The majority of the essays in which these discoveries were made known, are of too limited and technical a character to admit of notice in the pages of our journal. There is one of them, however, that, on a process by which platina may be render-rature along with active re-agents, as, for ed malleable,' which cannot be dismissed without a word of explanation.

Among other bodies which the alchemists of the middle ages thought it possible to It was at this crisis that Wollaston came discover, and accordingly sought after, was forward to put a new weapon into the hands a Universal Solvent, or Alkahest as they of the chemical analyst. Several years benamed it. This imaginary fluid was to fore he turned his attention to the subject, possess the power of dissolving every sub- scattered grains of a brilliant metal had stance, whatever its nature, and to reduce been found in the sands of certain of the all kinds of matter to the liquid form. It South American rivers. To this, from its does not seem to have occurred to these resemblance to silver, or in their language ingenious dreamers to consider, that what Plata, the Spaniards gave the name of Pla

tina, or little silver. This metal was found tinate its particles, and convert it into a to resist the action of nearly every substance solid ingot. This ingot or bar could then except Aqua Regia; to suffer no change, be flattened into leaf, drawn into wire, or nor to become rusted by protracted expo- submitted to any of the processes by which sure to the atmosphere; and to be perfectly the most ductile metals are wrought. infusible by the most powerful forge or fur

nace.

We have passed over unnoticed many practical minutiæ essential to the success Here then was a substance for the chem- of Wollaston's process. The reader is ist's crucible, could a method of working more concerned to know that the platina it only be discovered. But the very pro- crucible has been one of the chief causes of perties which made its value certain, if it the rapid improvement which chemistry has were wrought into vessels, forbade its being recently undergone, and that it is an indiseasily fashioned into them. It occurred in pensable instrument in the laboratory. The nature only in small grains which could not costliness of the metal has not forbidden be melted, so that it was impossible, as with its application to manufacturing operations most other metals, to covert it into utensils even on the largest scale. In the oil of vitby fusion. Neither was it possible by ham- riol works, stills of platina are made use of mering to consolidate the grains into con- for distilling sulphuric acid, each of which, siderable masses, so that vessels could be though holding only a few gallons, costs beaten out of them, for the crude metal is above a thousand pounds. A coinage of very impure. Accordingly, it happened, platina was introduced into the Russian dothat for years after the value of platina had minions, which possess valuable supplies of been discovered, it could not be turned to its ores; but though roubles and other coins account. Whole cargoes of the native struck in it, occasionally reach this country metal, although it is now six times more as curiosities, we understand that the coincostly than silver, are said to have lain un-age has been withdrawn by the imperial gopurchased for years in London, before Wol-vernment, in consequence of the fluctualaston devised his method of working it.

That method was founded upon the property which platina possesses of agglutinating at a high temperature, though not melted, in the way iron does, so that, like that metal, it can be welded, and different pieces forged into one. This property could not, however, be directly applied to the native grains owing to their impurity and irregularity in form.

Wollaston commenced by dissolving the metal in aqua regia; purified it whilst in solution from the greater number of accompanying substances which alloyed it; and then, by the addition of sal ammoniac, precipitated it as an insoluble compound with chlorine and muriate of ammonia. When this compound was heated, these bodies were dissipated in vapor, and left the platina in the state of a fine black powder, which was further purified by washing with

water.

It was only further necessary to fill a proper mould with this powder well moistened, and to subject it to powerful compression. By this process the powder cohered into a tolerably solid mass, which was gently heated by a charcoal fire, so as to expel the moisture and give it greater tena city, It was afterwards subjected to the intensest heat of a wind furnace, and hammered while hot, so as completely to agglu

tions that occur in the value of the metal. In our own country, from the great consumption of platina in chemical processes, its value has rapidly risen even within the last few months; but it is constantly shifting. Nothing but its rarity and costliness prevent its application to the construction of every kind of culinary vessel, for which its purity, cleanliness, and enduringness especially fit it. A thousand other uses would be found for it, if it were more abundant.

