limestone; south side highly enriched with zig-zag and other ornaments; the columns are gone; the parts which remain are in good condition. St. Margaret's Church (15th century), of magnesian limestone; east front much exposed, and in good condition. The porch is of Norman date, and has been reconstructed; four bands of enrichment in the head, in tolerably fair condition, but many stones, particularly those of a deep yellow brown colour, are much decomposed. The other churches of York (which are of the 14th and 15th centuries) are built of magnesian limestone, and are generally in an extremely decomposed state; in many instances all architectural detail is obliterated. Modern Buildings: THE MUSEUM, of Hackness sandstone, built nine years since, much decomposed wherever it is subject to the alternation of wet and dry, as at the bottom of the columns of the portico, plinth, &c. THE CASTLE (recently erected); the plinth of the boundary wall (which is of Bramleyfall sandstone) already exhibits traces of decomposition. York Savings Bank. Huddersfield stone (?), in good condition. WORKSOP CHURCH (principally of the 13th century), of a siliciferous variety of magnesian limestone and of a sandstone; in very unequal condition. Some parts are very much decomposed, whilst others are in a perfect state. 1666. Valuable as the above Report is, there remain points, perhaps minor ones, which are still desiderata for the architect; but we are, nevertheless, much indebted to all concerned in its production. It contains a sufficiently ample account of the principal quarries of the country to guide the architect in the choice of the material, and is almost the only thing that the government of this country has ever done to advance architecture as a science for it, as an art, it does not appear probable much will be done till things are very much changed. We shall close our account of the stone of England with a very useful table of the chemical analysis of sixteen specimens of stone, which were examined by Messrs. Daniel and Wheatstone, whose names are sufficient to impart a value to it in the mind of every scientific person. 0-0 Of dry masses 1.20 0.0 2.53 0.8 0.0 0.0 51.1 40.2 54 19 57.5 55.7 93 59 0.0 2.90 2.50 1.20 4.10 3.8 3.7 52 98.3 96-40 95 1 93-1 49:4 3.6 2232 2628 2229 2247 2338 2316 2147 2134 2138 2182 Cohesive Powers. 1839 2145 2045 2090 2481 2260 2627 2621 2695 117 61 55 「 61 |། 33 | 21 | 30 1667. The above table gives the results of the chemical analysis of sixteen specimens of stone, arranged according to their respective classes. The names of the quarries are inserted under the general divisions of the different species of stone, and the specimens were considered as fair average samples of the workable stone in such quarries. The experiments were conducted by Messrs. Daniel and Wheatstone. In subsection 1500. we have already supplied a table, to which the reader is referred for the crushing weights of the stones therein mentioned; and that, added to the information which the immediately preceding pages supply, will, we trust, be all that is necessary on this branch of the subject under consideration. 36 36 25 101 57 SECT. II. GRANITE. 1668. Among the primitive rocks of the globe, whose period of creation is considered by geologists as antecedent to that of organic beings, is that of granite, whose use in architecture seems to bid defiance to time itself. The term granite appears to be a corruption of the Latin word geranites, used by Pliny to denote a particular species of stone. Tournefort, the naturalist, in the Account of his Voyage to the Levant in 1699, is the first of modern writers who uses the name. The word seems to have been applied by antiquaries to every granular stone susceptible of use in architecture or sculpture, in which vague sense it was used by mineralogists, until about fifty years since, when true granite was classed as a particular mountain rock. Its constituent parts are concretions of felspar, quartz, and mica, intimately joined together, but without any basis or ground. These parts are variable in quantity, so that sometimes one, sometimes the other, and frequently two of them, predominate over the third. The felspar, however, generally predominates, as mica is the least considerable ingredient of the rock. In some varieties the quartz is wanting, in others the mica; but where these peculiarities occur, the granites must be considered as varieties, not as distinct species. 1669. The constituent parts differ in their magnitude, alternating from large to small and very fine granular. The colour, moreover, is very variable, depending principally on the predominating ingredient, the felspar, the quartz, and the mica having usually a grey colour. The felspar is mostly white, inclining to grey and yellow, sometimes red, and even also milk white, sometimes flesh-red; rarely grey, yellow, or green. The quartz is usually grey, seldom milk-white, and always translucent. The mica is usually grey, and sometimes nearly black. The felspar in granite has usually a vitreous lustre, and of perfectly foliated fracture; yet in some varieties it passes into earthy, with the loss of its hardness and lustre ; in other words, it has passed into porcelain earth. The appearance in question is sometimes produced by the weathering of the felspar, and sometimes it appears to be in its original state. When pyrites are found in the veins which traverse granite, the vicinous felspar and mica are converted into a species of steatitical matter by the action of the sulphuric acid formed during the decomposition of the pyrites. The mica also is liable to decomposition from exposure to the atmosphere, but the quartz never alters. In Cornwall, there is a considerable portion of the granite in which earthy felspar is found. 