Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/114

 98 THE BUILDING NEWS. Fes. 2, 1872. was sorry to say, far too much matter and too little spirit. Much of this was, he felt sure, due to the want of a higher training for artists. With regard to the Mexican mounds, he had himself, when in Treland, had occasion to notice the great resemblance they bore to the Irish cromlechs. It was announced that the next lecture would be on “ Light and Colour,” and would be delivered by W. Spottiswoode, Esq., M.A., F.R.S. The hall was crowded, many persons haying been unable to find accommodation. The session bids fair, therefore, to prove asuccessful one for the society. ——_»———_ DECAY IN STONE: ITS CAUSES AND PREVENTION.* CANNOT conceive that there isa class of sub- ject of more importance to us as young profes- sional men, and more deserving of our diligent study, than that which treats of the properties and constituent parts of various building materials, not so much with regard to their action under various weights and strains incidental to the position assigned to them, but to the general effects produced by time and other influences. It may be suggested that this knowledge can only be acquired by years of labour and patient research, and that by making us chemis‘s and mineralogists, it would divert one’s thoughts from our legitimate pursuits as architects orengineers; but while in the abstract this may be true, it can hardly be considered as an argument in favour of the general neglect of these subjects by pro- fessional men, as is evidenced by numberless failures, We, as a society, have always recognised the im- portance of these subjects, as every session they have been more or-less prominently before us. The pre- servation of timber has been ably handled by Mr. Bancroft; the corrosion and deterioration of iron by Mr. Dawson; the preservation of iron is to come before us later on in this session; and the subject before us to-night has been dis- cussed, not only by the President (Mr. A. C. Pain), who, however, may be said to have made it peculiarly his own, but by other members. The subject is in some respects familiar to me, as seven or eight years ago I introduced it to the society ; since then its importance has become more apparent, and my interest in it has correspondingly increased. This paper is intended as a supplement to the President's on the use and selection of stone, which was brought before us last year; and it may be well to give abrief réswmé of Mr. Pain’s address} so that we may the more readily take up the subject where he left it. The leading points in that paper were something as follows: —First, a carefully-prepared table, giving full particulars of each building stonein use in London, its mineral and geological designation, its component parts, chemical analysis, and colour, also weight per foot cube, average size of blocks, suitability of various beds for different purposes, manner of working same, cost per foot cube at the quarry and in London, and names of principal buildings, ancient and modern, in which each has been used. This table is evidently the result of great care and trouble, and cannot fail to be of much practical value to all who are interested in the subject; it may be remembered that Mr. Pain kindly promised to allow ary gentleman to take a copy of it. Then followed a detailed account of these stones, taken chronologically as they came into use, which comprised the bulk of the paper. Next came some general remarks on the question of decay, which the author attributed mainly to want of proper selection, and to the ignorance of the material with which they were dealing on the part of the architect, engineer, working mason, or clerk of the works ; and finally came the suggestion of the appointment of a royal commission to collect specimens from every quarry in the kingdom, to be placed in the museums of al] the large towns, to subject the same to chemical and mechanical tests, and to report from time to time the results of their labours. The interesting dis- cussion which followed turned principally on the subject of decay, and we were favoured with the remarks of several gentlemen of prac- tical experience, which, though they did not solve the question before us, were still of much value to us. And now let me attempt to take up the question of decay in stone, its cause and prevention, where Mr. Pain left it, omitting as he did, and for the same reason, any reference to granites. Building stones may, generally speaking, be divided into two classes—viz., limestones and sandstones. Limestones are composed of carbonate of lime, or the carbonates of lime and magnesia, either nearly pure, or mixed Society, January 19th, 1872, by Mr. JAmEs B. WALTON, Assoc. Inst. C.E. ee page 403, BUILDING News, No. 855, Vol. XX. with variable proportions of foreign matter. Their decomposition