Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/164

 148 THE BUILDING NEWS. Fez. 23, 1872. uniformly mingled together as possible. He says it is only in the darker stones that the colouring matter has any tendency to disinte- grate the mass. He contends one sample is not enough to test a quarry by, but that the rock or place should be examined at the out- set, and then he states his reasons, which I am tempted to give, because from them we gather the American view of this subject, and also, because the value of this report in that country is somewhat equivalent in importance to that of our own Commission to which I have alluded. “For in its natural outcrops it has been exposed to the action of the weather, in all its influences, for many thousands of years. One of the principles taught in elementary geology is that the soft and decomposing rocks appear in low rounded or flattened exposures, or entirely covered by the soil of their own débris, forming no conspicuous feature in the country ; while, on the contrary, the harder rocks stand out in relief, producing marked and distin- guishing features in the landscape. It not unfre- quently happens that the geologist, having familia- rised himself with the succession and character of the rocks of a particular locality or neighbourhood by seizing the features and character of the promi- nent beds, is able to trace them in succession along the escarpment or mountain range as far as the eye ean reach, and to approach them from any distant point with assurance that he has not been deceived. “The strata which make these features in the land- scape are the eyer-enduring rocks, which haye with- stood the action of the atmosphere through a period a thousand times longer than any structure of human origin. One cannot doubt that, if properly placed in any artificial structure, they would still withstand the action of the elements. ‘These escarpments, in their natural situation, may be coarse, rough, and forbidding, more or less dilapidated, or unequally dilapidated from the effects of time; but as they there present themselves, we shall be able to see their future in any structure exposed to the same influences. “Tt is true, however, that no artificial structure or position will ever subject the stone to the same degree of weathering influence to which it is exposed in its natural position, but the same changes in degree will superyene upon any freshly-exposed surfaces. In its natural position the bed has been encased in ice, washed by currents, saturated with rains and melting snows, frozen and thawed, and ex- posed to the extreme of summer heat without miti- gation. The rock which has withstood these in- fluences is quite equal to withstand the exposures of a few centuries in an artificial structure. Yet there are occasionally modifying influences and conditions which have sometimes subdued the permanence of a durable stone, and given preference to others less durable. It,therefore,becomes necessary to carefully examine all these conditions, and to determine, not only from the rock in place, but also from its physi- cal constitution, whether it will meet the require- ments of the structures proposed. “Tt not unfrequently happens, in working a quarry, that layers are reached which have not been ex- posed to the weather, and it is then necessary to test the strength and power of endurance of the stone. This may be done by repeated exposure to freezing and thawing, by testing the strength or power of resisting the action of the weather, but» will deter- mine also whether such foreign ingredients as iron pyrites may exist in the mass. “ Chemical analysis may be resorted to for the pur- pose of comparison with specimens of known com- position and durability ; but chemical analysis alone cannot determine, without other testing experiments, the strength or power of endurance of the stone.” Old Buildings are somewhat of a test, but only to a limited extent, as sometimes the stones of which they are built were brought from a distance, or the particular quarry has been worked out. Should the old building show decay, it may arise from the stones not having been well selected, or they came from those beds first worked at the opening of the quarry, and may not be so good as those which the quarry now produces. The difficulty of obtaining a genuine test of a stone is great, because each quarry owner who desires a chemical test is more ‘likely than not to take the sample from the best bed of his quarry, and obtain the analysis on that, and thus he has a certificate of quality which applies to the entire quarry, while, in reality, it may not apply to a twen- tieth part of the stone he sends therefrom. Some have suggested a Royal Commission to visit every quarry, take samples where they like, and test them. Mr. Trickett, who writes on the subject, and is, I think, a stone mer- chant, and therefore must have much expe- rience, suggests that the ‘‘ practical men who have made the subject a study, should give a plain statement of facts,” or ‘the quarrymen themselves give us their views;” he goes on to say, fairly enough, ‘‘these would, no doubt, be to a certain extent one-sided ;” but adds, ‘‘who can speak of the qualities of a stone like those who have worked at it all their lives ?” Advantages.—Appearance. Power of ya- riety of decorative design without increase of expense. Disadvantages.—Decay. Expense. Cost of producing decorative work. The decay and difficulty of selection I have already enlarged upon. As to whether the former can be, by processes, patented or otherwise, prevented, we shall hereafter con- sider. The expense.