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THE UNIVERSITIES.-V.

CAMBRIDGE.-III.

IN our last article upon this University, we alluded to the fact 31° 45′ E. that the Senate were about to consider the advisability of admitting students to the University who are not members of colleges. The fact that this is intended to diminish the cost of University education makes it necessary that we should notice it rather more fully.

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The scheme which is under consideration provides for the appointment of a board which shall stand to non-collegiate students in the same relation as the college now stands to its own members 12 32W..e., it shall maintain order amongst them, and see that they are 0 E. duly informed as to all that is required of them; to manage all accounts of the fees received, and present them in due time for admission to degrees. In reference to the students themselves, the scheme provides that all laws and regulations at present in force with regard to collegiate students shall apply to the non-collegiate. They shall be entitled to be matriculated, examined, and admitted to degrees in exactly the same way as 10 50 E. others, the officers of the above-mentioned board taking the place of the prælectors and tutors of the colleges. They will have to reside in lodgings, licensed by the present lodging-house syndicate, and be under the government of the present University rules so far as they apply to lodging-houses. The fee on matriculation will be fifteen shillings. At the commencement of every term, each student will pay to the above board the sum of thirty-five shillings. Other University fees will remain the same as for ordinary members of colleges.

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This scheme is to come into operation so soon as the necessary alterations shall, by consent of the Crown, have been made in the University statutes, and it is to be considered experimental until the year 1873, when the University will confirm or abolish the present arrangements.

It is obvious that this scheme will reduce the expense of living at Cambridge to something very little more than that in London or elsewhere. But it must be remembered that no provision for education is included in the above payments. The scheme is not intended to include this, but to enable poor students, and students of special subjects, to curtail their social expenses as much as they please. As such, the scheme is deserving of every commendation.

We pass now from the University proper to the influence which it extends throughout the country by means of its local examinations, both for boys and girls. They are intended chiefly 13 E. for the advantage of the middle-class schools, for whom there exists no organised system of inspection, such as the Privy Council provide for schools of a lower class; nor any recognised criterion of merit, such as the universities supply for schools of a higher class. They enable schoolmasters to send in for examination either whole classes or chosen representatives, and, by attracting to various centres the youth from all parts of England, they provide a largeness of competition which makes them a valuable test of excellence, and a powerful stimulus to increased exertion.

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The syndicate appointed for the purpose undertake to conduct an examination at any place where a local committee, formed for the purpose, will guarantee at least twenty-five candidates. If girls are to be examined as well as boys, it is necessary that 39 19 E. there should be a committee of ladies, one of whom will undertake the office of local secretary.

This committee will have to see to the proper accommodation of all students not resident in the place of examination; to pro23 E. vide a suitable room for the examination, separate from that in which the boys are examined; and to send a responsible representative to be present during the time of examination.

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The University fee, whether for boys or girls, is £1 per 5 47W. candidate, and the local committee have the power to charge an additional fee to cover their own expenses. After each examination, the students who pass with credit, or satisfy the examiners, are entitled to receive certificates to that effect, which also specify the subjects in which the student has been examined. The names are also published in three alphabetical honer classes, and a list appended of those who merely pass. In determining the classes, account is taken of every part of the examination, provided that in that part the student has obtained more than a certain fixed minimum of marks. Regard is had throughout to the handwriting and spelling.

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parents or guardians object.

2. English. This embraces a piece of original composition; a paper on a chosen portion of English history; and another on physical, political, and commercial geography, with especial reference to Great Britain and her dependencies.

3. Latin.-Papers on two chosen Latin books, involving geographical and historical allusions, grammar and parsing; also one passage from some Latin author, not announced beforehand, and a passage of English, with Latin words supplied for translation into Latin.

4. Greek.-Corresponding papers to those in Latin, omitting the composition.

5. French.

6. German.

In these the papers will correspond to those in Latin.

7. Pure Mathematics.-Euclid I.-VI.; algebra as far as proportion; plane trignometry to the solution of triangles, logarithms, and mensuration.

8. Elementary Mechanics, embracing the parallelogram of forces, the centre of gravity, and the mechanical powers. 9. Elementary Chemistry and the laws of chemical combination, substances being given for testing.

10. (a) Elementary Zoology, embracing the classification of animals and the uses of animal products.