1670. Granite is not decomposed by acids, and is only imperfectly and slowly calcinable in a great heat. Those species which contain much white felspar, and only a small portion of quartz, like the greater part of the granites of Cornwall and Devonshire, are liable to decomposition much sooner than many of the Scotch granites, in which the quartz is more abundant, and equally disseminated. In the selection of the Cornish and Devon granites, those are to be preferred which are raised in the largest blocks and are easiest worked, which, for common purposes, answer well enough, such as for paving-stones and the like; but harder granite must be sought for than Devonshire or Cornwall produces, where the construction is of importance; for the masses in these counties are mostly in a condition of rapid disintegration and decay, which seems chiefly attributable to their containing a large portion of potass. The Naval Hospital of Plymouth is built of a granite whose parts appear to have been well selected. It was erected upwards of seventy years since, and, except in the columns of the colonnades, does not exhibit symptoms of decay. In these, on their more exposed sides, the disintegration of the felspar has commenced, and lichens have already attached their roots to some parts of the surfaces. 1671. The grey granite, or moorstone as it is called in Cornwall, is got out in blocks by splitting it with a number of wedges applied to notches pooled in the surface of the stone about four inches apart. The pool holes are sunk with the point of a pick, much in the same way as other hard quarry stones are split. The harder the moorstone the nearer it can be split to the scantling required. All granite may be wrought, and, indeed, is wrought into mouldings by means of pointed tools of various weights and sizes; but it is first roughed out by means of heavy hammers, whose shape is formed by two acute angled triangles, joined base to base by a rectangle between them, thus O Red granite, sometimes yellowish, and generally interspersed with black mica, is found in Devonshire, and indeed at Mount Edgcumbe there are fine tables of it equal to the finest oriental granite, and it is found also in other parts of England; but for hardness, and in works where durability is indispensable, the granite from Aberdeen and Dundee is to be preferred by the architect. produces. These take an admirable polish, and are superior to all others which the island Of these the red generally is harder than the grey sorts, but more difficult to The Peterhead, from the vicinity of Aberdeen, is perhaps the best, and it is, morein appearance, the most beautiful which Scotland affords; indeed, in point of beauty, work. over, 1672. The common granite is the material chiefly used for paving the roads of the metropolis. A cubic foot of Aberdeen grey granite weighs 166 lbs. Aberdeen red granite Cornish red granite 165 166 164 SECT. III. MARBLE. 1673. With the architect and sculptor the name of marble is applied to all stones, harder than gypsum, which are found in large masses, and are susceptible of a good polish. On this principle, under the head of marble, are included many varieties of limestone, porphyry, and even granite and fine-grained basalts. But with mineralogists the word is used in a much more restricted sense, and is confined to such varieties of dolomite, swinestone, and compact and granularly foliated limestone as are capable of receiving a good polish. 1674. The external characters are as follows: colours white, grey, red, yellow, and green. Has generally but one colour, though it is often spotted, dotted, striped, and veined. Occurs massive, and in angulo-granular distinct concretions. Internally it alternates from shining to glistening and glimmering; lustre intermediate between pearly and vitreous. Fracture foliated, but oftentimes inclining to splintery. Fragments indeterminate, angular, and rather blunt-edged. More or less translucent. Brittle, and easily frangible. Its chemical characters are, that it generally phosphoresces when pounded, or when thrown on glowing coals. It is infusible before the blow-pipe. Dissolves with effervescence in acids. 1675. All the varieties may be burnt into quicklime; but it is found that in many of them the concretions exfoliate and separate during the volatilization of their carbonic acid, so that by the time that they become perfectly caustic, their cohesion is destroyed, and they fall into a kind of sand, a circumstance which renders it improper to use such varieties in a common kiln. The most important use, however, of marble is as a material for decoration. 1676. The varieties of marble are almost infinite, and their classification would be perhaps useless here. Among those in use with the ancients, the white marble of mount Penteles in Attica, thence called Pentelican, seems to have held the first rank. It was used in the Parthenon and other buildings in Athens, and was also in high repute with the Greek sculptors. The Parian marble of the finest description was obtained from Mount Marpessus in the island of Paros, whence it was also called Marpessian marble. This sort was also highly esteemed. The Parian marble was sometimes termed Lychneus, from its employment for candelabra, and Lygdinum, from the promontory of Lygdos. Another marble of antiquity was that from Mount Hymettus in Attica. Thasus and Lesbos produced white marbles, much esteemed; and the latter also a marble of a black colour. But a marble whiter than even that of Paros was found at Luna in Etruria. Amongst the white marbles also was the Marmor Phellense from Mount Phelleus; Coraliticum, from the neighbourhood of the river Coralios in Phrygia, termed also Sangarium, from a different name of the same river; and the Cyzicum, from