—This I have placed to each sort of stone. The comparative cost will be considered in the chapter dealing with the relative expense of building with the various materials at our command. The expense with regard to decorative works is that where great quantities of the same thing are required, each one in stone costs, of course, about the same, while in artificial stone or terra-cotta, amouldis made, and thus, the more there is wanted the less is the cost of each one. But the serious point is the damp. In a paper read before the Liverpool Architec- tural Society, the writer, speaking on this point, explains it thus, that the damp which is frequently seen under stone cills in new buildings results from the skin of the stone having been taken off by working the stone, causing the water to find its way through the stone cill to the wall beneath, and gives (as a partial remedy) painting, stating this ‘‘ may often be remedied by giving the top two or three coats of good oil paint.” But I come to the more serious cause of damp inside stone houses, and which is frequently pre- vented by the expensive method of a lining inside of the walls with bricks, This is called— Osmatie Action —No matter what thickness the walls, if built of limestone, they will absorb moisture on the outside from the atmosphere, and give out that which it has absorbed in compliance with the law of osmus, through the action of heat in the interior of the house. The increase of the heat in rooms where walls are built of limestone, instead of drying them in rainy weather, actually has the op- posite effect, for the osmus is superinduced by the attraction of the heat thus created, and the thin surface of fine rain-water, percolating through the stone, becomes thicker, and es- tablishes itself in large globules on the plaster of the inside face of wall. Damp, also, affects all limestones by capillary attraction. ‘This must be guarded against, or damp from the ground will be sure to insinuate itself into the warm rooms by way of the centre of the lime- stone wall, even should the external face of the wall be waterproofed by some process. The capillary attraction may be prevented by a waterproof course between foundations and superstructure. Treatment—According to the grit of the stone must be the decoration. If this be coarse, heavier contours with coarser arrises and fillets. Stone does not possess that even- ness of colour that marble does, but its very differences of tint will, I think, be considered an advantage. Proper effeet in carving is obtained from bold treatment. I quote Sir William Chambers, who sayssotruly: ‘When objects are near and liable to inspection, every part of the ornament should be expressed and well finished ; but when they are much exalted the detail may be slightly touched or entirely neglected; for it is sufficient if the general form be distinct, and the principal masses strongly marked; a few rough strokes from the hand of a skilful master are much more effectual than the most elaborate finishings of an artless imitator, which, seldom consisting in more than smoothing and neatly rounding Damp. off the parts, are calculated to destroy rather than to produce effect.” I do think that much of the work of the present day is too finely finished for the material, and that more effect could be ob- tained with less expenditure; but here I am on debatable ground and would give but one piece of advice. Remember in designing ornament to consider where it is to be placed and endeavour to realise the effect, or where your decorative works are placed in situ dis- appointment awaits you. Preserving Processes—What is required in any process is the protection of the stone against the chemical action of the atmos- phere of our towns, and the mechanical ac- tion of winds, rains, and frost. The aspects which suffer most severely from decay are the south, south-western, and western fronts. As this is generally admitted it only behoves the architect to take especial care that the stone of fronts haying such aspect should be well seasoned and selected; and then, if requisite, haye the preserving pro- cessses most carefully applied. Zs there any process that will do what is required ? I am of opinion that we must wait some time still before we can arrive at a decision on this point and on the comparative merits of the many systems that are before the public. Mr. Ransome’s process is sup- ported by a report of Professor Ansted and many other goodmen. Professor Chureh’s is more modern, the new patent being 1869. There has, therefore, been very little time to test the endurance. ‘The coatings comprise three transparent colourless solutions. It is usual to apply one application a day. In the third coat or application any pigment may be added. The softer the stone the more it absorbs. ‘The cost for sufficient materials to do with the threeapplications, 100 superficial yards, is £2 2s. 6d. The best time for the application of all preserving materials is dry weather, Conclusion.—I must now leaye the subject to preserving stone, as to which there isso much uncertainty, which must continue, [ am afraid, until the question is taken up and thoroughly investigated with the same patient labour that Tredgold and Fairbairn devoted to wood and iron. I can only suggest that we may all derive some little consolation, till that time arrives, by remembering the words of Professor Don- aldson in his opening address at the General Conference of Architects where he says ‘Our Bath oolite is equal to that of Paris, if only our miserable economy in some cases, and the spirit of competition among un- principled contractors, the stone merchants and quarrymen themselves, did not counteract the intention of the architect, and bring into use the stone from inferior beds, instead of from the soundest and best strata. There is not a better stone than our sea-girt Port- land, if only properly selected, whether for its tone, its homogeneousness, or resistance to the atmosphere. $. Paul’s Cathedral, thanks to the precautions of the illustrious Wren, and Somerset House, may be cited to prove the enduring qualities of this material, when carefully chosen in the quarries. In these two buildings the arrises of the mould- ings and angles, and the very carvings, still retain their sharpness.” I have shown how little is really known on these subjects, and how wide a field still presents itself for inquiry to the energetic, painstaking student. 1. To determine which is really the best quarry of each class. , 2. To find whether the sand or limestone is most enduring. . .3. Having discovered the two preceding points, to fix the difference of cost of the best of each kind, so that the architect may be able to place that important item before his client. 4, Assuming, as present practice seems to require (so many new buildings being at oot