(b) Botany. The classification of plants and their geographical distribution, specimens being given for description. No student will be examined in both (a) and (b). Amongst the above sections two, as we have said, are compulsory. These two must not be both 3 and 4, or both 5 and 6, or both 7 and 8, or both 9 and 10.

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1. Religious Knowledge.—Subjects as above, with the addition of the Book of Common Prayer, and Paley's "Hora Pauline;" also, in the New Testament subject, credit will be given for a knowledge of the original Greek.

2. English.-Subjects as above, with the addition of a play of Shakespeare, the outlines of political economy, and a short English composition.

3. Latin and Greek as above, including one piece of Latin composition.

4. French and German as above, with a piece of composition in both languages.

5. Pure and Applied Mathematics, embracing Euclid, algebra,

trigonometry, conic sections, elementary statics, mechanics, hydrostatics, and astronomy.

6. Chemistry, embracing general principles of chemical science, and the experimental laws of heat, magnetism, and electricity.

7. Zoology, Botany, or Geology, no student being examined in more than one of these subjects.

8. Drawing from the flat, from models, and in perspective. 9. Music, embracing the history and principles of the art. Of these nine sections, no one will be examined in more than five. Every one must take in 1, unless, as above, it be objected to; and every student must satisfy the examiners in three of the first seven, or in two of the first seven and one of the last two. A fair knowledge of one of the subjects comprised in each section will enable the student to pass in that section.

Papers relating to the examinations may be obtained at Messrs. Rivington's, the publishers, and any further information required will be given by the secretary of the Local Examina.

tion Syndicate at Cambridge.

It is scarcely necessary for us to point out the advantages offered by such examinations as these, so extensive in the subjects which they embrace, yet giving every prominence to select would be well for all who are interested in the training of the rising generation, to test the knowledge of those in their charge by requiring them to pass one of these examinations before considering their education complete.

reading. We close our account of them by suggesting that it

COMPARATIVE ANATOMY.-XVII.

PTEROPODA-CEPHALOPODA.

PTEROPODA.

PERHAPS there is no class of animals less likely to come under the notice of the reader than those which belong to this class. This is not because they are few in number, for they exist in such countless numbers in the ocean that, though they are all of small size, they discolour large tracts of its waters; clouding it just as the countless flakes of the snow-fall make the heavens look turbid. Ships may sail for many hours through these swarming myriads, and it is supposed that they form a large part of the diet of the huge whales which, rushing through the throng with open mouth, strain out the little creatures from the waters by the aid of the whalebone fringes of their jaws, and so manage to satisfy an appetite which must be as exacting as their bulk is large. The reason that we see so little of these multitudinous creatures is that they are strictly oceanic in their habits -that is, they live in mid-ocean, and seldom come near any shores. Moreover, they seem to be more or less nocturnal in their habits, retiring into the depths of the sea during the heat of mid-day, and coming to the surface in the evening. They have, however, been seen, even during the day, sporting about in the neighbour. hood of those great masses of ocean-weed called sargassum, which float in the middle of the Atlantic, occupying the centre of that vast revolving current, part of which is called the Gulf Stream.

The distinguishing character of these animals, from which they derive their name, is that they possess two wide expansions of the mantle, which are very muscular, stretching away on either side from the back of the neck. These flaps have been called wings, and the animals themselves butterflies of the sea; those who have observed their motions say that it is so brisk and constant that the simile is not an unnatural one.

There are two divisions of the Pteropoda, in one of which there is no shell, of which Clio Borealis, a little creature about half an inch long, may be taken as the type; while the other consists of animals which have shells, and of these Hyalea may be taken as a good example. In Hyalea the shell is a pretty object, reminding one of a watch-pocket such as is hung to a bed. It is all in one piece, but cut down the sides by such deep slits that it may be said to consist of two portions, one of which is flat, or nearly so, and the other is bulging. The animal rests in this little inflexible pocket, and can retract itself completely within the cavity; but ordinarily, when not alarmed, it thrusts its head and wings out of the top, and protrudes two folds of its thin mantle through the side slits, and bends them round the shell, both before and behind, so as to make their edges meet. The head is often not very distinct, and although some of these

creatures have very elaborate organs for seizing and holding prey, they are so minute as to require high powers of the microscope to detect them at all. The organs of sense are but ill-developed. Thus, though they certainly occupy a position between the Gasteropoda and Cephalopoda, they seem in some respects inferior to both. The mass of internal organs of the animal occupies a much smaller space than the interior of the shell. They are carnivorous, feeding on small animals. The mouth leads, in hyalea, into a narrow throat, and this into a round stomach. The short intestine opens into the cavity between the mantle walls. They are opistho branchiate-that is, their gills are situated behind the heart. The heart is, as in all molluscs, systemic, and receives blood from the gills, and propels it to the body. The liver is large, and there is below it an organ supposed to perform the functions of a kidney.

