Part 7
I have devoted some considerable time to an investigation of the internal structure of sandstones, which I have communicated from time to time to various scientific societies and publications, and will now briefly explain it in a manner I judge will be most likely to interest architects and engineers. The particles or grains of which the rock is built up are of various forms and sizes, from a thoroughly rounded grain, almost like small shot, to a broken and jagged structure, and to others possessing crystalline faces. These grains, most of them possessing a longer axis, have been rolled backwards and forwards by the tides or by river-currents. The larger grains naturally lie on their sides when freshly deposited, with their axes in the plane of bedding; the smaller and more rounded particles naturally tend to occupy the interstices between the others, and in this way rude divisional planes or laminations are formed. Each layer forms a sort of course like coursed-rubble in a wall, and by the necessities of deposition a certain rude geometric arrangement results, by which the particles of the future rock overlap each other, and thereby gain what is known to architects as bond.
But, so far, this is only like "dry walling," the mass wants cementing together to make it solid. The cementing process happens in this way in our rocks, which are almost purely silicious: Water containing a minute quantity of carbonic acid in solution, which most rain-water does, especially when it comes into contact with decaying vegetation, has the power of dissolving silica to a slight extent. This is proved in various ways, and is shown in the fact that all river water contains more or less silica in solution.
The circulation of water through the sand deposit of which our rocks are made dissolves part of the grains, and the silica taken up is redeposited on others. I cannot explain the chemical reaction that produces this deposition, but that it takes place in the rock during some period of its history is certain. I exhibit a quartzite pebble taken from the Triassic sandstone at Stanlow Point, which, as can be easily seen, was at one time worn perfectly smooth by attrition and long-continued wear, for the quartzite is very hard. Upon this worn surface you will see spangles and facets which reflect the light, and on closer inspection it will be evident that they are crystals of quartz that have been deposited upon the surface of the worn pebble after it became finally enclosed in the rock.
A microscopic examination of the granules of the rock itself will show that many of them have had crystalline quartz deposited upon their surfaces, and in some cases rounded grains have in this way become almost perfect crystals.
An examination of the best sandstones for building purposes shows that they possess more of these crystalline particles than the inferior ones, and a good silicious sandstone shows its good quality by a fresh fracture sparkling in the sun. In addition to these crystalline deposits of silica I believe it exists also as a cement which binds the particles together when in contact.
It certainly is, however, with this secondary silica that the original sand has become a building stone, and the particles have become interlaced and bound together. Thus, in building parlance, the grains are the rubble of the wall, the currents the quarrymen, masons and laborers, and the silicious infiltration the mortar.
And now, when I am on the subject, I may point out that this hard and compact quartzite pebble was also once loose sand. The only difference between the sandstone in which it was imbedded and itself is that in the latter case the process of silicious deposit has gone further, so that all the interstices between the grains have been absolutely filled up with the cement.
It is not possible to see this clearly with the naked eye, but by the aid of a slice of the rock prepared for the microscope the granular structure of the quartzite is made perfectly plain. So much for the mechanical, chemical, and molecular structure of sandstone, all of which affect the strength and quality of the stone; but to architects there is another element of consequence, namely, the color. The rich red of our Triassic sandstones is due to a pellicle of peroxide of iron coating each of the grains. That this is merely surface coloring is shown by the fact that hydro-chloric acid will discharge the color and leave the grains translucent. Unfortunately the most brilliantly colored stone is not the most durable, and it so happens that these brilliant red sandstones are often composed of exceedingly rounded grains. Also some of the very red sandstone has an interfilling of a loose argillaceous irony matter detrimental to the stone as a building stone. The most durable of the red sandstones are those having a paler or grayer hue, like those of Woolton, Everton, and Runcorn. This distinction of color was brought freshly to my mind a short time since in looking at the church of Llandyrnog, in the Vale of Clwyd, a few miles from Ruthin. Some of the dressings, quoins for instance, were of a very brilliant-colored red sandstone, and others of a pale gray or purple red. It struck me that these latter must be of Runcorn stone, which I was afterwards informed was the case. The very red stone was the natural stone of the Vale, originally used for dressings, which were replaced, on the restorations being made, with Runcorn stone. The original stone was æsthetically the best, but the introduced stone the best structurally. The old stone of Chester Cathedral was a very red Bunter sandstone, which decayed badly. It has been replaced in the restorations by Runcorn stone, which belongs to the Keuper division, which has caused the Geological Surveyors to say that the Keuper is a better building stone than the Bunter. In this case it is; but, on the other hand, the Bunter sandstones, or Pebble-beds, as they are called, near Liverpool, are often better than the Runcorn Keuper. The Runcorn building stone lies between two beds of very red loose rock, showing that it is not its geological position, but its _structure_, that makes it a good durable stone.
