelihood of the discovery of the north-west passage, which heretofore had bene attempted, but unhappily given over by accidents unlooked for, which turned the enterprisers from their principall purpose, resolved, after good deliberation, to put downe the adventures to provide for the necessarie shipping, and a fit man to be chief conductour of this so hard an enterprise." According to Hakluyt, (whose authority we follow in the present narration,) the most active merchant of the company was William Sanderson, who, "besides his travaile, which was not small, became the greatest adventurer with his purse, and commended unto the rest of the company one Mr. John Davis, a man very well grounded in the principles of the arte of navigation, for captaine and chief pilot of this exploit."

This celebrated navigator was born at Sandridge, in the parish of Stoke Gabriel, near Dartmouth, in Devonshire. His residence near that sea-port probably excited his taste for the life of a seaman. Accordingly, at an early age, he went to sea, and with the assistance of a good master, and his own skill and industry, he soon became one of the ablest navigators of his time. Being furnished by the London merchants with two small barks, "the Sunneshine of London and the Mooneshine of Dartmouth," of fifty and thirty-five tons respectively, Davis departed from Dartmouth on the 7th of June. After experiencing, as usual, some delays from contrary winds, they came, on the 19th of July, to the sixtieth degree of north latitude; and in a very calm sea, they heard "a mighty great roaring, as if it had been the beach of some shore;" the fog being great, and fearful of running suddenly upon land, they sounded, but found no ground at three hundred fathoms : the captain then proceeded in a boat towards this supposed beach, and was soon encompassed by numerous icebergs, and greatly astonished to find that the noise was occasioned only by the rolling of the ice together. Davis broke off some pieces of the ice, which, being carried to the ship, were converted into good water. On the next day they discovered the southern coast of Greenland, "the most deformed, rockie, and mountainous land that ever we saw; the first sight whereof did show as if it had bene in forme of a sugar-loafe, standing to our sighte above the cloudes, for that it did showe

over the fogge like a white liste in the skie, the tops altogether covered with snow, and the shoare beset with ice a league off into the sea, making such irksome noise, as that it seemed to be the true pattern of desolation, and after the same our captain named it The Land of Desolation.'" Perceiving that they were run into a very deep bay, wherein they were almost surrounded with ice, they kept coasting along the edge of it, southsouth-west, till the 25th, when they discovered that the shore lay directly north. They therefore altered their course to the north-west, in hopes of finding the desired passage; but, on the 29th, they discovered land to the north-east, in latitude 64° 15'. On approaching the coast, (which, however, was still Greenland,) they found some good roads for shipping, and many inlets in the land, whereby they judged this land to be a number of islands standing together. Having landed upon a small island, they discovered some tokens of inhabitants, for they found "a small shoo, and pieces of leather sewed with sinews, and a piece of fur and wool like to beaver." They then proceeded to another island, and having ascended an eminence, the people of the country espied them, and made a lamentable noise like the howling of wolves. In order to get on friendly terms with these people, Davis sent for his musicians, and caused them to play while a part of the crew danced. The natives gradually approached in their canoes, near enough to talk," their pronunciation was very hollow through the throat." At length one of them, pointing to the sun, "would presently strike his breast so hard, that we might heare the blow. This he did many times before he would any way trust us. Then John Ellis, the master of the Mooneshine, was appointed to use his best policie to gaine their friendship; who strooke his breast, and pointed to the cunne after their order; which, when he had divers times done, they beganne to trust him, and one of them came on shoare, to whom we threw our cappes, stockings, and gloves, and such other things as then we had about us, playing with our musicke, and making signes of joy, and dancing. So the night comming, we bade them farewell, and went aboord our barks."

The next day no less than thirty-seven canoes were in motion about the ships, the natives calling to the sailors to go ashore; but not being in a hurry to do so, one of the natives ascended a rock, and jumped and danced, displaying a seal's skin, and making a noise on a sort of timbrel, which he struck with a stick. Whereupon Davis, having ordered the boats to be manned, rowed up to them; and having mutually pointed, with certain gestures, to the sun, a great confidence arose, and barter proceeded briskly. "We bought five canoes of them; we bought their cloathes from their backs, which were all made of seale's skinnes and bird's skinnes; their buskins, their hose, their gloves, all being commonly sowed and well dressed; so that we were fully perswaded that they have divers artificers among them. We had a paire of buskins of them full of fine wooll, like beaver. Their apparell for heat was made of bird's skinnes, with their feathers on them. We saw among them leather dressed like glover's leather, and thick thongs like white leather of a good length. We had of their darts and oares, and found in them that they would by no means displease us; but would give us whatsoever we asked of them, and would be satisfied with whatsoever we gave them. They took great care one others would come and carry him away between them that of another; for when we had bought their boats, then two had sold us his. They are very tractable people, void of craft or double dealing, and easy to be brought to any civility or good order; but we judge them to be idolators, and to worship the sunne."

