These pieces have a shining silvery aspect; they are dispersed, at first irregularly, in small numbers, but increase, both in size and numbers, till the whole bottom is covered, and if the frost continues severe, grow in height, but in a very irregular manner, so as to obliterate the earlier somewhat symmetrical shapes, till the streams are raised high above their former levels, and frequently made to overflow their banks.

The name applied to the ground-ice to which the above description refers, is a better one even than that . of the Germans. In a district where it occurs almost every winter, and often repeatedly during that season, and where many of the rivers are crossed by means of fords, its existence influences too much their economical arrangements not to excite their particular attention, especially as many horses refuse to enter any stream even slightly impeded by it, being greatly alarmed by the pieces which break and float up from the bottom by the action of their feet. A substance with which all are so well acquainted, is known by an appropriate name. It is called ground-gru; gru being the term applied to snow saturated with, or swimming in, water. The formation of ground-gru occurs only when the temperature of the whole mass of water is reduced to, or nearly to, 32°, the temperature of the air being several degrees below that point. It is preceded by a continuance for some time of a clear state of the sky. But while forming under the continuance of a cloudless sky, its increase is impeded during the day, but when a densely clouded state of the sky occurs, and continues for twenty-four hours, the gru becomes detached from the bottom, and floats down the stream. Should the temperature of the air continue low, with a clouded sky, or get lower, the ground-gru is not renewed, but the river is speedily frozen over at the surface. In fact, it frequently occurs in frosty winters, that the rivers, filled and so impeded by ground-gru, as to be raised above their banks, are found returned into their natural channels, and there frozen over at the surface, but flowing over a clear bottom, in a space of time so short as to appear very wonderful to those who have not investigated the cause. The process is named, by the country people, the flitting of the ice.

Some interesting observations on the same subject were made by the Rev. Mr. Eisdale, and read by him before the Philosophical Society of Perth, in December, 1831, being subsequently communicated to JAMESON'S New Edinburgh Philosophical Journal. From thence we gain the following particulars. Ground-ice, as observed by Mr. Eisdale, is produced only in the most rapid and rugged streams: it commences at the bottom of the water, and extends upwards to the surface. He speaks of that kind of ice as being well known in all northern climates from its annoying effects in obstructing all works which are carried on by the impelling power of water. When ice collects on the surface of mill-streams, it is easily managed and broken up, but when ground-ice forms, the case is perfectly hopeless, the streams being obstructed and gorged up from the very bottom. This kind of ice is called in the south of Scotland" lappered ice," an epithet which the common people apply to the natural coagulation of milk.

The first appearance of this ice at Perth occurs on the setting-in of a severe frost, before the true ice has made much progress in advancing from the sides to the centre of the river: nearly the whole body of the stream above the bridge is then occupied by large irregular masses of floating ice of very considerable thickness, far beyond anything that could be effected by the natural operation of the frost in surface freezings. These masses are formed in the most rugged currents, adhering to the projecting rocks, and rough inequalities at the bottom, and increasing upwards, till their bulk and smaller specific gravity as compared with water, enable the stream to tear them from their fastenings.

and hurry them down the river; until being stopped by the flow of the tide, they became closely compacted to, gether, and agglutinated by the frost, by which means great obstacles are presented to navigation. A curious example of the formation of the ground-ice was reja ed to Mr. Eisdale by a miller in the western part of Scotland. During a severe frost, when the mill-lead was entirely free from any kind of ice, the miller had occasion one day to lop some branches from a tree which overhung the lead; one of them fell into the water, and was left there, as he did not apprehend any ill consequences from so trifling an occurrence. Next day, however, to his astonishment, the water was turned entirely out of the lead, and had overflowed a large portion of an adjoining meadow. On proceeding to ascertain the cause, he found that a solid barrier of ice had been formed across the lead, where the branch had fallen in, so as completely to prevent any water from passing, whilst the rest of the lead was free from ice.

