During recent years an interesting change has been gradually brought about in the various methods of building construction employed in France, and more especially at Paris, where the size and importance of public buildings and the many-storied houses divided up into flats necessitate special systems of construction, which possess the advantages of combining economy in cost with strength and durability. Parisian architects and builders, although far from approving the extremes to which their American confrères go in the employment of iron for the construction of their somewhat exaggerated sky-scraping buildings, in which the style of architecture employed is often scarcely logical or consistent with the modern methods of construction, are nevertheless obliged to own to the necessity and the utility of employing iron in moderation for the framework of their buildings. Up to the present the use of iron in its ordinary form has chiefly been confined to floors, partitions, and roofs, where, as a rule, its presence is masked by coverings of cement, wood, or stone, except in recent examples of the new style of buildings destined for brasseries or drinking halls, where the iron construction is left visible, and emphasized by means of bronze or color painting and mosaic work, or, again, in the few examples of well known work where the architect has endeavored to obtain a decorative effect by means of iron lintels and columns.

But where the use of iron is fast finding favor at Paris is in its employment in combination with other materials such as cement or concrete, and in a special form known as the cement armé systems, in which iron or steel is employed in the form of thick wire, trellis, or light bars embedded in cement or concrete. This method of construction, of which there are three different systems, has for some time been employed in the construction of various buildings of more or less importance, and has given proof of its strength and practical use as well as its advantages when employed for floors, partitions, walls and roof, both as regards its conveniences for internal arrangements, its economy, and as regards the manner in which it lends itself to modern schemes of polychrome decoration.

Two of these systems have been employed by the architect of the new building now being constructed in the Rue Blanche for the Society of Civil Engineers of France. The third system is much employed by M. De Baudot in various buildings designed by this architect, an advocate of rational construction and design and the logical employment of modern building materials. It will be interesting to examine the merits of each system as employed in these buildings, together with any other points of construction worthy of remark.

The building for the Society of Civil Engineers is remarkable from several points of view as regards construction and the arrangement of plan. The façade and plans will appear in the Building News as soon as the work is completed, and will form an interesting subject for comparison with the building recently completed for the English Society of Engineers, and with that about to be commenced at New York for the American Society.

Before entering into a detailed description of the system employed, a summary idea of the plan and general scheme of construction will not be uninteresting. The architect, M. Fernand Delmas, has endeavored to construct the building on economical lines, employing to a large extent iron and those modern materials which have been tried and found fitting as regards suitability and economy; the building will cost £22,000, and it has been made a sine qua non that all the contractors shall be members of the Society of Engineers.

The length of the façade is 100 ft.; the total depth of the building is nearly equal to the frontage; the height from pavement to cornice is 60 ft. The façade is built of solid stonework throughout its length and height. The thickness of the masonry is 24 in. at the lower stories and 18 in. at the upper portion. The façade wall is really the only portion of solid masonry work in the whole building, and forms a decorative mask to the body of the building, which is constructed of a framework of iron. The chief supports of the building proper consist of four framed iron uprights, 16 in. by 16 in. rising from the basement to the roof. These uprights are solidly trussed and held together at the floor levels by strong iron girders supporting the iron joists of the upper floors and the light partitions which divide up each story. This system is at once economical and practical. The whole building is thus self-supporting, and the thick walls which would otherwise be necessary for carrying the upper floors are thus avoided.

The façade wall is built according to the system always employed at Paris, and is formed of blocks of stone roughly cut at the quarries to the outside dimensions of the proposed moulding and decorative work. As soon as the whole front is erected the work of cutting it into shape will commence, the mouldings, pilasters, and all carving work being done while the interior is being prepared. The buildings at Paris are by this means erected much more rapidly than when the stone is dressed or moulded before being put into place. Greater facilities are thus given for studying the general ensemble of the façade and the proper scale to be given to the mouldings and decoration. The stone is as a rule soft when first from the quarries, but becomes hard and durable after dressing and exposure to the air. The courtyard wall of the building is formed of light brick or metallic fillings between the iron uprights and the party walls.

The ground floor comprises a large entrance hall or vestibule, 40 ft. by 44 ft., forming, with the cloakroom, the principal staircase, the rooms for the concierge, and the area, the whole front of the building. This large vestibule is vaulted over by means of one of the systems of cement armé to be described. The floor is constructed on another similar system, and will be paved with mosaic work. The ground floor of the courtyard will be occupied by the conference hall, 50 ft. by 50 ft., to hold 300 seats. An annex, 50 ft. by 20 ft., adjoining this hall, will open on the same by a large arched bay, and may be separated from the larger hall by means of a special system of wooden soundproof roller shutters. The floor of the large hall will be a movable one, to be raised or lowered by an ingenious system of hydraulics, and capable of being placed in an inclined position for conference meetings, or raised to a horizontal position for ball room purposes.

The entresol floor will comprise a large room for meeting, smoking and conversation rooms, and a reading room, to be used as a club for the members of the society. The first floor will contain the offices of the society, a large committee room, and all conveniences. The second floor will be devoted entirely to the purposes of the important library, comprising the library proper, a room 45 ft. by 25 ft. by 17 ft. high, rising to the ceiling of the low story above, and lighted by a large semicircular bay at either end: the surrounding rooms of the height of the second floor will be destined for the librarian, catalogues, drawing office, and library offices. The third floor will be devoted entirely to the purpose of storing the books of the library, in low rooms communicating by means of the gallery overlooking the library below, which will be crossed by means of a light, iron bridge. The bookcases will be suspended from the upper floor, and will be arranged in vertical tiers hung on rollers, after the system employed at the British Museum. The roof story will be divided up into an apartment for the chief secretary, and reached by a private staircase from the ground floor.

The large basement, occupying the whole of the ground surface of the building, will be used for storing the records of the society, and will contain the heating apparatus, stores, etc. A hydraulic lift will afford access to the landings of each floor. The chief feature of the façade, which is simple in style, is the wide arched bay, 24 ft. across, rising from the pavement to above the cornice; this bay will be filled in with an open decorative framework of wrought and cast iron.

Some of the most interesting points of the construction, besides the large use of iron, are the systems employed in the construction of the floor. The ground floor is built after the Coignet system, composed of light iron bars and cement; the first floor and its supporting pillars and arches is constructed after the Hennebique system of cement armé; the upper floors are formed of iron joists, filled in either with the system of light supports and plaster, much employed at Paris, or with terracotta fillings between joints. The roof is lined internally with agglomerated cork bricks, affording protection from excessive heat or cold, and the walls of the area will be lined with opaline, a vitreous material of a bluish white color, which in this case will insure cleanliness, and afford additional light; the lavatories and water closets will also be lined with the same material.

Speaking of the Hennebique system of cement armé, employed for the arches and floor of the first story, it will be interesting to illustrate the method by a few sketches, explaining the theory of this system, which has been put to practical proofs in a large number of buildings, chiefly for industrial purposes, in the north of France. The perspective section will give an idea of the construction as employed in the building for the civil engineers, a system which holds its ground well against its rivals of other methods of cement armé. - The Building News.