The natives promised to return next day with a quantity of furs and skins, which they saw were highly valued by the foreigners; but a favourable breeze arising, and Davis having understood by signs from these people that there was a great sea towards the north and west, proceeded on his voyage. He steered

This

Fig. 1.

ECHINI, OR SEA-EGGS.
I.

across the strait which bears his name, and on the 6th of August found land in latitude 66° 40', quite free from "the pester of ice," and anchored in a safe road under a great mountain, of which the cliffs were as WHILE many of the zoophyte inhabitants of the ocean "orient as gold." This mountain he named Mount take the form of branches, leaves, and flowers, there are Raleigh; the road where their ships lay at anchor, vast numbers which have been popularly named seaTotnes Road; the bay which encompassed the mouneggs, and sea-stars. The former of these we are now tain, Exeter Sound; the fore-land towards the north, about to describe. The Echini, or Sea-eggs, as they Dier's Cape; and that towards the south, Cape Wal-exist in the ocean, are animals having a calcareous shell singham. While at anchor, the seamen saw three of a roundish, oval, or conical figure, and mostly covered white animals, which seemed to be goats. Anxious to with moveable prickles. While bristling with these procure fresh victuals and some sport, they gave chace, prickles or spines, the animal is called sea-urchin, or but discovered, not goats, but enormous white bears. sea-hedgehog; but when these fall off, the shell is more The animals rushed on furious and fearless, till, being animals is so great, that to describe their various forms, commonly known as a sea-egg. The variety in these received with several balls, they retreated, apparently not much hurt, but were pursued, and at length killed. certain genera have been named turbans, diadems, merThey appeared to have fed on nothing but grass; it maid's skulls, or hearts, or fairy stones. was, however, necessary to remove large quantities of fat before the flesh could be eaten. On the 8th of August he left this place, and coasting for some days, arrived at the cape which he had before reached. promontory he named "The Cape of God's mercy," as being the place of their first entrance for the discovery. Turning this cape, they came to a very fine strait or passage, twenty or thirty leagues broad, free from ice, and the water apparently the same as in the ocean. This passage still retains the name of its discoverer,"Davis's Straits." Having ascended about sixty leagues along this strait, they discovered several islands in the mid-channel, on some of which they landed: the coast was very barren, without wood or grass, and the rocks were like fine marble, veined with different colours. On one of these islands the seamen heard the howl of dogs, and saw a number approach, of wolfish appearance, but apparently peaceably disposed. Impressed with the idea that on these shores animals of prey were only to be found, they fired, and killed two; round the neck of one of which they found a collar, and soon afterwards discovered the sledge to which he had been yoked. Although the islands in this sound were numerous, yet the passage was open, and the hopes of our navigators were daily increased, that, by pursuing this track, the north-west passage might be discovered; but about the 20th of August, the wind appearing to settle in a contrary direction, and dreading the approach of winter, they determined to return home. After a safe passage, they reached Dartmouth on the 29th of September.

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DESCRIPTION OF A FOLIO.

THAT weight of wood, with leathern coat o'erlaid;
Those ample clasps, of solid metal made;
The close-prost leaves, unclosed for many an age,
The dull red edging of the well-fill'd page;
On the broad back the stubborn ridges roll'd,
Where yet the title stands in tarnish'd goid:
These all a sage and labour'd work proclaim,
A painful candidate for lasting fame:
No idle wit, no trifling verse can lurk
In the deep bosom of that mighty work;
No playful thoughts degrade the solemn style,
Nor one light sentence claims a kindred smile.
Hence, in these times, untouch'd the pages lie,
And slumber out their immortality.
They had their day, when, after all his toil,
His morning study, and his midnight oil,
At length an author's ONE great work appear'd,
By patient hope, and length of days, endear'd;
Expecting nations hail'd it from the press;
Poetic friends prefix'd each kind address;
Princes and kings received the pond'rous gift,
And ladies read the work they could not lift.-CRABBE.