Mr. Knight, the celebrated botanist, has related an observation which is the more valuable, as it seems in some respects to afford a clue to the secret of the formation of ice in the bottom of rivers; he says:I first witnessed the existence of ice in the bottom of the water in the river Teme, which passes near my residence in Herefordshire. In a morning which succeeded the river appeared to be covered over with frozen matter, an intensely cold night, the stones in the rocky bed of which reflected a kind of silvery whiteness, and which upon examination, I found to consist of numerous frozen spicula, crossing each other in every direction, as in snow, but not having anywhere, except very near the shore, assumed the state of firm compact ice. The river was not at this time frozen over in any part; but the temperature pieces of ice had everywhere formed upon it in its more of the water was obviously at the freezing-point, for small stagnant parts near the shores; and upon a mill-pond, just above the shallow stream (in the bottom of which I had observed the ice), I noticed millions of little frozen spicula floating upon the water. At the end of this mill-pond the water fell over a low weir, and entered a narrow channel, where its course was obstructed by points of rock and large occasioned, which apparently drew the floating spicula stones. By these, numerous eddies and gyrations were under water; and I found the frozen matter to accumulate much more abundantly upon such parts of these stones as stood opposed to the current, where that was not very rapid, below the little falls or very rapid parts of the river. I have reason to believe that it would have accumulated in very large quantities if the weather had continued sufficiently cold; for I had previously heard from persons of respectable character, who had no interest, nor, I believe, intention to deceive me, that during a long and severe frost some years ago, before I became an inhabitant of my present house, the whole bed of the river in the part abovementioned had been covered over with a thick coat of ice. But it was not till the month of February that I witnessed the apparent deposition of ice in the manner which I have described; and as the day afterwards became bright, the spicula soon ceased to form, and the ice to accumulate; and before the middle of the day the greater part of it had disappeared.

Upon some large stones near the shore, of which parts were out of the water, and upon pieces of native rock, under similar circumstances, the ice beneath the water had acquired a firmer texture, but appeared from its whiteness to have been first formed of congregated spicula, and to have subsequently frozen into a firm mass, owing to the lower temperature of the stone or rock. Ice of this kind extended in a few places, eighteen inches from the shore, of the water, and did not dissolve near so rapidly as and lay three or four inches from the level of the surface that which was deposited upon stones more distant from the shores.

The fact, of which the above instances give abundant evidence, had been noticed by fishermen and others, long before it became the subject of discussion with scientific men.

In the year 1730, when the atmosphere was at the temperature of nearly 16° Fahr., a person named Hales saw at Teddington, the surface of the Thames, near the

banks, covered with a layer of ice one third of an inch in thickness. There was also at the same time, a second layer below, of greater thickness, which followed the depth of the river, as it adhered to the bottom. This sheet was united to the upper one, even on the water-side; but it was gradually separated in proportion, as, in proceeding into the river, the depth of the water increased. It was not solid as the first, and was mixed with sand, and even stones, which the flakes sometimes carried with them in their movement upwards.

A few more instances of the occurrence of groundice in rivers, and the mode in which the circumstance is explained by scientific men, will be given on another

occasion.

The spirit of domestic peace,

Though calm and gentle as the brooding dove
And ever murmuring forth a quiet song,
Guards powerful as the sword of Cherubim,
The hallowed porch. She hath an heavenly smile,
That sinks into the sullen soul of vice,
And wins him o'er to virtue.-WILSON.

WHERE there are no roads there are always many ways.

AMONG the fathers of the Arabian philosophy may be numbered Honain, an eminent Christian physician, who translated the Elements of Euclid, and other Greek authors, into Arabic. He flourished in the ninth century, under the caliph Al-Mamon, who was not only an illustrious patron of learning, but was himself no mean adept in several branches of science.

One day, after some medical conversation, the caliph said to Honain, "Teach me a prescription by which I may take off any enemy I please, without being discovered." Honain declining to give an answer, and pleading ignorance, was imprisoned. Being brought again, after a year's interval, into the caliph's presence, and still persisting in ignorance, though threatened with death, the caliph smiled upon him, and said, "Be of good cheer, we were only trying thee, that we might have the greater confidence in thee." As Honain upon this bowed down and kissed the earth, "What hindered thee," said the caliph, "from granting our request, when thou sawest us appear so ready to perform what we threatened?" "Two things," replied Honain; "my religion and my profession. My religion, which commands me to do good to my enemies; and my profession, which was purely instituted for the benefit of mankind." "Two noble laws!" said the caliph; and immediately presented him, according to the eastern usage, with rich garments, and a sum of money.