The nervous system consists of a central mass, composed of two ganglia, united by a band which passes under the throat, and this sends off nerves to the wings and mantle. In Clio Borealis there are four large ganglia and two small ones in the same position. This creature has a bi-lobed hood, which can cover all the head, while the tentacles run through it, and so warn the animal, by the sense of touch, of any external object; and then, if this object be prey of any kind, it throws back its hood and exposes six organs, placed three on each side of the mouth, which are studded over with an immense number of tubes, each of which can protrude from its end twenty organs which can act as suckers, and so their minute victims are secured and passed to the triangular mouth, which is furnished with small, singularlyshaped jaws. In Clio Borealis there are two round dark spots at the back of the hood to which nerves run, and these were once supposed to be eyes; but as little stones have been found in these organs, they are now supposed to be ears. The sexes are united in each individual.

CEPHALOPODA.

This last and highest class of the Mollusca differs from the rest in containing animals with far higher powers of locomotion and perception than any of the others. The different species are, it is true, often very uncouth and grotesque in appearance, but probably the grotesqueness is due to the fact that they seldom come under our notice. Every creature which we have never observed before, and which differs in external form from those with which we have been previously acquainted, always creates the impression of outlandishness, however well it may be adapted to its own conditions of life. If we were to account strange and grotesque those forms which differ most from the type upon which most creatures are formed, both man and the horse would be thought very strange creatures. When, however, we find organs whose uses we know well, and with whose outward form the eye is familiarised, blended with other organs which have never before come under our notice, no doubt the impression of uncouthness is strongest. Thus, the fact that a cuttle-fish has large eyes on each side of its head very much like our own, and also a beak like that of a parrot, united with a body like a leathern bag, from the mouth of which stretch long arms studded with sucking cups, makes this creature not only appear singular, but even disgusting to some.

In the higher examples of Articulata we find that as they become more organised and complicated in structure, and better suited to the accomplishment of the noble vital functions, so do they tend to differ from all other creatures in the other branches of the animal kingdom. We may, perhaps, assume that the branch Vertebrata contains the highest of all animals; but in proportion as insects become perfected, so far do they differ from vertebrates. Though the functions be the same, the methods by which they are performed differ utterly. The faculties of perception and locomotion are some of the highest animal powers, and these are possessed in quite as large measure by the dragon-fly as by man or the dog; but the instruments by which the former moves and sees are not only quite different from those employed by the latter, but they are the more different, as manifested throughout the class Insecta, as they become more perfect. On the other hand, as the Mollusca

become more highly organised they become more like the Vertebrata, and most of all like them in those organs which minister to the higher functions, for which the sub-kingdom is not noted. Thus, not only does the eye of the cuttle-fish much resemble that of a vertebrate, but, associated with the greater

powers of perception and locomotion, is the development of a large concentrated brain, enclosed in some cases in a carti laginous box, from which prolongations are extended to shield and support the sense-capsules (ears and eyes), and also to support the organs of motion. This cartilage seems to be the true representative or homologue of the internal skeleton of the vertebrates, and in this class it becomes developed from the merest rudiment until it entirely supplants the shell, which we find, not only in this class, but in the other classes of the Mollusca, playing the part, not merely of a protection, but also a fulcrum, or fixed hard part, from which muscles could move the soft parts of the body. However much we might wish it otherwise, we must, therefore, consider ourselves more nearly allied to the gross, dull, and sluggish Mollusca, than to the active and graceful articulates; but though the gap in the series which cuts off the vertebrates from the invertebrates is doubtless the most decided and definite which is found in the whole animal kingdom, yet the cephalopods furnish a link which connects us with the Mollusca, while there is no such link between the articulates and the branch to which we belong.