NEVER talk of your schemes before they are executed; lest, if you fail to accomplish them, you be exposed to the double mortification of disappointment and ridicule,

THE COMMON ECHINUS, (Echinus esculentus,) covered with its spines.

The common echinus may be taken as the type of this curious order of animals, although, from the variations in the several genera, the description of one species cannot be fully applicable to others. The excellent description of this animal given in the article on Zoophytes, in the Encyclopædia Britannica, furnishes us with materials for the following notice. The shell of the common echinus is of a globular figure, with a flattened base, formed of ten plates, united by ten others, and all proceeding from the rim of an aperture in the base, and rising upwards. These plates converge towards the top, and are united in a circle opposite the mouth, by a series of small plates. The first series of plates is called area, by Linnæus, and those by which they are joined together, and which are all narrow, and of the same size, he named the ambulacra, from a fancied resemblance to the walks between the parterres of a garden, laid out after the olden fashion. Tubercles of different sizes cover these area, and on a close examination, it will be seen, that a zig-zag line divides each area into two equal parts, composed of numerous long hexagons set in cross rows, and dove-tailed into each other with the most perfect accuracy. The tubercles, with which the shell is thickly studded, support the spines or bristles which are so remarkable in the animal. These move on a pearly globular pivot that sinks into a corresponding cup in the base of the spine, and are retained in their place by the soft epidermis or skin that covers the whole of the shell in its fresh condition. The primary spines are frequently large in proportion to the shell, but with these are generally intermingled smaller ones of three descriptions, i. e., spines of the same form as the primary ones, but much smaller; others, slender as a hair, but dilated into a club at each end; and a third kind on a flexible stalk, supporting three moveable prongs placed in a triangle. The functions of these last are unknown, and they have been mistaken for parasitical animals infesting the echinus. The ambulacra have no spines, but are perforated from top to bottom with holes, arranged in a regular pattern. From these holes are protruded slender fleshy tubes, with

suckers at the end, which aid the animal in its progressive motion.

The mouth of this animal is armed with a most complex apparatus of calcareous jaws, arches, and teeth, consisting of twenty-five separate pieces. For the movement of these parts separate muscles are provided, of which the anatomy has been minutely described by Cuvier. In the shells of the echini which are cast on shore, this frame-work is often found entire in the inside of the case, and Aristotle having found in it a resemblance to a lantern, it has therefore been called "the lantern of Aristotle." But there are other echini which are entirely destitute of this apparatus, being without teeth, and having at the mouth only a narrow transverse slit. From this variation of form, it is natural to suppose that the food of the different species of echinus is also various. Mr. Kirby, speaking of the common echini, informs us, that their station is often near the shore upon submerged ledges of rocks, and tha they feed upon whatever animals they can seize, sometimes turning upon their back and sides, and sometimes moving horizontally. "This enables them more readily to secure their food, with the aid of the numerous suckers in the vicinity of their mouth, which, when once they are fixed, never let go their hold till the animal is brought within the action of their powerful jaws. Lamarck thinks that they do not masticate, but only lacerate their food; but as two faces of each of their pyramidal organs answer those of the two adjoining ones, and these faces are finely and transversely furrowed, this looks like masticating surfaces. Bose, who appears to have seen them take their food, says it consists principally of young shell-fish and small crustaceous animals. As the latter are very alert in their motions, it is difficult for the sea-urchins to lay hold of them; but when once one of these animals suffers itself to be touched by one or two of the tentacles of its enemy, it is soon seized by a great number of others, and immediately carried towards the mouth, the apparatus of which developing itself soon reduces it to a pulp."

The development of the echini from the time of their first leaving the egg, has not come within the observation of any naturalist, but the young of Echinus esculentus has been examined when only one-eighth of an inch in diameter, and found to have the form and armature of the full-grown animal. The prickles were toothed along their edges; but those spines which in the perfect state have three prongs, as already described, were only provided with two. The globular form was perfect in the young animal; but the shell was composed of few pieces. It may appear contrary to the general law which regulates the mode of increase in these animals, that the shell should be thus perfectly formed in miniature, for it appears necessary whenever cells, intended for the lodgment of soft organs, are to be formed of hard materials, that the foundation should be laid upon a scale suited to the after-growth of the animal, otherwise the soft parts within would be so confined and contracted that they must cease to grow altogether. But in the case of the echini, provision is made for the expansion of the shell itself, for each shell is divided into a number of small pieces, and each piece has that polygonal form which is best suited to the perfect junction of the whole. Small additions are therefore constantly being made to the margins of each of these polygonal pieces, and the expansion goes on exactly in proportion to the growth of the soft parts of the animal within.