As many natural bodies, whilst they are still entire, are corrupted and putrefy, so the solid knowledge of things often degenerates into subtile, vain, and silly speculations, which, although they may not seem altogether destitute of ingenuity, are insipid and useless. This kind of unsound learning, which preys upon itself, has often appeared among men who have much leisure, quick parts, and little reading; and being, moreover, in a great measure, ignorant of the history both of nature and of the world; out of very flimsy materials, but with the most rapid and violent motion of the shuttle of thought, they have woven those laborious webs which are preserved in their writings. The truth is, that the human mind, when it is employed upon external objects, is directed in its operations by the nature of the materials upon which its faculties are exercised: but if, like the spider, it draws its materials from within itself, it produces cobwebs of learning, wonderful indeed for the fineness of the threads, and the delicacy of the workmanship, but of no real value or use.-LORD BACON.

CHESS.

In our recent notice of the solution of M. Calvi's problem, it was stated that when a pawn arrived at its eighth square it is sometimes necessary to exchange it for some other piece than a Queen; but that, as the

* See Saturday Magazine, Vol XXIII., pp. 192 and 256

Queen has the powers of all the other pieces except the Knight, it is not necessary to choose a Bishop or a Rook; but that it may be desirable to choose a Knight on account of his peculiar checking power. We have been reminded by a correspondent, Mr. E. J. Catlow, that it may happen that the player advancing his pawn to the eighth square and claiming a Queen, would stale-mate his adversary; while by claiming a Bishop in one case, and a Rook in another, he may win the game. Our correspondent has invented two such positions, which are given below. It will be seen from the solutions that in either case it is possible to have too much mating power; for the Queen, combining the moves of the Bishop and the Rook, leaves no move to the adverse King, and consequently he is stale-mated.

I. White to move, and to check-mate in two moves.

This manufacture originated at the time of the commencement of the final struggle between Prussia and Napoleon. The country, impoverished by long and unsuccessful wars, was enabled to cope with her oppressor chiefly by the patriotism of her sons who yielded their active services, and of her daughters who, with a noble generosity, sent their jewels and trinkets to the royal treasury. Those who made this sacrifice received in return rings, crosses, and other ornaments, in cast-iron, which bore the inscription, Ich gab Guld um Eisen: "I gave gold for iron:" and to the present day these articles are much valued by the possessors and their families.

Strangers are freely admitted to the Iron Foundry to see the casting, which usually takes place in the evening. The castings are not, however, confined to trinkets; busts, statues, bas-reliefs, copies of pictures, monumental slabs, &c., are cast with equal success; for whether the object cast be a colossal statue, or the minute filagree ornaments of a lady's toilet, the casting cannot be equalled in delicacy and fineness of impression in any other part of Europe. It is said that this excellence is due to the quality of the Silesian iron; others attribute it to the care bestowed on the moulds, which are formed of a very fine sand mixed with a small portion of clay.

Dr. Friedenberg, in his translation into German of Mr. Babbage's work on the Economy of Manufactures, mentions the Berlin cast-iron ornaments as an interesting example of the increased value of manufactured articles in comparison with the raw material.

In one of the principal manufactures of these ornaments, such is the fineness and delicacy of those separate arabesques, rosettes, medallions, &c., of which the larger ornaments are composed, that it requires nearly ten thousand of them to make up a pound weight. The price increases in proportion to the fineness, as will be seen by the following table, which gives the prices of one eminent Berlin manufacturer.

Taking the price of the grey iron, from which these ornaments are made, at 6s. per cwt., on an average, the value of the material is increased 1100 times in the coarser articles, and 9827 times in the finest.

The above are the retail prices, and wholesale prices are probably one-sixth or one-eighth less. But compared with old prices the present ones are much reduced. About the year 1827 they were twice as high, and about the year 1820 three times, so that at that time Berlin cast iron was nearly of equal value with gold,—a remarkable example, and, perhaps, one of the strongest proofs of the influence of the industry of manufacturers on the wealth of the state, especially when we consider that the cast-iron ornaments are

made of native material, and exported in large quantities abroad, and even, indeed, to America. This branch of native industry, however, has been greatly injured by the extensive imitation of the articles, and the sale of them at a cheaper rate. The facility of imitation of the most saleable objects, by purchasing them at a low price, using them as models, and then casting articles of the same description, enables the imitator to offer his goods at such a low price that the original manufacturer, who has been at the expense of much time and capital in the designing and forming a brass model, finds it impossible to enter into competition with him. So that the manufacturer not venturing to expend much capital on new models, which do not repay the outlay, the articles by repeated castings lose much of their sharpness and beauty, and the natural consequence is that their reputation abroad is injured, and, notwithstanding the moderate prices, the sale must decline. On this account some of the first manufacturers have given up the business, and the task of improving and perfecting this branch of industry now rests in the hands of a few.