The Cephalopoda are so called because the integument of the body is drawn out round the mouth into long, tapering, flexible thongs, which are the instruments which have to serve, not only as feelers and arms, but also as legs. In this latter capacity they are used when the animal makes its way over solid ground, and, from their position, the animal must of course walk upon its head, and hence the name head-footed, or head walkers. This mode of progression is, however, seldom resorted to, as the creatures are oceanic rather than terrestrial, and made for swimming rather than walking. They only approach the shore to lay their eggs, but swim the sea in order to procure prey. Not unfrequently, however, they have a retreat in the dark cranny of some submarine rock, in the neighbourhood of which the refuse of their prey is seen to accumulate.

The cephalopods are divided into two great divisions, called, according to the number of their gills, Tetrabranchiata and Dibranchiata; or, according to the number of their arms, Tentaculifera and Acetabulifera. To the former belongs the pearly nautilus, whose shells are so commonly seen in naturalists' shops, but which belong to at most only two species of animals. All the rest of this once numerously represented sub-class are fossil. The ammonites of the secondary period all give indications that they belong to this division, and their variety of form and number-the number of individuals—which lived during that period is truly amazing. It is curious that, while all the ammonites have died out, the nautilus, which still exists, represents a genus which lived in the primary ages, long before the former came into existence. It is probable that no other genus, and certainly none so high in the animal scale, has had so prolonged an existence on our planet. Since the Nautilus pompilius and the Nautilus umbilicatus are the only two existing species, we are compelled to interpret the structure of all the soft organs possessed by this class by an examination of these species only, and even this examination is difficult to accomplish; for though the shells of these creatures are comparatively numerous, and are found washed up at the sea margin, the animals are oceanic and very wary, so that they can only be captured on rare occasions. In fact, we are dependent upon the investigations of two anatomists only, Mr. Owen and M. Valenciennes, for a description of the nautilus.

The pearly nautilus has a shell rolled up in a spire, whose whorls are all in one plane-that is, the outer circles are wound evenly round the inner ones, as a piece of flat tape is wound upon itself. This method of rendering the shell compact is very general throughout the class (though not absolutely universal, and serves to distinguish the shells of Cephalopoda from those of the Gasteropoda, which are never wound evenly round the central portion, but always to one side of the plane, in which the preceeding whorls lie just in the same manner as the string of a peg-top is wound around it. number of chambers, all of which communicate with each other by a little tubular opening, situated in the centre of each par tition. Though these chambers and the communicating tubes are lined with live membrane proceeding from the animal, all the essential parts of that animal are contained in its bag-like, short, cylindrical body, which is lodged in the last large chamber of the shell, whose orifice is wide. As the nautilus grows it secretes more shell from its mantle, thus extending the mouth

This shell is divided into a

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PTEROPODA :-I., I'. SHELLS OF HYALEA. II. ANIMAL IN ITS SHELL (DIACRIA). III. HYALEA COMPLANATA, DRAWN AS THOUGH IT WERE TRANSPARENT, TO SHOW THE VISCERA, ETC. CEPHALOPODA :-IV. LOLIGO, A DECAPOD ACETABULIFEROUS GENUS. V. OCTOPUS VULGARIS, THE POULPE OPENED TO SHOW THE ARRANGEMENT OF THE ORGANS. VI. SUCKER FROM THE ARM OF A SEPIA. VI'. THE SAME IN SECTION, TO SHOW THE PISTON AND THE MUSCLES WHICH RETRACT IT. VII. SIDE VIEW OF THE GANGLIONIC RING OR CENTRAL NERVOUS SYSTEM OF SEPIA. VIII. SIDE VIEW OF AN IMPERFECT AMMONITE, SHOWING THE NOTCHED SUTURE. IX. SIDE VIEW OF SAME. X. RESTORED BELEMNITE AND ITS SHELL.