The roe of this animal occupies much space within the shell, being very large in proportion to the animal and its other viscera; and it is in the spring, when the roe is fully developed, that this animal is in some places used as food, as its name imports. An old writer speaks of the sea-egg, as being eaten by the poor in many parts of England, and by the better sort abroad. It is recorded that these animals formed one of the favourite dishes among the Greeks and Romans. "They were dressed with vinegar, honied wine, or mead, parsley, and mint; and esteemed to agree with the stomach. They

were the first dish in the famous supper of Lentullus, when he made Flamen Martialis priest of Mars. By some of the concomitant dishes they seemed designed as a whet for the second course to the holy personages, priests, and vestals invited on the occasion." They are also mentioned at the marriage feast of Hebe. 6 Thither came crabs and urchins, unable to swim in the sea, but travelling only on the ground." In the Wasps of Aristophanes, likewise, the hero of the piece repeats a fable respecting an urchin, who, when his shell had been cracked by a woman, summoned witnesses to prove the assault. He is interrupted by the remark, that it would have been wiser of the animal to buy a bandage than to spend his time in proving the assault. Horace mentions the echinus several times as very good eating.

The seas of warm and tropical countries are the most productive of these animals; but notwithstanding the number of living species, the fossil remains very far exceed them. These are found principally in the chalk and oolite formations, and are so abundant, and so well preserved, that there are few collections of fossils in which we may not meet with numerous specimens.

The empty shells of the echini are sometimes found in considerable numbers on our western coasts, especially after the Atlantic has been much agitated by storms. They are shaped more like an apple than an egg, having a small aperture at the top, and another at the opposite extremity. In this state the projecting suckers, spines, and bristles, have all been broken off, leaving the minute apertures reaching from one end to the other in regular rows, something in the same manner as the meridians of a globe.

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METALLOCHROMY, OR THE ART OF

COLOURING METALS.

Ir is generally supposed that the blue colour imparted to steel, results from a thin film of oxide formed upon the surface of the metal when exposed to a certain temperature. About fifteen years ago, Professor Nobili, of Reggio, offered a new explanation of this fact, and discovered a method of imparting colour to metallic surfaces: as his results are extremely beautiful and varied, a brief notice of them may be acceptable.

The following is one of the principal experiments connected with what the inventor appropriately terms the Art of Metallochromy. A plate of platinum is placed horizontally at the bottom of a glass or china vessel. A platinum point is suspended vertically over this, in such a manner, that the distance between the point and the plate may be about half a line. A solution of acetate of lead is next poured into the vessel, so as not only to cover the plate, but to rise two or three lines higher than the point. The plate and the point are now brought into communication, the former with the positive, and the latter with the negative pole of a voltaic battery. At the moment when the voltaic circuit is closed, a series of coloured rings appear on the surface of the plate precisely under the point. These rings are similar to those described as Newton's rings in our Philosophy of a Soap-bubble*, but in an inverse order: Newton's rings begin at the centre; Nobili's at the circumference, where, from the nature of the electrochemical process, the thinnest layers are deposited: the thickest layers are evidently those at the centre.

The

This fact, which could not fail to strike any one observing it for the first time, led to the discovery of others. "Science never consults its interests so truly," remarks Professor Nobili, "as when it aims at some useful object connected with the arts." He foresaw the advantages the arts were likely to derive from this new method of colouring metals, and attended seriously to its application. His object was, instead of producing rings of various colours upon a plate of metal, to cover its surface uniformly with any desired tint. colours being obtained by the effect of very thin plates applied to the surface of metals, it is easy to conceive how difficult it was to preserve such plates of a uniform thickness over the whole of an extensive surface. "Great, however, as the difficulties were, I thought I owed it both to art and to science, to do my utmost to surmount them. I thought it due to art, because this would be extended by means of the uniformity of the tints; and to science, because in the tints produced by plates of a particular thickness, the experimental philosopher would find the means of investigating, with peculiar advantage, the nature and properties of colours."