the quarries of Cyzicus in Asia Minor. The Chernites resembled ivory in its colour. Among the black marbles were the Synnadicum, or Phrygium, from the vicinity of the city of Synnada in Phrygia; that of Tanarus, the Marmor Libicum, or Numidian, also called Luculleum, called by the French noir antique or rouge antique. Of a transparent black colour also was the celebrated Chium Marmor, from Mount Pelineus in the island of Chios. The Marmor Obsidianum, from Ethiopia, was also black. Of the same colour, but veined, was that from the isle of Proconesus, called Proconesian or Cyzican marble. Mount Taygetes produced the Marmor Laconicum, of a green colour, more generally now known by the name of verd antique. That of Carystus was of a mingled green. The Atraicum Marmor, from Mount Atrax in Thessaly, was a mixture of white, green, blue, and black. The Tiberian and Augustan marbles were from Egypt, and of a green colour. That of a dark green, which is called serpentino antico, from the alleged resemblance of its colour to the skin of a serpent, was anciently called Marmor Aphites or Memphites, and was obtained, as its second name imports, from the neighbourhood of Memphis. The Corinthian was a yellow marble; the Phingites, from Cappadocia, white with yellow spots. The Rhodian was marked with spots of a golden appearance; and that of Melos, obtained from Mount Acynthus, was also yellow. 1677. The Parian marble, above mentioned, consists almost entirely of carbonate of lime; that of Carrara, in Italy, is often mixed with granular quartz in considerable proportion. Dr. Clarke says that while the works in Parian marble remain perfect, those in Pentelic marble have become decomposed, and sometimes exhibit a surface as earthy and rude as that of common limestone. This is considered to be principally owing to veins of extraneous substances which intersect the Pentelic quarries, and which appear more or less in all the works executed in this kind of stone. The Parian marble has a waxy appearance when polished; it hardens by exposure to the air, and must be held in estimation even now, as the material from which were formed the Venus di Medici, the Diana Venatrix, the colossal Minerva Pallas of Velletri, and the Capitoline Juno. The marbles known by the names of Verde antico and Verde di Corsica are composed of limestone, calcareous spar, serpentine, and asbestus. 1678. The marbles of France are many of them extremely beautiful, but their use is chiefly confined to that country. 1679. The marbles of the British Islands deserve more notice from the English architect than they have hitherto received. In England there are but few as yet quarried of granular foliated limestone, the greater number of varieties of them belonging to the flatz or secondary limestone. Derbyshire and Devonshire abound with marble; but the most remarkable, and perhaps most beautiful, of the English marbles, is that of Anglesea, called Mona marble, and much resembling Verd antique. Its colours are greenish black, leek green, and sometimes purple, irregularly blended with white, but they are not always seen together in the same piece. The white part is limestone, the green shades are said to be owing to serpentine and asbestus. The black marbles found in England are varieties of lucullite. 1680. Of the Scotch marbles the principal are the Tiree, of which there are two varieties, red and white. The Iona, whose colours are a greyish white and snow white, sometimes intermixed with steatite, which gives it a green or yellow colour in spots known under the name of Iona or Icolmkill pebbles. It does not take a high polish. The Skye marble, of greyish hue, with occasionally various veins. The Assynt varieties of white, of grey, and dove colour. Glen Tilt marble, white and grey, with occasionally yellow and green spots. Marble of Balliculish, of a grey or white colour, and capable of being produced in considerable blocks. Boyne marble, grey or white, and taking a good polish. Blairgowrie, in Perthshire, of a pure white colour, fit, it is said, to be employed in statuary and for architectural purposes; and Glenavon, a white marble, said by Williams (Natural History of the Mineral Kingdom) to be a valuable marble, is not used, from the remoteness of its situation and the difficulty of access to it. 1681. The black marbles of Ireland, which have of late been much introduced for architectural purposes, are lucullites. In the county of Waterford are several kinds. At Toreen is a fine variegated sort of various colours, viz., chesnut brown, white, yellow, and blue, and taking a good polish. A grey marble, beautifully clouded with white, and susceptible of a good polish, has been found near Kilcrump, in the parish of Whitechurch, in the same county. At Loughlougher, in the county of Tipperary, a fine purple marble is found, which is said to be beautiful when polished. Several variegated marbles are described by Smith in the county of Cork, but it does not appear certain whether these and others are granular limestone. The county of Kerry affords several variegated marbles, such as that found near Tralee. Marble of various colours is found in the same county, in the islands near Dunkerron, in the river of Kenmare: some are purple and white, intermixed with yellow spots; and some beautiful specimens have been seen of a purple colour, veined with dark green. 