Refs. to Nos. in Figs. III. 1, 1, fins or wings; 2, 2, mantle which lines and also overlaps the shell; 3, mouth; 4, stomach; 5, intestine; 6, liver; 7, ventricle of heart; 8, auricle of ditto; 9, ascending vessel which gives branches to the fins; 10, gills; 11, ganglion, giving nerves to fins and mantle. V. 1, 1, 1, 1, roots of the arms, which are cut short; 2, 2, mantle thrown back; 3, funnel, or locomotive pipe; 4, buccal mass; 5, crop; 6, stomach; 7, blind sack opening into the stomach; 8, intestine; 9, arms; 10, 10', auricles; 11, ventricle; 12, gill heart (there are two of these, but the left is concealed); 13, 13, vena cava-veins leading direct to the branchial hearts; 14, spongy masses round venæ cavæ, supposed to be kidneys; 15, ovary; 16, 16', oviduct; 17, ascending aorta, or main trunk. VII. 1, supra-oesophageal ganglion; 2, sub-cesophageal ganglion (anterior); 3, ditto (posterior); 4, 5, upper and under mouth ganglia; 6, nerves in arms; 7, ditto to mantle; 8, ditto to eye; 9, buccal mass; 10, throat.

from the outside. The head of the nautilus is but little distinct from the body, and from its upper side the mantle is developed into two folds. One of these adheres to the shell, and the other is puckered into a kind of hood, which falls as a kind of door to close the opening of the shell when the animal retires within it. This thickened part is also used to crawl upon. The funnel,

a shelly structure, and this is surrounded by a multitude of feelers, all of which can be retracted into sheaths. These animals have four gills instead of two, and they have no inkbag; otherwise, their internal structure is not unlike the other class.

The Dibranchiate cephalopods are of higher organism then

the nautilus. They have been called Acetabulifera, because of certain curious appendages to their arms. Their arms are not short, numerous, and retractile within sheaths, as those of the nautilus are, but of definite number (eight or ten), long, and on their inner sides-that is, towards the mouth-they are studded with a single or double row of acetabula. The word acetabulum is the ancient name given to a vinegar-cruet, and was first applied anatomically to the hollow in the pelvis into which the head of the thigh-bone of man is received. Since then it has always been applied to any cup-like organ which has a deeper depression in the centre of the cup. These cups are sometimes stalked, and sometimes set directly to the arms. The cup is of a cartilaginous consistence, while in the pit there is a leathery piston, which can be retracted by proper muscles after the round edge of the cup has been applied to any object. When the piston is retracted it of course creates a vacuum in the cup, and as there are many hundreds of these cups on the arms of the animal, it can lay a very firm hold on its prey, and drag it with great force towards its beak-like mouth. Besides tho cup-like discs, or suckers, the arms of some of the cephalopods are furnished with horny hooks, which assist in retaining the prey. Unlike the nautilus, the jaws of the ctopus are horny and sharp, like the bill of a parrot, only the lower jaw protrudes beyond the upper one.

The shell of these creatures is far less developed than in the other division of this class. For the most part, it is not apparent at all on the outside, but lies loose in the muscular skin of the back, which it supports, and thus provides that the animal can be thrust along by the working of the siphon or by the fins. In the paper nautilus, however (Argonauta argo), there is a beautiful external shell, which is not divided into chambers. This shell, though it lodges the bag-like body, has no sort of likeness in form to the shape of the body. Thus, when it was naturally supposed that the shell was secreted, as in the case of the other Mollusca, by the mantle, or investment of the body, naturalists could not imagine how so beautiful a structure was moulded on so uncouth a form. It has since been ascertained that the shell is formed by two of the arms, which have a large membranous expansion fitted to secrete such a shell. Before the office of these arms was known, they gave rise in their turn to false conjectures, for it was then thought that this creature sat in its shell as in a boat, and, lifting the webbed arms above the surface of the ocean, was driven along as a ship by its sails. In the other octopods there is no representative of a shell, either external or internal. In some of the decapods it is horny, and in the shape of a pen. In others it is calcareous and thick, but nevertheless it is very light, being quite porous, and made up of very thin plates supported by little pillars. This is the case in the pounce-bone of the sepia. In others, again, as in spirula, the shell, though internal, is chambered, and is supposed, as in the case of the chambered shell of the nautilus, to contain air, which lightens the body and can be compressed when the animal wishes to sink. A number of curious fossils, called belemnites, on account of their resemblance to the head of a dart, have been identified as the prolongations of these internal chambered shells, and as these have been sometimes found associated with the hooks and ink-bag found in the cuttle-fish, there can be little doubt about the identification being genuine. The relation of the shell to the extinct animal is shown in the engraving. The funnel or siphon of the Dibranchiata is entire, and not split along its under side. It leads into a gill-chamber, into which also the ova and fæces are discharged. The buccal mass is globular and large. The tongue bears teeth directed backward, but is in part naked, and seems like an organ of taste. The narrow throat leads into a globular stomach or crop. Into the stomach a large blind sack enters, and the intestine is short, as is usually the case with carnivorous animals, as these are. The circulatory system is peculiar in being almost a closed circuit, and in having, not only a heart distributing the blood to the system, after being aërated at the gills, but also in having two distinct hearts driving the blood to the gills. The blood is conveyed to these branchial hearts through two large venous canals, whose walls have a spongy texture. These large veins are supposed to excrete from the blood, by means of the spongy walls, the ammoniacal liquid equivalent to the urine, and since the vessels lie in the water introduced through the funnel and gillchambers, of course this could become a means of getting rid of matters no longer useful from the nutritive stream. The ink-bag