Were it now the custom to honor men after death according to the fashion of the Greeks and Romans, Wollaston's ashes would be consigned to a gigantic platina crucible, as to a befitting and imperishable sepulchral urn.

His other chemical papers are all important. One of them, 'on the chemical production and agency of electricity,' proved, by singularly ingenious and beautiful experiments, that identity of voltaic and friction electricity, which Faraday has since confirmed by still more decisive trials. The

* Platina costs at present, in the state of ingot or bar, from 30s. to 353. per ounce, wholesale. Manufactured articles from 32s. to 42s. per ounce, also wholesale. The retail prices are from 58. to 10s. higher. Virgin silver sells at 5s. 8d per ounce, wholesale; at 9s. per ounce, retail, when manufactured. Sterling silver is worth 4s. 11d. per ounce.

satiety, seems never to have tired of her rubies and emeralds, or to have grown weary of admiring her family diamonds.'

others had reference chiefly to the atomic theory, which Wollaston was a great means of introducing to the favorable notice of chemists. One was 'On superacid and sub- And if the symbolical, æsthetical, fictiacid salts,' and contained one of the earliest tious and commercial value of crystals has and most convincing proofs which can be been great, their worth to the man of science given of the existence of such a law of has not been small. The mineralogist multiple proportion, as Dalton had an- counts them the most precious treasures of nounced. The other on A synoptical his cabinet. The geologist defines and scale of chemical equivalents,' first brought the laws of combination within the reach of the student and manufacturer.

marks out rocks by them. The electrician has detected curious phenomena by means of their aid. The investigator of the laws Wollaston published three papers on the of heat finds them of indispensable service shapes of crystals, and on the mode of meas- in studying his subject. The optician is uring them. No branch of science is less indebted to them for the greatest generaliinviting to the general student than crystal-zation of his science, and for the discovery lography. Nevertheless, we must be al- of many of its most delightful, though most lowed to refer briefly to one of Wollaston's intricate departments. Recently they have essays on that subject. The most superfi- been declared to present remarkable and cial sketch of the philosopher whose works hitherto unsuspected relations to magnetwe are considering, would be inexcusably defective if it passed it by.

The paper we refer to is entitled, 'Description of a reflective Goniometer,' and, next to that containing the account of the platina process, is perhaps Wollaston's most important contribution to science. It is much more difficult, however, to convey an idea of its value, than it was in the case of that essay.

There are no bodies, perhaps, more interesting to a greater number of persons than crystals. The rarer native ones which we name gems, rank with the precious metals in expressing by the smallest bulk the greatest commercial value. The precious stones have been hallowed in the minds of many from their earliest days, by the terms in which they are alluded to in the Bible. The lavish use made of them in adorning the dress of the Jewish high priest; the manifold references to them in the books of the prophets, and in the more impassioned writings of the old Testament; and most of all the striking and magnificent way in which they are referred to by St. John as types of the glories of the world to come, must satisfy even the most careless reader of the Scriptures, that God has marked them out as emblems of indestructibility, rarity, worth, beauty, and purity. Their appropriateness for this purpose must strike every one. The painter has counted it a triumph of his art to imitate even imperfectly their colors and brilliancy. Poets have all loved to sing of them. Beauty, in every age and clime, barbaric and civilized, however much she has loved caprice in other things, and has complained of ennui and

ism. The chemist considers a knowledge of crystallography absolutely requisite, not merely as enabling him to identify substances without the trouble of analyzing them, but likewise as unfolding analogies of the greatest importance in relation to the classification of chemical compounds. Medical men have discovered that, in many dangerous disorders, crystals show themselves in the fluids of the body, and now study their shapes with the utmost care, as a means of detecting and alleviating disease. Finally, the greatest mathematicians have counted it a worthy occupation to investigate the forms and geometrical relations of crystals. We need only remind our scientific readers of the labors of Huyghens, Young, Fresnel, Arago, Brewster, Sir Wil liam Hamilton of Dublin, Herschel, Mohs, Weiss, Mitscherlich, Faraday, not to mention a multitude of others, to satisfy them that we have not overstated matters. undulatory hypothesis of light, the laws of its double refraction, and those of its polarization, have been suggested or discovered by observations with crystals. The same remark applies to the laws of the radiation and polarization of heat, and with limitations might be extended to other branches of natural philosophy. There is not, indeed, a single physical science which has not an interest in crystallography.