depends upon the mode in which their component parts are aggregated. The various kinds of limestones termed oolites being composed of oviform bodies, cemented by cal- eareous matters of a varied character, will, of necessity, suffer unequal decomposition, unless such oviform bodies and the cement be equally coherent and the same chemical composition. The limestones, which are termed “shelly,” from beizg formed of either broken or perfect fossil shells, cemented by cal- careous matter, suffer decomposition in an unequal manner in consequence of the shells, which being for the most part crystalline, offer the greatest amount of resistance to the decomposing effects of the at- mosphere. Sandstones, usually employed for building purposes, are composed of either quartz or siliceous grains, or siliceous grains cemented by siliceous, argillaceous, calcareous, or other matter. Their decomposition is effected according to the nature of the cementing substance, the grain being practically indestructible. Sandstones, from the mode of their formation, are very frequently laminated. Hence, if this stone be placed in buildings with planes of lami- nation in a vertical position, it will decompose in flakes; whereas if it is placed so that these planes be horizontal—that is most commonly on its natural bed—the amount of decomposition will be com- paratively immaterial. Limestones are not liable to this kind of lamination; nevertheless some varieties exist, especially those called “‘ shelly,” which have a coarse laminated structure, generally parallel to the plane of their beds. Therefore, some precaution in placing such stone in buildings, so that the planes of lamination be horizontal, is as neces- sary a5 with the sandstones above noticed. With regard to the Houses of Parliament, which are built of a magnesian limestone or dolomite, it does not appear that the decay is attributable, as is com- monly supposed, to the stones not being placed upon their natural bed, or in the same relative position they occupied in the quarry, as stones which were found horizontally in the quarry were often placed perpendicularly in the building, and used for pur- poses of the most delicate ornamentation, without any injurious result. It does not appear that it is all possible to account for the lamentable state of decay into which this stonework is falling on any other ground than that which has been before so frequently advanced—viz., the want of proper care in the selec- tion of the stone at the quarries. You will remember that it was to this cause that Mr. Pain attributed generally the decay of stonework. In the special case of the Houses of Parliament it was shown un- mistakeably that no proper oversight was exercised at the quarries, that good and bad stone was used indiscriminately,although one of the original commis- sioners, who was a man of great experience, actually volunteered for a nominal salary to take upon him- self this special work. A very superficial examina- tion of this» building will satisfy any impartial observer that the character of the stonework is unequal, as while it cannot be denied in many cases that the effects of damp and exposure have accelerated the progress of decay, in other instances very rapid deterioration is taking place where these causes are altogether in- operative, and further, it will be remarked, which is a most important point for our con- sideration, that in many cases in the same stone the work of decay is by no means general, but is confined to a space which might often be covered by a square inch or so, Chemical analysis fails to help us, because, after most elaborate inquiries, the chemists can only tell us that they fail to detect any chemical difference in the sound and decaying portions of the stone; the cause of decay in stones which are chemically similar must to a great extent be attri- buted to the mechanical manner in which the particles are aggregated, or in other words, to the unequal physical structure; in proof of this, the chemist on the Commission appointed in 1861 to in- quire into the cause of the decay of the stonework in the Houses of Parliament, gave the following as some of many instances which might be cited :— “Marble and chalk are chemically identical, but, owing to their physical structure, the one being crystalline and the other amorphous, the former is less acted upon by acids than the latter. Again, peroxide of iron is readily soluble in acids, peroxide of iron in the form of hematite is attacked with difficulty by acid, and the same oxide, after ex- posure to powerful heat, is almost entirely insoluble in acids.” To revert to the opinion expressed with reference to the selection, or rather the non-selec- tions of the stone as being the principal cause of decay, it would appear, in the case of the Houses of Parliament at least, to be satisfactorily established, and