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Over 350,000 rivets (each of which was required to be made red hot before they were driven home in their respective places) were used to connect together the above-described 1778 tons of iron. The cost of the iron bridge superstructure proper was $435,000. The total cost, including additional masonry, temporary sup port of tracks, and other incidental expenses, $530,000. The iron, of a superior quality, has been purchased for the whole structure, from Messrs. J ones and Laughlin, of the Ame rican Iron Works of this city. The principle of the construction is known as the latticed- girder plan with vertical stiffenings, and the structure is believed to be the only one of the kind in the United States, although the principle is used very extensively in modified forms on the German, Russian, and Italian railways.—Journal of the Franklin Institute CONCRETE AS A MATERIAL FOR HOUSE AND WALL CONSTRUCTION. In December last a Paper was read before the Architectural Asso ciation by Mr. Tall, the patentee for Apparatus for the Construction of Concrete Walls, &c., upon “ Concrete as a Material for House and Wall Construction.”* A special meeting of the Association was subse quently held for the purpose of discussing the subject. The discussion was opened by Mr. J. D. Mathews. Mr. Mathews said that the meeting had not to discuss the material (concrete) itself—but rather the adaptability of that material fo the construction of dwelling houses and like buildings. Everybody knew that concrete was a material of extreme durability, which had been used from the earliest times. At the Abbey of Reading, for example, it had been used with facings of stone ; the lapse of time had made a ruin of the stone work, but the concrete core remained intact. This proved conclusively that the material could stand for any amount of time. Modern instances of the successful application of concrete might be seen at Dover Harbour and the Brighton Breakwater. From such examples as these and the many experiments made of the strength and durability of the material might be taken for granted. As regards the application of concrete for building purposes, various methods had been tried from time to time. It had been endeavoured to build with concrete blocks in the same manner as with blocks of stone. This was a very good contrivance, but it did not seem to satisfy the requirements of the case, inasmuch as it required a great deal of labour. The blocks had to be made in the first instance, scaffolding had to be erected, and the blocks set like ordinary stones. There was also the plan of run ning concrete between an internal and external casing of brick, and by this means form a wall impervious to the weather. This was in itself a very good plan, but unfortunately caused three times the labour than an ordinary nine-inch wall, and a corresponding increase of expense. A third plan was that of making temporary trenches with boards and filling in the concrete. This was, however, an imperfect method, as no dependance could be placed on its giving straight walls. A fourth method was by means of hexagonal tiles of ordinary earthen ware, made hollow, set on end, and filled in with concrete four or five inches thick. This might be a very good plan but seemed too intri cate for general use. The gentleman who had invented this plan was apparently afraid of the concrete as a structural material, and so had adopted this method of building with tiles. In using them, it would however be necessary to resort to iron ties, bolts, &c., and the system was altogether too intricate to come into universal practice. From this variety of methods, however, one thing was obvious, namely that concrete could be used, provided the proper method were adopted. ■Whatever the method might be which should ultimately succeed, it was necessary that it should be unequivocally practical and advanta geous. People were usually prejudiced against new materials, and this prejudice could only be overcome by any method to be introduced being of unquestionable benefit. The special subject now to be con sidered was Mr. Tail’s system. That gentleman asserted that his system was the cheapest which could be had. If so Mr. Tall has es tablished his apparatus as the means, the only means for the successful application of concrete. With regard to his apparatus uMLing could be simpler. The chief thing necessary seemed to be to get the founda- dation perfectly level, and the rest of the building would of necessity be carried up truly vertical. A proper foundation was essential for any building, but was more necessary for a concrete building, than for any other. He wished to know what would be the effect of the settling of the foundation of a concrete building. The wall of such a building would be too solid for displacement, although it was obvious that something must give way. Might not the failure of the concrete dwellings at Beckley be owing to some such cause ? The one great difficulty however seemed to be in the proper mixing and filling in of the concrete. Everything depended * See “ Civil Engineer and Architect’s Journal ’’ for December, 1S67, page 343. upon the workmen mixing with correct proportions. If they, through ignorance or carelessness, did not do so, the probability was that failure would ensue. Workmen took every possible means to do those things which they ought not to do, and to leave undone those things which they ought to do. So great was the importance of this, that unless there was some guarantee