By substituting plates for the platinum point which forms the coloured rings, it was found that a surface of metal could be covered with one uniform tint. In 1828, Professor Nobili presented several such productions to the French Institute, and afterwards to our Royal Society, and particular attention was excited by the beauty and vividness of the tints, the precision of the outlines, and the softness of their blendings.

has designated by the epithet chromatic. This scale consists of forty-four tints, each of which is applied to a plate of steel. The tints are disposed in the same order as the layers or films by which they are produced: the colour of the thinnest film is placed first, and the others follow in the order of the progressively increasing thickness of the plates. In this arrangement the layers or films which produce the several colours are all applied by the same electro-chemical process. The voltaic bat tery, the solution of acetate of lead, the distances, all remain exactly the same. There is nothing variable but the duration of the action, which, in respect to the layer No. 1, is very short, a little longer in respect to the second, and increases progressively from the lowest to the highest number.

44. Rose lake

CHROMATIC SCALE.

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The effect produced by these tints, when disposed in the above order, baffles description; it bears a resemblance, however, to that produced on the ear by a scale of semitones, executed by a perfect voice. "I have shown my scale to several, and especially to those erudite visit at Reggio. In all it excited but one feeling of delight. and learned persons who have favoured me with a passing

Although the efforts of this ingenious philosopher were attended with complete success, his methods so easy So gradual, indeed, is the transition from one tint to anoin their practical application, and the results so beauti-ther, and such the harmony with which they are blended, ful; although, too, the attention of scientific men was that if the eye be accidentally turned away, it reverts in a directed to the subject, it is remarkable that this new moment, as if moved by an irresistible desire to gaze still art was practised by its inventor only up to the time of longer on the display. This statement is no exaggeration. his death, since which it appears to have been quite for- It is but the mere fact, in respect to which a language much gotten. Not only would this art be valuable to workers more glowing would be perfectly consistent with truth; so in metal generally, but the artist would find in it a wide overpowering is the charm which, if I may use the expresfield for observation and study. Professor Nobili has sion, pervades the scale of our coloured plates." arranged the tints produced by his method in their natural order, so as to form a scale, or gamut, which he

• See Saturday Magazine, Vol. XV., pp. 199, 204, 222, and 231.

In an admirable memoir, (which has been translated into the first volume of TAYLOR's Scientific Memoirs,) Professor Nobili examines and compares with natural phenomena all the colours which compose his chromatic

scale. If the reader be at all interested in the subject
of colour, either artistically or scientifically, we strongly
recommend him to study this memoir. As we are
about to inform the reader of an easy method of pro-
ducing these beautiful colours, we can find space for
only a few short extracts. This we do the more readily
because in our notices of the Soap Bubble, already re-
ferred to, a popular account is given of the principles
upon which colour is produced by thin plates or films.
The colours which the clouds assume, are, in general,

Black, or very pure ash-colour;
White, or very light ash-colour;
The colour of smoke or coffee;
Red, more or less fiery;

Blue, very deep, and sometimes approaching to violet. These are exactly the tints that would constitute the first ring, were we to include in it the first two colours of the second ring. The tints of smoke result from the more or less thorough blending of the blond and the tawny; those of fire from Nos. 8, 9, and 10; the deep blue is produced by the Nos. 10, 11, and 12, which are the deepest tints of the scale.

The first blond is properly that of light hair in childhood, and it is a fact worthy of remark, that as children grow older, it becomes progressively deeper and deeper, in the order of the Nos. 2, 3, and 4, in the scale. The perfect resemblance of the first tints on the scale to those which we observe about the moon when she is surrounded by clouds, is equally remarkable; it seems in fact that this luminous appearance may be thus definitively explained. Tints of this kind do not arise from refraction and diffraction, they are produced only by means of thin plates; the luminous halo seen round the moon when overcast with fog or light clouds, is therefore a phenomenon produced by thin plates.

This observation, combined with the fact, that the tints exhibited by the clouds in every variety of aspect, are almost all comprised in the first ring, leads to another consequence relative to the constitution of vesicular vapours. The measurements and experiments of Newton have shown what are the dimensions of the layers of air, of water, and of glass, which produce the colours of the several rings. The red of No. 10, is the last tint of the first ring; the indigo, No. 12, belongs to the second; and the thickness of the layer of water, which produces it by reflection, is about the ten-millionth part of an English inch. As we know then, on the one hand, that the vesicular vapours are formed of water, and on the other, that they do not reflect or transmit any tint beyond No. 12; we may conclude, that their external film is in no case thicker than the tenmillionth part of an inch.

This result appears to Professor Nobili so decidedly certain as to be entitled to a place in science.