Dr. Friedenberg's account of the deterioration of this interesting branch of manufacture is verified by expe rience. We have recently inspected some cast-iron ornamental articles from Berlin, and found them entirely deficient in that sharpness of outline and precision of form for which they were once celebrated.

EFFECTS OF A SOLAR ECLIPSE ON ANIMALS.

In his report on the eclipse of July 8th, 1842, M. Arago always disbelieved, that a friend of his put five healthy and mentions, in support of a popular notion which he had lively linnets in a cage together, and fed them immediately before the eclipse. At the end of it three of them were found dead. Other indications of the alarm it produced were seen in a dog which had long been kept fasting, and which was eating hungrily when the eclipse commenced, but left his food as soon as the darkness set in. A colony from their labours at the same moment. of ants which had been working actively, suddenly ceased

ON THE DURABILITY OF STONE
BUILDINGS.
I.

ON THE CHOICE OF A STONE FOR BUILDING
PURPOSES.

EVERYTHING belonging to the earth, whether in its primitive state, or modified by human hands, is submitted to certain and innumerable laws of destruction, as permanent and universal as those which produce the planetary motions. The operations of nature, when slow, are no less sure; however man may for a time usurp dominion over her she is certain of recovering her empire. He converts her rocks, her stones, her trees, into forms of palaces, houses, and ships; he employs the metals found in the bosom of the earth as instruments of power, and the sands and clays which constitute its surface as ornaments and resources of luxury; he imprisons air by water, and tortures water by fire to change, to modify, or destroy the natural forms of things. But in some lustrums his works begin to change, and in a few centuries they decay and are in ruins; and his mighty temples, framed, as it were, for divine purposes, and his bridges formed of granite, and ribbed with iron, and his walls for defence, and the splendid monuments by which he has endeavoured to give eternity even to its structures which have resisted the waves of the ocean, the perishable remains, are gradually destroyed; and these tempest of the sky, and the stroke of the lightning, shall yield to the operation of the dews of heaven, of frost, rain, vapour, and imperceptible atmospheric influences; and as the worm devours the lineaments of his mortal beauty, so the lichens and the moss, and the most insignificant plants, humble and insignificant insects shall undermine and sap shall feed upon his columns and his pyramids, and the most the foundations of his colossal works, and make their habitations amongst the ruins of his palaces, and the falling seats of his earthly glory.-SIR HUMPHREY DAVY.

Although it is true that all human works must decay, yet it is a point of great importance to ourselves and our successors whether that decay be slow or speedy. The causes enumerated in the above eloquent passage, though sure, are exceedingly slow in their action, and provided the building materials have been selected with reference as well to their durability as to their beauty, the resulting structure may defy the corroding tooth of time for many ages, and we may thus transmit to a long posterity, lasting memorials of our wisdom and science, as well as of our piety. Modern science has to a very great extent enabled the architect and builder to determine beforehand what is the durability of any given stone, and it is with great pleasure that we now notice the extensive inquiry made at the suggestion of Mr. Barry, the architect of the new Houses of Parliament, under the Commission issued by Her Majesty's Government, to investigate the qualities of stone in various parts of the kingdom, in order to select that which should best ensure perpetuity to this grand national monument. This commission, consisting of Mr. Barry, Sir H. T. De la Beche, Dr. W. Smith, and Mr. C. H. Smith, visited one hundred and five quarries, and examined one hundred and seventy-five edifices; and their collected specimens were then submitted to tests, both mechanical and chemical, by Professors Daniell and Wheatstone, of King's College, London. In order to leave a permanent record of their labours, the Commissioners published a Report, and deposited in the Museum of Economic Geology, a variety of specimens of the stones which they had collected. From this Report, we select such details as are calculated to serve the purposes of popular instruction.

The Commissioners did not consider it necessary to extend their inquiries to granites, porphyries, and other stones of similar character, on account of the enormous expense of converting them to building purposes in decorated edifices, and from a conviction that an equally durable, and in other respects more eligible material, could be obtained for the object in view from among the limestones or sandstones of the kingdom.