that tho materials would be mixed properly, it was questionable how far the plan could command extensive adoption, and to obviate these objections implied increased cost. He desired also to know if Mr. Tall had ever found that the concrete dried too rapidly to allow of the plaster being properly applied. He thought that Mr. Tail’s method of making circular flues and of conducting bell wires or speaking tubes worthy of praise, but he did not think that the rain water pipes should be formed by grooves in the concrete. In the event of tho pipe being stopped up it would be difficult to clear, while the cost of zinc or tin pipes was so trifling, that it would not be worth while to adopt such a plan. Concrete floors had the advantage of keeping out rats and mice from the dwelling, and at the same time he considered would make the rooms warmer. The plan which he believed Mr. Blomfield intends adopting was exceedingly good, viz.:—to furnish the concrete floor with acoating of Portland cement, and to fix a wood fillet, wood all round the room on which to nail the carpets. A concrete floor was especially desirable on the basement, as the joists were generally so near the ground as to be especially liable to damp, and consequent decay, but by the use of concrete not only would this be obviated, but at least a foot would be saved in the height of the building. Concrete roofs on the other hand he did not think it advantageous to use. They were especially liable to be attacked by frost and could not therefore be depended on, unless they were coated with asphalte, the cost of which would considerably exceed that of slate. The last point he desired to mention was the artistic treatment of the material. It was the most important, and at the same time, most difficult subject. It was very certain, however, that the architects of the present ago would never allow themselves to be beaten by any new material. They would be able to adapt design to its use. In this construction all ornament should be applied. He could not agree with those who would leave the concrete as it was filled in the mould or trench; the house would look very barren and bare without some applied ornament. He would therefore suggest that the front should be divided into squares or other geometrical forms and filled in with ornamental plaster or pargetting, similar to that to be found in many old timber houses existing in old cities and towns. Encaustic tiles might very well bo made use of in similar decoration. They had many of them seen some of the old timber framed houses at Beauvais, one especially he remembered, tho upper part of which had the interstices between the wood frames, filled in with tiles and orna mental brickwork, producing a very pleasing effect. Both plaster and tiles were manufactured materials; lie thought they could be used together very humourously and truthfully. If applied ornament were objected to, he could suggest terra cotta, which, if mace in blocks, and set in trenches, or moulds, as the work was carried up, might be used very effectively. He did not think a concrete building could with propriety be faced with brick; it would be deceitful to do so, ho would much rather see the building covered with cement, as in the brick faced building there was nothing to shew that the inside was not of the same material as the outside, whereas the cement was really one of the materials used in the construction of the walls. On tho same principle he greatly objected to concrete being moulded into the form of an arch. The lintal was the proper form for door and window heads in concrete, as there could be no more strength in an arched mould than in a straight one. All things considered, he thought concrete a useful addition to building materials, and although not likely to supersede brick and stone constructions, he should have no hesitation in making use of it should occasion offer. Mr. Blashill said he had taken considerable interest "in this new material. From what he had seen of it it seemed to be a perfectly feasible method. There were ’only three or four materials used in building—wood, stone, brick, and of late iron. Concrete would simply take the position of being the fifth in the field. In some parts of the country the first named materials would be the cheapest, in others con crete would be cheapest. It was absurd to suppose that concrete would in every locality be the sole material for building. In a stone country stone was the appropriate material, in a wood country, wood ; in a clay country, brick; and in a gravel country, concrete would be most gene rally in use. He was pleased with the ingenious apparatus which Mr. Tall had constructed. At the same time it seemed as if it would result in a stereotyped dwelling house, as it was necessary to have every room exactly at the form provided by the apparatus. This was a dis advantage from which stone and brick were free, and if Mr. Tall could provide for such variations it would vastly increase the utility of his invention. Mr. Tall had published a statement of the advantages of concrete over other materials. The first was that it was half the cost of construction in bricks and mortar. Mr. Tall had given no figures to prove this assertion, and he (Mr. Blashill) was satisfied that it could not be done. He thought such sweeping assertions did more harm than good to a new invention. Though there might be some places where it could be done, there were many other places where it could not. The next advantage claimed for concrete was that it had ten