It is a remarkable fact that most of the pebbles included in the red rocks are quartzites, or indurated silicious sandstones; and, as showing that their solidity and hardness are due only to a further continuance of the deposit of silica in the interstices, it has been proved that the purple quartzites are purple only by reason of the original coloration of the grains which have been enclosed between the original grains and the secondary silica. Yellow sandstone is colored also by iron, and I have frequently seen the red sandstone shading of to the yellow without any division whatever. The various shades and tints of sandstone are necessarily due to the coloration of the individual grains.
Most of you will, no doubt, have observed the sort of marbling or grain upon the stone of our old buildings, such as the Town-Hall, which I believe was obtained from quarries occupying the site of the St. James's Cemetery. This is due to what is called current bedding; that is to say, the grains have been arranged along oblique lines and curves instead of in parallel laminæ. This stone, which is geologically equivalent to the Storeton Stone, and of the same nature, has stood very well. Some of the Storeton Stone, if free from clay galls, although very soft when quarried, becomes hardened by exposure, and will stand the weather much better than a harder and more pretentious material.
The stone of Compton House is in a very good condition, although the mason told me such was the hurry in rebuilding that they could not stop to select the stone, and also that it is placed in all sorts of positions with respect to its quarry bed. Perhaps the circumstances that the stone is not in parallel laminæ may have something to do with its durability, notwithstanding this latter fact.
It would take a long Paper, and several evenings, to exhaust the subject even of our local stones. I may mention, however, that the quarries of Grinshill, between Shrewsbury and Hawkstone, yield a beautiful white sandstone, of a finer grain than Storeton, but of a similar quality.
Most of the public buildings of Shrewsbury are built of it, and I am informed that it was to some extent used in the Exchange buildings. The rocky substratum of a district can be well seen in its ancient buildings, for in old times carriage was so important an item that the old builders could not go far for their stone; hence we see that the old churches of part of Lancashire and most of Cheshire, and a large portion of Shropshire, are of red sandstone. Some of it has stood very well, while some has decayed into shapeless masses. There is a tendency to exfoliate parallel to the exposed or worked surface, in all stones, irrespective of the way of the bed, but more so where the stone is set up on edge, or at right angles, to its quarry bed. It is interesting and peculiar to see in some of the old buildings erected with pebbly sandstone how the white quartz pebbles stand out from the surface like _warts_. This is due to the greater indestructibility of the quartz pebbles, and the weathering away, or denudation, of the sandstone face.
Before leaving the subject of local sandstones it will be necessary to refer to one quality they have which is of excellent utility as regards the storage of water, but which is decidedly a disadvantage in building stone--that is, their porosity. I have proved by actual experiment that a cubic foot of Runcorn Stone will take up three quarts of water by capillarity, and that it is possible to make a syphon of solid sandstone which will empty a vessel of water into another vessel by capillarity alone.[2] This shows the absolute necessity of damp-proof courses, not only in the main walls of buildings of stone, but even in fence walls, for the continual sucking up of moisture from the earth, and its evaporation at the surface of the stone, make it rapidly decay. I think I could show you this fact in almost any stone building in Liverpool or elsewhere where the stone is in direct connection with the earth. It also shows the necessity of taking care that no stones go through the wall to the interior surface, and of precautions for backing up stone walls with less porous materials, or the introduction of a cavity. If you could suppose such a sandstone wall 40 feet long, 20 feet high, and 1 foot 6 inches thick fully saturated, it would hold almost a ton of water! Of course, it never would be fully saturated, because of the evaporation from the surfaces, but with a southwest aspect, and very wet weather, it might become half saturated. But what does evaporation mean? It means the loss of so much heat and the burning of so much coal to supply its place. From this it will be seen that a pure sandstone wall is a thing to be avoided.
The subject is so wide a one that I have felt compelled to restrict my remarks to local sandstones, but the general principles of structure apply to all sandstones alike.
It is difficult by written description to tell you how to select a good stone, but one essential is that there shall be a good deposition of secondary quartz, as shown by the crystalline sparkling on the freshly fractured surface.
It must also be free from very decided laminations, for these constitute planes of weakness and are often indications of the deposition of varying materials, or the same material in various grades of fineness. It must also not be full of argillaceous and iron-oxide infillings. It should possess a homogeneous texture. The best way to study building stones is to study them in old buildings, for nature has then dissected their weaknesses.
FOOTNOTES:
[1] Read before the Liverpool Architectural Society, on the 18th November, 1889, by Mr. T. Mellard Reade, F.S.G.S. _Fellow_, President of the Society, and printed in the _R.I.B.A. Journal_.