The Commissioners soon had striking proofs of the necessity and importance of this inquiry in the lamentable effects of decomposition observable in the greater part of the limestone employed at Oxford; in the magnesian limestones of the Minster, the other churches, and public buildings at York; and in the sandstones of which the churches and other public edifices at Derby and Newcastle are constructed; and numerous other examples. The unequal state of preservation of many buildings often produced by the varied quality of the stone employed in them, although it may have been taken from the same quarry, showed the propriety of a minute examination of the quarries themselves, in order to gain a proper knowledge of the particular beds from whence the different varieties have been obtained. An inspection of quarries was also desirable for the purpose of ascertaining their power of supply, and other important matters; for it frequently happens, that the best stone in quarries is neglected, or only partially worked, in consequence of the cost of laying bare, and removing those beds with which it may be associated; whence it happens, that the inferior material is in such cases supplied.

Stone decays more rapidly in towns than in the open country, where dense smoke, fogs, and vapours,, which act injuriously on buildings, do not exist. There is also another curious cause which contributes to the durability of stone buildings situated in the country. In the course of time, the stone becomes covered with minute lichens, which, though in themselves decomposing agents, act with extreme slowness, and when once firmly established over the entire surface of the stone, seem to exercise a protective influence, by defending the surface from the more violent destructive agents: whereas, in

populous smoky towns, these lichens are prevented from forming, and thus the stone is exposed to severer trials than stone of the same kind situated in the country.

As a remarkable illustration of the difference in the degree of durability in the same material, subjected to the effects of the air in town and country, the appearance. is noticed of several frusta of columns, and other blocks of stone, that were quarried at the time of the erection of St. Paul's Cathedral, London, and which are now lying in the Isle of Portland, near the quarries from whence they were obtained. These blocks are invariably found to be covered with lichens, and, although they have been exposed to all the vicissitudes of a marine atmosphere for more than one hundred and fifty years, they still exhibit beneath the lichens their original form, even to the marks of the chisel employed upon them; whilst the stone which was taken from the same quarries, (selected no doubt with equal, if not greater care, than the blocks alluded to,) and placed in the Cathedral itself, is, in those parts which are exposed to the south, and south-west winds, found, in some instances, to be fast mouldering away.

Colour is more important in the selection of a building stone to be situated in a populous and smoky town, than for one to be placed in the open country, where all edifices become covered with lichens; for, although in such towns, those fronts which are not exposed to the prevailing winds and rains, will soon become blackened, the remainder of the building will constantly exhibit a tint depending upon the natural colour of the stone.

The chemical action of the atmosphere produces a change in the entire matter of the limestones, and in the cementing substance of sandstones, according amount of surface exposed to it. The particles of the stone first loosened by the action of frost are removed by powerful winds and driving rains. The buildings in this climate were generally found to suffer the greatest amount of decomposition on their south, south-west, and west fronts, arising doubtless from the prevalence of winds and rains from those quarters.

Those buildings which are highly decorated, such as the churches of the Norman, and pointed styles of architecture, generally afford a more severe test of the durability of a building stone, than the more simple and less decorated castles of the fourteenth and fifteenth centuries; because, in the former class of buildings, the stone is worked into more disadvantageous forms than in the latter, as regards exposure to the effects of the weather. Buildings in a state of ruin, from being deprived of their ordinary protection of roofing, glazing of windows, &c., afford an equally severe test of the durability of the stone employed in them.

The durability of various building stones in particular localities was estimated by examining the condition of the neighbouring buildings constructed of them. Among sandstone buildings were noticed the remains of Ecclestone Abbey, of the thirteenth century, near Barnard Castle, constructed of a stone closely resembling that of the Stenton quarry, in the vicinity, in which the mouldings and other decorations were in excellent condition. The circular keep of Barnard Castle, apparently also built of the same material, is in fine preservation. Tintern Abbey is noticed as a sandstone edifice, that has to a considerable extent resisted decomposition. Some portions of Whitby Abbey are fast yielding to the effects of the atmosphere. The older portions of Ripon Cathedral; Rivaulx Abbey; and the Norman keep of Richmond Castle, in Yorkshire, are all examples of sandstone buildings, in tolerably fair preservation.

Of sandstone edifices in an advanced state of decomposition, are enumerated Durham Cathedral, the churches at Newcastle-upon-Tyne, Carlisle Cathedral, Kirkstall Abbey, and Fountain's Abbey. The sandstone churches of Derby are also extremely decomposed; and the church of St. Peter's, at Shaftsbury, is in such a state

[JANUARY 20, 1844.

wear well.