In speaking of the tints of the second ring, he says, We have the sky, their type in nature, constantly before our eyes; for who is there that knows not the dawn," with rosy forehead and golden feet"? Beginning with No. 12 of the scale, let us run our eye over it as far as No. 28, and we shall find that the tints of the sky are disposed there in the order in which they present themselves in the magnificent spectacle of the dawning day. This succession, as we have already observed, is the most beautiful of all: Newton's second ring gives no idea of it, because its colours are not, and cannot be, sufficiently developed to produce the effect. Painters, if I mistake not, will do well to avail themselves of this part of the scale; they will find it a faithful copy of the beautiful tints of the morning, and endeavour to transfer them to their compositions. Natural philosophers will not fail to remark, that among the various tints of the sky there is no trace of green. This would heretofore have been found a perplexing circumstance, but it may now be satisfactorily explained, merely by reflecting that the tints of the sky belong to the second order, in which also there is no tinge of green. From the blue to the yellow, the transition is through a very faint gradation of azure-yellow, and this is observed to be exactly the case in nature.

The tints produced by the vapours and clouds belong to the second order. They contain in general more fire than the natural tints of the sky, but this quality is nothing in comparison with the purity, vividness, and variety, displayed in the tints of the second order. The appearance of the sun is never so magnificent as when the air is perfectly pure. Toward evening the lower regions of the atmosphere

are always more or less charged with vapours, the air no longer retains its morning transparency, and the setting of the sun is attended by a fiery tint, which greatly mars the that we are to attribute the inflamed appearance of the sky, tranquil beauty of the spectacle. It is to those vapours the first order, and those are of that fiery cast. Were it not because they possess the power of transmitting the tints of for this circumstance, the setting of the sun might justly vie with its rising.

Philosophers had long since settled their opinions as to the colours of the sky. These they explained by assigning to the air the property of reflecting the higher colours of the spectrum, (violet, indigo, &c.,) and that of transmitting the lower, (red, orange, &c.) The explanation was correct, so far as it went, but to make it complete the exact quality of the tints should be determined by indicating the order to which they belong. It was necessary also to ascertain how light is affected by the presence of vapours. The considerations which we have just stated will perhaps supply both these deficiencies.

A singular property is connected with some of the tints of the scale. If a drop of alcohol is let fall on immediately above and below this No.,) and spread so the violet, No. 11, (as also upon a few other tints as to cover part of the colour, the part thus made wet is no longer the same; we see instead of it a feeble tint resembling that of coffee mixed with milk; but the other part remains unchanged. The comparison can be made instantaneously, and the difference between the two tints is so striking, that we are at a loss to conceive how a transparent and very limpid film of alcohol can produce such a change in the violet colour on which it is placed. The alcohol gradually evaporates, and the colour recovers its former brilliancy. Water, oil, and the different saline solutions, produce the same effect.

The prismatic colours produced on steel and copper by the action of fire, and the colours exhibited by tin, bismuth, lead, &c., when in a state of fusion, have been supposed to result from the oxidation of those metals. This explanation may reasonably be doubted. The blue or violet colour which is sometimes given to steel is to secure it from rust. This colour is produced by means of fire in the process of giving steel a particular temper --a temper which is called violet, because it is produced simultaneously with the colour. If this tint were the effect of oxidation, would it not rather accelerate than prevent oxidation? A very high degree of polish will keep off rust for a long time, but cannot stop it when once the action has commenced.

According to Professor Nobili the colours of which we now speak belong to the same class as those produced by tin plates, and he concludes that no oxide is formed upon the surface of the steel, because, 1st, the metal retains, beneath the deposited layer, its natural brilliancy; 2nd, this layer produces the phenomenon of the coloured rings in all its beauty; and 3rd, instead of oxidizing or rusting the metal, the coloured film contributes to secure it against rust in every part to which it is applied, as was proved by exposing two steel plates, one only of them being coloured, in the open air, to all the vicissitudes of a rainy autumn; when at the end of a month the uncoloured plate was all rusted, the other had lost a little of its colour, but was free from rust.

Considering then, that by the electro-chemical means stated at the beginning of this article, the films can be deposited with equal facility upon platinum, a metal difficult to be oxidized, as upon iron and steel, which belong to a class of metals most easily oxidized, as well as from the results of numerous collateral experiments, it appears that oxygen and certain acids may adhere to the surfaces of metals without producing the slightest chemical change in them. It may be laid down as a general proposition, that the oxygen of the atmosphere produces the colours on metals by the action of fire, not, as is supposed, by oxidizing the surface of the metal, but, by becoming fixed in the form of a thin plate, or film, similar to those produced by the electro-chemical process.

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