doubtless what is true here would be equally so in numberless cases besides. The peculiar compo- sition of the London atmosphere would stimulate decay when once it became apparent, though it would not in itself afford any satisfactory argu- ment for it, because if so its action ought to be general. The report of the sub-committee of the Commission to which I have already alluded appointed to examine the buildings in the metro- polis constructed with stone similar to that used in tne Houses of Parliament, is in itself an additional corroboration of the statement, because while in many instances where no judicious selection of the stone was made rapid decay is apparent, in others, and notably in the case of the Museum of Economic Geology, in Jermyn-street, where Sir Henry de ia Beche paid great attention to the selection, the stonework is, generally speaking, intact. You will remember the remarks which were made at the close of Mr. Pain’s paper by Mr. Cross, who is superintending the stonework of the Prince Consort memorial, Mr. Cross is a man of many years’ experience, and supplements his experience by a considerable amount of shrewdness. He attri- buted the decay of stonework in the metropolis entirely to the want of proper selection. Dismissing altogether the effects of the London atmosphere, about which in many quarters we hear so much, he tells us that he has removed the accumulated soot from the face of stone, and on examination found the stone quite sound and perfect. It will be well for us now to consider a little more closely the question of atmospheric influence in London, as, though Mr. Cross’s opinions may claim our best attention, on this point at least they are neither explicit nor con- vincing, because it is, I believe, generally admitted that atmospheric causes enter largely into this ques- tion, especially in London. The experienced chemists to whom I have already referred give us the ‘‘ nature of the changes to which building stones generally are subject under atmospheric influences.” Under normal” conditions these changes must be ascribed to the action of the oxygen, carbonic acid, nitrie acid, and water in the atmosphere. In the air of towns, how- ever, there are certain other constituents, such as several acids of sulphur, and occasionally hydro- chloric acid, which cannot fail to exert an additional disintegrating influence upon building stones. They tell us that the air of Manchester, according to Dr. Angus Smith, contains an average proportion corresponding to one part of sulphuric acid in every 100,000 parts of air, which, in the centre of the town, rises to 25 parts in every 100,000. No data exists with regard to the proportion of sulphuric acid in the London atmosphere, but they are assumed to be equal to the average of the amount found in the Manchester air; they must therefore be regarded as among the more important agents destructive to stone. (To be concluded next week.) os BOOKS RECEIVED. Text-Books of Science (Longmans, Green, & Co.): Theory of Heat, by J. Clark Maxwell, M.A., &e., is the last published of the useful text-books now being issued by Messrs. Longmans, and well sustains the promise of its predecessors. The author’s design is to show the scientific connection of the various steps by which our knowledge of heat phenomena has been extended. This he does with as few mathematical formule as possible, thus bringing the work within the range of the average student. How to Publish a Book, d&c., by Ernest Spon (London: E. & F. N. Spon), contains detailed instructions to intending authors how best to usher their compositions into the world of printing and binding. The Civil Engineer's Pocket-Book, by J. ©. Trantwine (Phila: Claxton, Remsent, & Haffel- finger ; London: Triibner & Co.), will be found of great use, especially by the younger members of the profession. ‘The author’s very laudable object has been to elucidate in plain English important but ele- mentary principles, which, as he truly says, “ the savans have enveloped in such a haze of mystery as to render pursuit hopeless to any but a confirmed mathematician.” The pocket-book contains over 630 pages of small type, and is full of useful matter. The Perpetual Cross Calendar, by C. J. Recorden, B.A, (London: Triibner & Co.), is what its name indicates. Drawing for Stonemasons, and Gothic Stonework, by Ellis A Davidson (London : Cassell, Petter & Galpin), are the last published volumes of Jassell’s Technical Manuals. The City of London Directory, 1872 (W. H. Collingridge, City Press Office), is well got up and well printed and bound. It gives a large amount of information, not usually found in a directory, connected with the City of London, and which could not be so well imparted by any one as by the publishers. Many other excellences that might be mentioned deepen
 * Paper read before the Civil and Mechanical Engineers