[2] This experiment was made before the audience.--T. M. R.
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WARFARE ON OAK TREES.--"The world seems to have waged a special warfare upon oak trees," says a St. Louis man. "Before iron ships were built, and that was only twelve years ago, oak was the only thing used. When this drain ceased oak came into demand for furniture, and it is almost as expensive now as black walnut. No one feels the growing scarcity of oak like the tanner, and the substitution of all sorts of chemical agencies leads up to the inquiry as to whether other vegetable products cannot be found to fill the place of oak bark. The wattle, a tree of Australian growth, has been found to contain from twenty-six to thirty per cent of tannic acid. Experiments have been made on the Pacific Slope, where the wattle readily grows, and in a bath of liquor, acid was made from it in forty-seven days, whereas in liquor made from Santa Cruz oak, the best to be found in all the Pacific States, the time required is from seventy-five to eighty days. The wattle will readily grow on the treeless plains of Texas, New Mexico and Arizona, the bark of which ought to yield five dollars per acre counting the fuel as nothing."--_Invention._
THE BARYE EXHIBITION.
[Illustration]
Entering the handsome galleries of the American Art Association, one finds the lower floor given up to the Barye bronzes, while the upper rooms are devoted to the "Angelus" and the paintings by Millet and other contemporaries of the great French sculptor. Passing on the left of the entrance the superb, large bronze of "Theseus battling with the Centaur," one is fronted by the great cast of the "Lion and Serpent," which from the centre of the gallery dominates the surrounding exhibits. Both of these are the property of the Metropolitan Museum of Art, the cast having lately been presented to that institution by the French government. Upon the right hangs Bonnat's vigorous portrait of Barye, on the left wall one sees the water-color of the "Tiger Hunt," and all around are cases, groups and isolated pieces of the bronzes.
Here are over 450 works in wax, plaster and bronze, of which Mr. W. T. Walters contributes one-fourth, while the Corcoran Gallery sends its entire collection, numbering nearly a hundred, Mr. Cyrus J. Lawrence loans sixty-two pieces, Mr. James F. Sutton fifty-two and Mr. Samuel P. Avery thirty. Other contributors, who have followed their generous example, are Messrs. R. Austin Robertson, Theodore K. Gibbs, Robert and Richard M. Hoe, James S. Inglis, Richard M. Hunt and Albert Spencer. Of many of the subjects there are several copies, and amateurs can study proofs and patinas to their heart's content. From Mr. Walters's famed collection are the four unique groups modelled for the table of the Duke of Orleans, chief of which is the "Tiger Hunt," where two of the huge cats attack an elephant from whose back three Indians defend themselves with courage. The giant pachyderm writhes his serpent-like trunk in air and plunges forward open-mouthed, trumpeting with pain from the keen claws of the tigers hanging on his flanks. The Hunts of the Bull, the Bear and the Elk are worthy companions of this magnificent bronze, offering wonderfully fine examples of condensed composition in the entwined bodies of men and beasts, and filling the eye with the grand sweeps of their circling forms. The same liberal patron of art also lends his unique piece of a walking lion, in silver, made in 1865 for a racing prize, and a plaster-proof of the little medallion of "Milo of Crotona attacked by a Lion," executed by Barye in 1819 for the Prix de Rome competition at the École des Beaux-Arts. This little gem, worthy of the antique, did not secure the prize, however, which went to a now-forgotten sculptor named Vatinelle. It had often been so before, it has often been so since down to our day (Comerre was preferred to Bastien Lepage in 1875) and doubtless it will be so for who knows how many years to come.