is a peculiar organ situated in the recesses of the body, the duct from which is conveyed up and opens behind the funnel. The secretion is under the control of the animal, and when formed it thickens and obscures the water by a copious discharge. It is said that the Chinese made ink from this secretion, and it is still used as a pigment.

The whole of the Cephalopoda, both recent and extinct, may be classified thus:

TETRABRANCHIATA.-Eyes stalked, jaws shelly, and body attached to the shell by a muscle; gills, four.

Family 1.-Ammonitide: Shell of many chambers; that containing the body elongated, the aperture guarded by processes, and closed by an operculum; sutures angulated, and siphuncle external (or dorsal).

Family 2.-Orthoceratida: Shell with a small narrow aperture; siphuncle complicated.

Family 3.-Nautilido: Sutures simple; siphuncle contral. DIBRANCHIATA.-Eyes sessile; jaws horny; two gills; an

ink-bag.

Tribe I.-OCTOPODA: Eight arms; eyes fixed.

Family 1.-Argonautida: Dorsal arms webbed; female with a shell.

Family 2.-Octopodidae: Arms webbed between the roots. Tribe II.-DECAPODA: Eyes movable; body finned.

Family 3.-Teuthida: Fins nearly at the end of body. Family 4.-Belemnitido: Shell represented by a pen, terminating in a chambered cone; siphuncle on the ventral side.

Family 5.-Sepiada: Calcareous gladius; elongated tentacles.

Family 6.-Spirulida: Discordal, pearly, many-chambered shell, with ventral siphuncle.

LESSONS IN CHEMISTRY.-XXVI.

GOLD-PLATINUM. GOLD.

SYMBOL, Au-COMBINING WEIGHT, 196'5-SPECIFIO GRAVITY, 19-3. THIS, the most valued of the metals, is always found in a native state, frequently alloyed with small quantities of silver, copper, and some of the rarer metals. Generally its matrix is quartz rock, but by aqueous action this rock becomes degraded into sand, and the gold is carried down to the river-bed. From this source it was chiefly obtained before the discovery of the Californian and Australian gold-fields. It is separated from the sand by "washing"-that is, the sand, largely mixed with water, is allowed to run from one "cradle" to another, the light sand being thus washed away, and the heavy particles of gold remaining. In California and Australia the metal is found in lumps-"nuggets"-which have every appearance of having been fused; or it is extricated from the quartz. The rock is crushed, and the gold separated by "washing." The process of amalgamation has also been resorted to. The crushed quartz is mixed with mercury, which takes up the gold. The metals are afterwards separated by distilling off the mercury.

Gold is one of the heaviest of the metals, being only inferior to iridium and platinum. It is very malleable, being capable of being beaten out so thin as to allow green light to pass through it.

It is very soft. Bracelets of pure gold can be twisted round the arm. It melts at 1100 Cent.

No simple acid, except selenic, will dissolve it; but it is acted on by any mixture which liberates chlorine. Such a mixture is " aqua regia," which is composed of 1 of nitric and 4 of hydrochloric acid. The result of this action is auric tri-chloride (AuCl).

From this salt pure gold may be obtained by precipitating the metal from its solution by ferrous sulphate, according to this equation:

3FeSO, + AuCI; = FeCl, + Fe,3SO, + Au. The gold falls as a brown powder, which is purple to trans mitted light. Oxalic acid and the chloride of antimony have a like effect to ferrous sulphate.

Gilding is effected by causing gold-leaf to adhere to the sur

By siphuncle is meant the tube connecting the chambers of the shell.

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