_ Fer. 16, 1872. | 3 | “S000 a__@_mq_060600 0 0 es, avoidance of angles, intricacy or smallness of parts; equilibrium or mechanical balance of our materials, so as to arrange them to the best advantage—as in roofs, trusses, floors, arches, vaults, &c. Then, concurrently with these laws, there are the properties and qualities of the materials themselves, that, after weight and mechanical considerations, must determine in which place and position each should be used to insure the greatest durability. GaHaG. ‘ (To be continued.) ——E HOW TO BUILD SCIENTIFICALLY WITH THE AID OF MODERN IN- VENTIONS.—IV. WALLS, * TONE.—I have no intention of entering into an elaborate discussion or disquisi- sition on this most extensive subject. I in- tend only to summarise the latest opinions and facts. To those who wish to go more minutely into the subject I would commend the elaborate report made on the occasion of selecting the stone with which the Houses of Parliament are built. I need only add, to show how fallacious such elaborate and ex- pensive reports may be, that (as is so well known) before the completion of those works, so ill-adapted to London was the stone recommended, that decay had commenced and stone-preserving processes been applied. Surely a greater condemnation cannot be ex- pressed, and yet the report is a valuable addition to our knowledge, and was prepared by men of eminence, and with great expen- diture of time and money. The qualities requisite, to quote our old friend Gwilt, for a building stone, are hard- ness, tenacity, and compactness; and he goes on to say that “itis not the hardest stone which has always the greatest tenacity or toughness; for limestone, though much softer, is not so easily broken as glass.” The Decay and Destruction of stone are de- composition and disintegration; the former effecting a chemical change in the stone itself, the latter a mechanical divisionand separation of the parts. Of course the atmosphere in towns and populous places accelerates decom- position. It would be unfair to those who advocate stone, and contend that it will not decay, did I not give their view, which is thus expressed :—‘ Stone is as good at the present day as years ago; that while buildings of long standing show little or no symptoms of decay, many of the modern ones show rapid Symptoms. The cause is not far to seek. There is little or no selection. No seasoning of stone, and many are placed in the buildings ‘ bed out.’ ” Make judicious selection of stone, season it, work it well, and place it on its natural bed, and we may laugh at decay. The two grand divisions of stone are the sandstone and the limestone. The most recent experience will, I think, place sand- Stones on the vantage ground; hereafter I will explain the reason of this. First, it will be necessary to give the lead- ing qualities of a few of the principal stones used in building, and then to draw deduc- tions of the value of the various kinds of building stones in use, reserving the compar- ing of this material with others to another chapter. SANDsTONES.—These are virtually inde- structible, their decomposition can only be effected according to the nature of the cementing substances. It is most important that all these stones should be placed on their natural bed, because from their formation they are generally lami- nated; if, therefore, they are not so placed they will decompose in flakes (naturally according to the thickness of the lamin),
s In this series it was intended that each article should contain one or more subjects complete in themselves, but the subject of stone is so extensive, it is found (with every desire to condense as much as possible) that it must extend beyond the limits we can allow, and will therefore be concluded next week,—Ep, B. N.
THE BUILDING NEWS. 127
and will give a very unslightly appearance to the building, whereas, if placed on their proper (orquarry) bed, the amount of decom- position will be most immaterial. Those of this class most generally in use are Cragleigh, which stands London atmosphere well. (This is a Scottish stone, and I may men- tion that at the demolition of Blackfriars- bridge some of this stone was found in a good state of preservation.) Tisbury is used in London, having been in- troduced about nine yearsago. The cost may prevent its generalintroduction—viz., 10d. per foot at the quarry. There are two beds, but only the hard bed should be used for external work, the soft bed not being capable of with- standing the weather. Mansjield Stone.—Little used in London on account of the expense. There are two quarries, the reddish-brown and yellowish- white. The price is 3s. per foot cube in London, and the expense of working it is at least equal to that of Portland stone. Park Spring—TVhis Yorkshire stone is 1s. per foot cube at quarry; cost in London, 2s. 7d. Colour light ferruginous brown. This stone is well adapted for steps and landings. Forest of Dean.—This stone is principally used for engineering works. The silver-grey bed is fit only for landings and paving. Price 11d. per foot cube at quarry. Limestones, unlike the former class, are less liable to lamination, still it is considered a wise precaution to require that the builder should place them on their natural bed, for the reason that some are shelly, as it is called. The objection to all the limestone series is that the atmosphere has a chemical action on the entire stone, while its action is limited on the sandstone to the cementing substance, and the action, therefore, is limited because, if laid on proper bed, the substance exposed is very small. The objection to all stone of this class is well expressed thus in the report to which I have alluded :— “The mechanical action due to atmospheric causes occasions either a removal or a disruption of the exposed particles, the former by means of powerful winds and driving rains, and the latier by the congelation of water forced into or absorbed by the external portions of the stone. These effects are reciprocal, chemical action rendering the stone liable to be more easily affected by mechanical action, which latter, by constantly presenting new surfaces, accelerates the disintegrating effects of the former.” Those of this class most generally in use are Chilmark.