the only condition essential to its fluidity: it is necessary that a certain quantity should be accumulated within it at the same instant of time.

To this property of matter we are indebted for the durability and usefulness of our metallic culinary vessels. Whilst they contain water there is no danger of their being melted; but when this precaution is neglected, and copper or tin vessels are exposed to the action of the fire, the solder by which their joints are united speedily melts, and the vessels become leaky, and perhaps fall to pieces.

The freezing-point of liquids, and the meltingpoint of solids, is materially affected by the admixture of two or more bodies of different kinds. Thus water, which usually becomes ice at 32°, may, by the addition of one part of common salt to three parts of water, be cooled down to 4° before it will show any symptoms of congelation. By a particular process it is possible to reduce the temperature of water, of solutions of crystallizable salts, and even of metals, below their ordmary points of congelation, and without producing that result. It appears, that whilst motion among the particles of bodies is one preparatory condition to a change of form, something more than motion is, under particular circumstances, required. We will endeavour to illustrate this by an example.

Having provided a glass vessel, with a long narrow neck, as denoted in the annexed figure, say, for instance, a Florence oil-flask, we should nearly fill it with boiling water, in which has been previously dissolved as great a quantity as possible of sulphate of soda (Glauber salts), and then tie securely over the mouth of the flask, two or three folds of moistened bladder, so as effectually to exclude the air. The height at which the liquid stands in the neck of the vessel should be denoted by a mark upon the glass, or it may be done more easily, by tying round it a piece of thread. Matters being thus arranged, the liquid should be permitted to cool down to the temperature of the surrounding air. When that is accomplished, it will be seen that the surface of the liquid has descended in the neck of the flask, denoting a diminution of its bulk. If we now ascertain as accurately as possible, by the hand, the comparative temperature of the flask, at the same time suddenly piercing the bladder, so as to admit the external air, it is probable that crystallization will instantly commence at the surface of the liquid, proceeding rapidly downwards, until the whole has become solid. By keeping the hand upon the flask, we shall perceive a very considerable increase of temperature; and by noting the mark upon its neck, we shall also find there has been an augmentation of bulk. Should it happen that crystallization does not commence on the admission of air, the object may generally be attained by slightly agitating the liquid. If that process be ineffectual, which is not very probable, a small stone, a piece of metal, or a single grain of any kind of salt, dropped into the flask, will immediately produce the desired result. To render this experiment the more interesting, we recommend the employment of two glass vessels, both of which should be filled with the solution; but whilst one is subjected to the treatment just described, the other should be left open to the influence of the atmosphere.

Flasks, as indicated by the figure, are the most convenient vessels for containing hot liquids in In chemical language, a saturated solution: that is, the boiling water is filled with the salt; it will dissolve no more of it.

chemical experiments, because they are not so liable to be fractured, as more irregularly-formed vessels ; but they are not absolutely necessary. When this, or any other particular form of apparatus, cannot be easily obtained, common phial-bottles may, with proper care, be made to supply their place.

Pure water, by a process somewhat similar to that we have explained, may be made to preserve its fluidity at a temperature equal to 27° below its ordinary freezing-point (32°.) It is deserving of remark, however, of water under these circumstances, that the instant it begins to freeze, its temperature rises from 5° to 32°, where it remains fixed, until the whole of the water has become solid. The ordinary melting-point of tin, is 442° but it may, notwithstanding, be cooled, by skilful management, to 438°, without solidifying. When it begins to assume the solid form, its temperature rises to 442°. Hence we learn, that the loss of sensible heat is not the sole cause of fluid bodies becoming solid; and that its addition is not all that is necessary to render a solid body fluid.

It may never fall within the compass of human knowledge, to understand, and to explain, all the conditions that are essential to the successive interchanges of which matter is susceptible; but we think it will not be denied, that heat is the primary and the most efficient agent in determining the greater part of the phenomena with which, at present, we are acquainted. Further, it may be remarked, that, in some of the instances referred to in the present paper, it is manifest that heat, which in one case evades our most diligent search by becoming latent, that is, concealed in any particular body, may, by a slight modification of circumstances, be drawn, so to speak, from its hiding-place, and rendered scnsible or free.

Solid bodies have their melting-points altered by being mixed with others of a different kind, whether solid or fluid. Mercury is frequently adulterated by lead, tin, and other cheap metals. Now, as mercury is a fluid metal at ordinary temperatures, we have here an instance of another metal (lead) whose melting-point, when unalloyed, is 606°, becoming permanently fluid by being combined with mercury in certain proportions. Two parts, of lead and one part of tin, when combined, will melt at 385°, which is 57° below the melting point of tin, and 221° below that of lead, when each of these metals are in a state of purity. This mixture constitutes the solder used by plumbers. An alloy of three parts lead, two of tin, and five of bismuth, melts at 197°, which is 15° below the temperature of boiling water. Spoons are made of these combined metals, which melt on being placed in tea, or any other liquid, at the temperature already mentioned. R. R.

Y MAEN CHWYF, OR ROCKING STONE, IN THE VALE OF TAFF, GLAMORGANSHIRE.