1682. The principal part of the supply to England of foreign marble is from Carrara, a small Italian town in the duchy of Massa. The quarries at this place were celebrated from an early period, and spots are still shown about them whence they dug the marble for the Pantheon. Masses of marble are sometimes procured here nine feet in length and from four to six in breadth. The marble produced besides the white statuary is of different colours and veins. The quarries are the property of the principal inhabitants of the town, who carry on an extensive trade in the article; but the difficulty of choosing the marble has induced artists to settle there for the execution of their works, and the consequence is, that sculpture abounds and flourishes in the town. 1683. There is a beautiful species of yellow marble obtained from the quarries near Siena, but the quantity imported is not very great. SECT. IV. TIMBER. 1684. The information we propose here to lay before the reader relative to the different species of timber is extracted from Miller's Gardener's Dictionary, Rondelet's Art de Bàtir, Rees's Cyclopædia, and Hunter's edition of Evelyn's Sylva. To give any thing like the information that would satisfy the botanist would be out of place in an architectural work; and we therefore confine our observations to those which will be useful to the student. 1685. OAK. Of this most valuable timber for building purposes Vitruvius (lib. ii. cap. ix.) enumerates five species, which it would now be difficult to identify. That some species of the Quercus of the botanists are more valuable for building purposes than others no doubts exist. Evelyn seems to commend especially the Irish oak, because of its withstanding the efforts of the worm; but it is not easy to ascertain the particular species to which he alludes. In the present day the Sussex oak is esteemed the most valuable; a value, according to some authors, derived from the nature of the soil and from good management in the culture, which is an object of no small importance. 1686. Generally, it has been usual to consider England as producing, without difference in quality, but one species of oak; but two sorts are well known to the English botanist, the Quercus Robur and the Quercus jessiflora. The former is found throughout the temperate parts of Europe, and is that most common in the southern parts of England. Its leaves are formed with irregular sinuosities, and their footstalks are short, occasionally almost without any at all. It attains a very large size, and the wood is tolerably straightgrained and pretty free from knots, in many instances resembling the German species I called wainscot. It is easily split for making laths for plasterers and slaters, and is beyond doubt the best sort for joists, rafters, and other purposes where stiff and straight-grained timber is a desideratum. In the Quercus jessiflora, which, though found about Dulwich and Norwood, according to Miller, appears to be the common oak of Durham, and perhaps of the north of England, the leaves have long footstalks, frequently an inch in length, and their sinuosities are not so deep, but are more regular than those of the Robur just described. The acorns are so close to the branches as to have scarcely any stalks. The wood is of a darker hue, and the grain is so smooth that it resembles chesnut. Than the Robur it possesses more elasticity, hardness, and weight, but in seasoning it is subject to warp and split; hence unfit for laths, which in the north of England are rarely of oak. There is no reason for supposing, as has been conjectured, that the oak of the Gothic roofs of the country is of this species, though we are aware of the great durability of the oak in the buildings in the northern part of the island. 1687. The specific gravity of the species first named, that is, the Quercus Robur, may be taken at about 800, and the weight of a cube foot 50·45 lbs. That of the last-named at 875, and the weight of a cube foot at about 55 00 lbs. Their cohesive force and toughness are proportionable. 1688. The American species scarcely claim a notice here, because their use in England is, from every circumstance, out of the question. Of the red oak of Canada (Quercus rubra), the only one of which the use could be contemplated, we merely observe, that it is a light, spongy, and far from durable wood, though, in the country, in many instances useful. Its growth is rapid, and it rises to the height of 90 or 100 feet. 1689. There is a species of oak imported from Norway, which has received the name of clapboard, and another imported from Holland, known under the name of Dutch wainscot, though grown in Germany, whence it is floated down the Rhine for exportation. The latter is destitute of the white streaks which cross the former, and is thereby distinguished from it. The use of these woods has latterly much diminished in England. They are both softer than common oak, and the clapboard far inferior to wainscot. They are more commonly used for fittings and fixtures, whereto they are well adapted. In damp situations, oak decays gradually from its external surface to the centre of the tree; the ring on the outside, which it acquired in the last year of the growth of the tree, decaying first; but if the tree be not felled till past its prime, its decay is reversed by its commencement at the centre. An oak rarely reaches its prime under the age of an hundred years; after that period, which is that of its greatest strength, it cannot be considered as fit for building purposes; and, indeed, it may be taken as a rule, that oak before arriving at its maturity is stronger than that which has passed it. 1690. If the architect has the opportunity of selecting the timber whilst in a state of growth, he will, of course, choose healthy, vigorous, and flourishing trees. Those in which the trunks are most even are to be preferred. A mark of decay is detected in any swelling above the general surface of the wood. Dead branches, especially at the top of the tree, render it suspicious, though the root is the best index to its soundness. notion of Alberti (De Re Edificatoria), of using all the timber in the same building from The |