The

From this brief statement it will appear, that nearly every class of scientific men was certain to gain by the invention of an instrument which promised greatly to facilitate, and to render more accurate, the study of crystals. We will not say that the poet, the painter, or the beauty owed Wollaston

any thanks. They did not, at least, imme- squares, and all the angles right angles. diately; but in the end it may appear, and The well known doubly refracting Iceland it would not perhaps be difficult to demon-spar (carbonate of lime) crystallizes in an strate, that they are all gainers by the pro- equally regular and perfect but different gress of science. We return, however, to shape. Its crystals are six-sided, but the the reflective goniometer. faces are rhombs, or resemble the diamond on a pack of cards, and its angles are not right angles. From extended observations on the crystalline shapes of bodies, the important law has been generalized, that'the same chemical compound always assumes, with the utmost precision, the same geometrical form.' This enunciation of the law must be accepted with certain important qualifications and exceptions, which our limits do not permit us to dwell upon. This one point, however, we are anxious to explain: the constancy of form affirmed to exist in crystals does not manifest itself 'in equality of the sides or faces of the figures, but in the equality of the angles.' It is the angle, therefore, and not the face of a crystal, which is important, the latter may vary, the former must not; hence the value of a goniometer, or angle measurer.

A goniometer, as its name implies, (yovia, an angle, uέtoor, a measure,) is an instrument for measuring angles. The appellation, though susceptible, of course, of much wider application, is restricted to an apparatus for measuring the angles of crystals. Different goniometers were in use before Wollaston invented his, but they were comparatively rude, and could only be applied to large crystals. This limitation of their employment was doubly disadvantageous. Many substances can be obtained only in minute crystals. In every case, small crystals are ceteris paribus more perfect than large ones. Wollaston's instrument not only applied to very diminutive crystals, but gave more accurate results the smaller the crystal was, provided only it were visible. It was able to do this from the peculiarity of its principle, which lies in this, that instead of measuring the angle formed by the meeting of two faces of a crystal directly, it measures the angle formed by the meeting of rays of light reflected from them. It requires, in consequence, only that the crystal shall be large enough to have visible faces, and that these shall be sufficiently smooth to reflect light. When Wollaston published the account of his goniometer, he stated as an evidence of its superiority to those previously in use, that whereas a certain angle of Iceland spar was reputed to be of one hundred and four degrees, twenty-eight minutes, forty seconds, it was in reality of one hundred and five degrees.

It cannot but seem surprising that it should be of interest to a mineralogist or chemist, to know that the angle of a crystal is by half a degree greater or smaller than it has been supposed to be. The importance of the observation arises out of the fact, that a great number of substances which assume the solid form affect perfectly regular shapes, or, as we say, crystallize. The figures which they thus present are not inconstant and uncertain, but, within prescribed and narrow limits, are perfectly fixed and invariable Common salt, for example, the greater number of the metals, and many other bodies, when they occur as crystals, show themselves as cubes, or solid six-sided figures, with all the faces

Again, many crystals have the same general shape. A very common form, for example, is an octahedron, or double foursided pyramid, arranged like two Egyptian pyramids placed base to base. But though the general configuration is similar, the angles at which the faces of the pyramids incline towards each other are different in different substances, and distinguish each crystal from all its fellows. Yet the differences in angular inclination, though constant, are often very small; hence the importance of the reflective goniometer, as enabling the observer to detect the slightest difference in angular value between apparently similar crystals. For the trouble of a tedious analysis, and the sacrifice of perhaps a rare substance, we are thus frequently able to substitute the simple device of measuring the angle of its crystals.