All the phases of that terrific struggle for existence where beast hunts beast, which have been depicted by Barye's genius, are here. Here is the "Tiger devouring a Crocodile" (with which Barye made his first appearance at the _Salon_, in 1831); the "Jaguar devouring a Hare"; the "Lion devouring a Doe," the "Crocodile devouring an Antelope," the "Python swallowing a Doe," the "Tiger devouring a Gazelle," the "Bear on a tree devouring an Owl" and the "Lion devouring a Boar." What a series of banquets on blood and warm, almost living flesh is here presented! How cruel these creatures are to each other, is the thought that first comes to us, but a second, reminds that it is but their instinct and a necessity of natural law, and repulsion is lost in astonishment and delight at the marvellous fidelity with which the sculptor has rendered these links in the great chain of animal life. Their (as we call it) savage eagerness, their almost blind rage for their appointed food, the tenacity with which they clutch and the ravening _anxiety_ (caused by the dread of losing their prey) with which they tear the flesh of their victims, is portrayed to the life. We speak of a death-grip, but here is a death and life grip--death to the victim whose palpitating body furnishes life to its destroyer. It is the hot-cold-bloodedness of nature, the disregard for suffering of the tornado, the earthquake and the avalanche shown in little in the fangs and claws of these wild creatures. Then there are the battles of the more evenly-matched animals--not always as a result of the need of sustenance--such are the tiger transfixed by the elephant; the python's folds crushing the crocodile; and the bear dragging the bull to earth, or itself, in turn, overthrown by mastiffs. Then comes those groups into which man enters--the African horseman surprised by a great serpent whose formidable folds already enclose his struggling body; the Arabs killing a lion; and the "Theseus overcoming the Minotaur," wherein the calmly irresistible hero is about to bury his keen, short sword in the bull-neck of the gross monster. The success with which Barye has combined the human and bestial characteristics of the minotaur is most remarkable and a similar triumph is won in the hippogriff--the winged horse, with forefeet of claws and beaked nose, which leaps so swiftly over the coiled-shape of the dolphin-serpent, which serves for his pedestal--bearing upon his back the charming, nude figure of Angelica held in the mail-clad arms of Ariosto's hero. To this category _seems_ to belong the "Ape riding a Gnu," the forms, however, being true to nature though appearing fantastic when placed in juxtaposition.
The horse as we know him, and carrying more familiar burdens, is shown in numerous equestrian statuettes, the best of which is the slender, nervous figure of Bonaparte as First Consul, mounted on a proudly-stepping Arab. There is another one of Napoleon, showing him at a later period of his life, and the other equestrian portraits include one of the Duke of Orleans, who looks every inch a gentleman; one of Gaston de Foix, the hero of Ravenna; and one of Charles VII. Then there is a spirited statuette of a Tartar warrior in chain armor sharply pulling back his steed, and a graceful figure of a lady wearing the riding-dress of 1830. A painful contrast is presented by the doomed horse unwillingly carrying a lion whose dreadful grip his frantic rearing cannot loosen. In addition there are many studies of horses, various in breed and attitude, and the small wax model of a young man mastering a horse which though but a rough "first sketch" has all the "go and fire" possible. It would have been of interest if some illustration of Barye's equestrian monument of Napoleon at Ajaccio could have been shown, and this reminds me that except a photograph of the Château d'Eau at Marseilles, showing the four groups of animals designed by him (which Mr. Cyrus J. Lawrence was thoughtful enough to send), and the two reclining river-gods from the Louvre (sent by Mr. Walters), there is nothing which gives any idea of Barye's public work. Not even photographs of the War, Order, Glory and Peace groups of the Louvre, which could have easily been taken from the copies given by Mr. Walters to Baltimore, now on Mount Vernon Place, are present. But, in face of the admirable collection here gathered together, this may savor of ingratitude, and I will return to the consideration of the remaining sculptures.
Among them are some masterly pieces of decoration, the most important being the superb candelabra made for the Duc de Montpensier. These have seated at their base nude figures of the three chief goddesses of classic mythology, whose noble proportions and purity of outline prove the versatility and completeness of the sculptor's art. Juno is accompanied by her peacock and bears the rod of power; Minerva lifts a sword, and Venus holds the golden apple. The candelabra are further enriched with masks and chimeras, and bear at their top a charming circular group of the three graces, small undraped figures, with arms entwined and faces turned toward each other. The general design and exquisite detail of this work is worthy of the Renaissance. There are some more candlesticks and other works of decorative art, all of which bear the marks of a master-hand.
The humorous side of things is presented by some of the groups: in the ungainly figure of the elephant of Senegal running; in the bear lying on his back in a trough and eating with great gusto some sweet morsel which he holds between his paws; and in the meditative stork standing on the back of a turtle. Some of the animals are shown as sleeping or reclining, and there is a cat sitting, a goat feeding, a deer scratching its side and a pheasant walking, among others, but the tragic note is struck in most of them. Probably the best works are to be found among those pieces representing members of the feline race, which were always the subject of Barye's most thorough study. The sculptures of horses are also very numerous, and it strikes one at first as curious that, after all the rebuffs he received from the academic faction, who recognized no animals but the horse and lion as worthy of representation in sculpture, he should have modelled so many of these very creatures. But, after all, Barye's lions and horses belong to an entirely different race from those which the tradition-bound old fogies were pleased with. The collection embraces many admirable bronzes of birds: an eagle holding a dead heron; an owl with a rat; a paroquet on a tree, and a strikingly fine composition of a hawk killing a heron; and there are some beautiful studies of dogs, especially a large seated greyhound, belonging to Mr. Walters. There are rabbits, badgers, wolves and camels, but I remember no cows or pigs, and only one group of sheep. Wild life, much more than domestic, touched the sympathies of Barye.