The excellent condition of the parts which remain of Glastonbury Abbey shows the value of a shelly limestone similar to that of Doulting; whilst the stone employed in Wells Cathedral, apparently of the same kind, and not selected with equal care, is in parts decomposed.. In Salisbury Cathedral, built of stone from Chilmark, we have evidence of the general durability of a siliciferous limestone; for, although the west front has somewhat yielded to the effects of the atmosphere, the excellent condition of the building generally is most striking.

The materials employed in the public buildings of Oxford afford a marked instance both of decomposition and durability; for whilst a shelly oolite, similar to that of Taynton, which is employed in the exposed parts of the more ancient parts of the Cathedral, in Merton College Chapel, &c., is generally in a good state of preservation, a calcareous stone from Heddington. employed in nearly all the colleges, churches, and other public buildings, is in such a deplorable state of decay as, in some instances, to have caused all traces of architectural decoration to disappear, and the ashler* itself to be, in many places, deeply disintegrated.

In Spofforth Castle two materials, a magnesian limestone and a sandstone, have been employed; the former in the decorated parts, and the latter for the ashler, and although both have been equally exposed, the magnesian limestone has remained as perfect in form as when first employed, while the sandstone has suffered considerably from the effects of decomposition. In Chepstow Castle a magnesian limestone is in fine preservation, and a red sandstone rapidly decaying. A similar result was observed in Bristol Cathedral, which afforded a curious instance of the effects of using different materials; for a yellow limestone and a red sandstone have been indiscriminately employed both for the plain and the decorated parts of the building; not only is the appearance unsightly, but the architectural effect of the edifice is also much impaired by the unequal decomposition of the two materials.

After enumerating these and other examples, the * The ashler is the plain facing of the walls.

account of their more general uniformity of tint, their comparatively homogeneous structure, and the facility and economy of their conversion to building purposes; and, of this class, preference is given to those which are most crystalline. Professor Daniell is of opinion that the nearer the magnesian limestones approach to equivalent proportions of carbonate of lime and carbonate of magnesia, the more crystalline and better they are in every respect.

It was considered that this crystalline character, together with durability, as instanced in Southwell Church, &c.; uniformity in structure; facility and economy in conversion; and advantage in colour, were all comprised in the magnesian limestone, or dolomite of Bolsover Moor and its neighbourhood; and this was accordingly recommended as the most proper material to be employed in the new Houses of Parliament+ This opinion was not arrived at, nor this recommendation made, until after a very extensive series of experiments had been completed by Professors Daniell and Wheatstone upon specimens of the stones of the various quarries visited by the Commissioners. The specimens, as delivered to these gentlemen, were in the form of two-inch cubes. comprehensive kind. These experiments were of a most was determined by chemical analysis:-their specific The composition of the stones gravities; their weights after having been perfectly dried by exposure in heated air for several days; then their weights after having been immersed in water for being to ascertain the absorbent powers of the stones, several days so as to become saturated; the object under the exhausted receiver of an air-pump. The which was further tested by placing them in water stones were also subjected to the process of disintegration, invented by M. Brard, the object of which is to determine, by easy experiments, whether a building stone will or will not resist the action of frost. it at length in a separate article. Lastly the coheprocess is so curious and valuable that we will state sive strength of each specimen, or its resistance to This weight was furnished by a hydrostatic press, the pressure, was tested by the weight required to crush it. the end of the pump lever produced a pressure on the pump of which was one inch in diameter: one pound at surface of the cube equal to 2·53 cwt., or to 71·06 lbs. on the caution, the weight on the lever was successively insquare inch. These trials were made with creased by a single pound, and, in order to ensure a gradual action, a minute was allowed to elapse previous to the application of each additional weight. It was noted for each specimen the pressure at which the stone began to crack, and also the pressure at which it was crushed.

This

The results of all these experiments (which are stated for each stone), gave a decided preference to the Bolremarkable for its peculiarly beautiful crystalline strucsover magnesian limestone, which was noticed as being ture, while it was the heaviest and strongest of all the specimens, and absorbed least water. Its composition was 50 per cent of carbonate of lime, and 40 of carbonchiefly of silica and alumina. ate of magnesia; the remaining ten parts consisting

JOHN W. PARKER PUBLISHER, WEST STRAND, LONDON.