The fact has a general interest, also. To the law which the goniometer has discovered, we are indebted for the exquisite symmetry and perfection of shape which make crystals, like flowers, delightful objects merely to gaze at. They may be crushed to fragments, or dissolved in fluids, or liquefied by heat, or dissipated in vapor, but they grow up again like trees from their roots, or flowers from their seeds, and exhibit their old shapes with a fidelity and exactitude of resemblance, which no tree or flower ever showed or can show. We heard much of the restoration of the recumbent

warriors in the Temple church of London, | lead to contradiction and confusion. Crysand still more of the skill shown in piecing talline form is now one of the first things together the broken fragments of the Port- attended to in classifying chemical substanland vase; but all such restorations are ces, and is the basis of most of our attempts poor and faint imitations of the art with to arrange them into groups and natural which nature not only restores but repro- families. duces the works of her chisel.

Were all the crystals in the world reduced to dust, in good time they would each reappear. The painter and the poet would not only find the tints, and play of color, and sparkle, exactly as before, but the mathematician would try in vain to discover the smallest fractional difference in the value of their angles. Unity in variety is the voice of all nature; but in the case of crystals, the unity almost pushes the variety aside.

We cannot delay on this curious subject. Suffice it to say that the announcement by Mitscherlich of the law of isomorphism at once overthrew the prevailing systems of mineralogy, and demanded their complete reconstruction. It changed, also, the aspect of chemistry, and where its influence on that science will end we cannot yet tell.

olite to the settlers in a strange country. By means of it, he has surveyed and mapped out the territory he has won, so that new comers may readily understand the features of the district; and has laid down pathways and roads, along which his successors may securely travel.

It deserves especial notice, but has never obtained it, in histories of the progress of chemistry, that he who, by his gift of the To descend from these speculations, the platina crucible, enabled his brethren to exreader will understand, that as every crys- tend the whole science, and especially to tallizable substance has an unchangeable subject every mineral to analysis, by his form peculiar to itself, the crystalline figure other gift of the reflective goniometer of a body is an important character by showed them how to marshal their discovwhich it may be recognized and identified. eries. The latter instrument has been to But this is the lesser service which the the chemist like a compass-needle or theodreflective goniometer has rendered to science. Early in this century, a great German chemist, Mitscherlich, comparing the results obtained by Wollaston's instrument, with those procured by analysis, in the case of crystalline bodies, discovered a very curious and unexpected law. It appeared, that when substances resemble each other in chemical characters, their crystalline forms are also similar. When the similarity in chemical properties is very great, the shapes become absolutely identical. It is a very singular circumstance, which no one appears to have in the least anticipated, that where two closely allied bodies, such as arsenic and phosphorus, unite with the same third substance, they should produce identical forms when the respective compounds are crystallized. Each face of the One of them is on the interesting and one slopes at the same angle as the same poetical subject of Fairy rings.' Most face of the other. A mould of a crystal of persons in this country must be familiar the one would fit a crystal of the same size with the circles of dark green grass which of the other. A goniometer set at the an- are frequently seen in natural pastures, or gle of the one, would exactly measure the on ground which has long lain unploughed. angle of the other. Such crystals are They are particularly abundant on comnamed isomorphous, a Greek word synony-mons and in sheepwalks, such as the chalkmous with the Latin one, similiform, also made use of.

A mere list of papers is a dull thing, of no interest to those acquainted with the papers themselves, and of little value to those who are not. The reader, however, must bear with us little, whilst we bring briefly before him three other essays by Wollaston; they are all curious, and, besides their intrinsic value, are important as illustrating the versatility of his mind, and the singular accuracy of all his observations.

downs in the south of England. Their dimensions are so great, and they are so symmetrical, and so much darker in color than the surrounding herbage, that they never fail to attract the attention of even the most careless passer-by. These circles a beautiful rural superstition supposes to have been marked out by the feet of faries, whirling