THE stone here represented, known in Welsh as, Y Maen Chwyf, (the Rocking Stone,) is situated on the western brink of a hill, called Coed-pen-maen, in the parish of Eglwysilan, Glamorganshire, above the turnpike-road from Merthyr to Cardiff, and nearly equidistant from both towns. From this spot may be seen the celebrated one-arched bridge over the Taff, near Newbridge, and fine views of several ramifications of the neighbouring hills and valleys. The romantic vale of Rhondda extends to the west, and a little nearer we have the salmon-leap, and fall of the Taff under Craig-yr-hesg; to the north-west, the equally beautiful vale of Cynon meets the eye,

THE PALACE OF JUSTICE AT ROUEN. It would be difficult to find in the whole of Europe, a district more rich in specimens of early splendid modern architecture, than that part of France which was formerly comprehended under the name of the province of Normandy; at all events, when we call to mind the connexion that formerly subsisted between the ancient duchy of that title and our own country, we are quite sure that it would be impossible to find out of England one which should be equally remarkable in that respect, and at the same time equally interesting to Englishmen in general. The city of Rouen contributes its full share of the attraction which has earned this distinction for the land in which it lies; its ecclesiastical buildings are among the finest in existence. Few cities in the world possess two such specimens of Gothic architecture as the Cathedral of Notre Dame, and the Abbey Church of St. Ouen *;-indeed, the latter is often called the finest Gothic edifice in France. Nor are the secular buildings of this city less worthy of mention; they include some of the most beautiful examples of the adaptation of the Gothic style to civil purposes that are to be found anywhere. At the head of these stands the Palais de Justice, or Palace of Justice, which is represented in the engraving contained in the preceding page; it is a highly interesting specimen of the sumptuous taste of the age in which it was erected, and forms, indeed, as one of our countrymen expresses it, the "civil" lion of the place.

It is not, however, on account of its intrinsic beauty alone, that the Palace of Justice is remarkable; the importance of the purposes to which it has been at various times applied, imparts to it a considerable degree of interest. At present, it is occupied as a court of justice, and serves as the place of election for the deputies who are returned from hence to the French House of Commons; under the old order of things, it constituted a hall of meeting for the provincial states of the duchy of Normandy, one of those miniature parliaments which existed in France previous to the Revolution; while, to mount a step higher in the scale of antiquity, before it was employed by the parliament, it used to be appropriated to the sittings of the ancient Court of Exchequer. From its origin, indeed, it was devoted to judicial purposes, or in French phrase, was "destined to be the sanctuary of the laws, and of justice." The circumstances under which it was founded are these. Until the close of the fifteenth century, there did not exist in Normandy any stationary court of judicature, the execution of the laws being intrusted to an ambulatory tribunal, called the Exchequer, which was established by Rollo, the first duke. This court, like the ancient parliaments of the kings of France, ordinarily held its sittings twice a year-in spring and in autumn; the place of its meeting depended on the pleasure of the sovereign, and was usually determined as in the case of the English Aula Regia, by his presence. This mode of administering justice was necessarily attended with great inconveniences, and accordingly in the year 1499, a petition was addressed by the provincial estates to the king of France, praying him to establish in the chief city of the province, a judicial tribunal, which should be fixed and permanent, like those already established in other cities of the kingdom. Louis the Twelfth, so celebrated as the good king, then occupied the throne, and the French writers say that it would have been impossible for a monarch who had shown ⚫ so much regard for the happiness of his people, to To be described in future papers.

réfuse granting a privilege so obviously conducive to their good. The king did not refuse; by an edict of the same year as the application, the court of Exchequer of Normandy was declared to be "fixed for ever in the good city of Rouen," and was directed "to hold its sittings in the great hall of the castle, till such time as another suitable place should be made ready." It was to provide such a place that the Palace of Justice was erected; a very few years, however, elapsed, before the court ceased to hold its sittings in the building so especially founded for it.

"The name of Exchequer," says Mr. Dawson Turner, "was perhaps unpleasing to the crown, as it reminded the Normans of the ancient independence of their duchy; and in 1515, Francis the First ordered that the court should thenceforward be known as the Parliament of Normandy, thus assimilating it in its appellation to the other supreme tribunals of the kingdom."

The palace, in its present form, presents three distinct buildings, forming three sides of a quadrangle. The oldest of these is the one which appears in the front of our engraving; it bears the name of the Salle des Procureurs (or Hall of the Attornies,) and was erected six years before the structure to its right, which is more strictly the Palace of Justice. Its original destination was that of a Bourse, or Exchange, and the chief object in raising it was, according to the edict issued by the bailiff on the occasion, to put a stop to the impiety of those who were in the habit of assembling in the cathedral, even on festival days, for the purpose of transacting business. The exterior of this building is simple; the richest part is the gable, which has on either side an octangular turret decorated with what architects call "crocketed pinnacles" and flying buttresses.

The interior consists of a noble hall, which is raised above a basement, originally intended as a place for shops, but now forming a part of the prison. The length of the room is upwards of 160 feet, and its breadth more than fifty; the appearance which it presents is grand and imposing. The roof is of timber; it is a plain arch, extremely bold, and destitute, as Mr. Turner remarks, of the open tie-beams and arches, or the knot-work and cross-timber that usually adorn the old English roofs. The wood employed is oak; and the dark colour which it has acquired by age, contributes much to the solemn appearance of this vaulted apartment. The only ornaments to be found within it, are a series of niches running round the walls; the workmanship of these is delicate, but they are all unoccupied.

Peter Heylin, an English divine, who visited France in the earlier part of the seventeenth century, describes the building thus: "In the great hall into which you ascend by some thirty steppes or upwards, are the seats and desks of the procurators; every one's name written in capital letters over his head. These procurators are like our attornies to prepare causes, and to make them ready for the advocates. In this hall do suitors use either to attend on, or to walke up and down, or to confer with their pleaders.”

The building, of which a portion is seen in our view, to the right of the Hall of the Attornies, is, strictly speaking, the Hall of Justice; it is far more sumptuous than the other, both internally and externally. It was erected exclusively for the sittings of the Exchequer, under the circumstances we have already mentioned; and is spoken of by the French writers as a magnificent edifice. The front extends in width more than two hundred feet, and "is decorated," say Jolimont, "with every thing that is most delicate and most rich in the architecture of its age."