—The good qualities of this stone are warmth of colour, great durability, and a capacity for absorbing very little water. This stone, in the report alluded to, was strongly recommended, but was finally decided against because of the expense of transit. Since that time railway communication has been made with the district, thus altering the cost of carriage. It has been used by Mr. G. G. Scott in the restoration of the Chapter House at Westminster. Bath and Caen—These stones are now seldom used for external purposes on account of their rapid decay. The ‘‘ Box Ground” or the ‘Combe Down” are the most durable; they can be freely worked. The “ Box Ground” is coarser and harder than any of the Bath stones, and it is stated that while most sorts go to pieces in frosty weather this will withstand frost. It is im- portant to know how to determine the proper bed of the stone. It may be determined by the thin black veins which run up the bed; they neyer run in the bed, and insome of the stones there are hard black veins, lists, or ribs; these always run in the bed and never across. The Corsham Down is a good stone for in- ternal work; it has a very fine texture and is of a good warm colour. _ Portland —The Whitbed is the stone known in London as Brown Portland, from its darker colour. It is not so fine in tex-
ture as the base bed, and is liable to have rather unsightly cavities in it, which have to be stopped when the stonework is cleaned down. Rather more costly to work, but stands weather well, if carefully selected. This stone is used for the Holborn Valley Viaduct, the new Grosvenor mansions, and the new Foreign Office. Some contend that the base bed, from its inferiority, should only be used for inside work. It may be mentioned that the quarries from which §. Paul’s Cathedral and many other churches are built in London are closed, the reason being stated that there is no de- mand for the stone by builders, on account of the expense of working it. It should be remembered, where the beds contain flint, or are met with, below layers of flint, that the stone is inferior and will nof stand the weather. The most durable stone has its cementing matter in a solid, a half crystalline state. In the least durable stone it is in an earthy and powdery state. Doulting Freestone.—This is a stone coming more into use, and presents certain advan- tages, one of which is its warmth of colour. Cost.—7d. a foot cube at the quarry. Price in London (Paddington), 1s. 2d. Cost of sawing, 2d. per foot, in London, which is the os same price as that charged for Corsham stone. Notr.—I think a hint to stone merchants good: the proprietor of this stone has issued a price current which, besides giving all the information respecting analyses of his stone, adds the price of it delivered in every county in England. Ancaster.—This is the stone which has been used at the 8. Pancras Railway Station, and to which the preserving processes have been already applied. Price 10d. per foot cube at Ancaster Station. Kentish Rag comes under this class, and its peculiar advantages and character are so well known as not to need further mention. Painswick is a close, white-grained stone, finer than Corsham Down; but it is harder, and consequently more expensive to work. Used much for the same purpose. Price in carts at Paddington Station, 1s. 6d. per foot cube. Comparison between Sandstones and Limestones. —It would appear, then, that the limestones, generally, may be said to have the advantage in expense. Roughly, it may be taken that the cost is from one-fourth to one-third cheaper in the material, and the labour about 20 per cent. cheaper. On the other hand the sandstone would appear to be the more enduring stone. B. F. —_>—_—_. DIAPER BRICKS. as “‘streaky-bacon style,” as it was ir- reverently called, seems to have had its day; it is passing from the hands of archi- tects into those of builders andabandoning the church for the suburban villa. It is natural enough that men of taste should be disgusted at the abuse of the system, and should reject a style of ornament that has suffered such degradation. The result is unfortunate; colour may be used to good purpose in brick- | work as in everything else, and it is a pity that we should be debarred from its employ- ment because vulgar people have introduced it in a vulgar way. What has thus happened with coloured bricks is exactly what is now happening with diaper bricks. They are having their day, and so haying it that it is likely to be a very short one. They, too, might find a place in architecture; but we doubtif they willlive toattainit. Weshallhaye a surfeit of them, as we had of the red and black ones, and sicken at the sight for ever after. It would not be too much to say that some of us have sickened at them already. When we see the front of ashop covered with surface decoration from Westminster Abbey, and the side of a gin-palace with diaper from Chartres Cathedral; when houses, and even cottages, are plated from plinth to parapet
