topped out, and the roof tier of beams shall be strongly braced to the beams of the story below until all the floors in the said building are laid.

"SEC. 9. Headers. All stone walls less than twenty-four inches thick shall have at least one header, extending through the walls, in every three feet in height from the bottom of the wall, and in every four feet in length; and if over twenty-four inches in thickness, shall have one header for every six superficial feet on both sides of the wall, and running into the wall at least two feet; all headers shall be at least eighteen inches in width and eight inches in thickness, and shall consist of a good flat stone, dressed on all sides. Heading courses. In every brick wall every sixth course of brick shall be a heading course, except where walls are faced with brick, in which case every fifth course shall be bonded into the backing by cutting the course of the faced brick, and putting in diagonal headers behind the same, or by splitting face brick in half, and backing the same by a continuous row of headers. Stone ashlar. In all walls which are faced with thin ashlar, anchored to the backing, or in which the ashlar has not either alternate headers and stretchers in each course, or alternate heading and stretching courses, the backing of brick shall not be less than twelve inches thick, and all twelve-inch backing shall be laid up in cement mortar, and shall not be built to a greater height than prescribed for twelve-inch walls. All leading courses shall be good, hard, perfect brick. Brick backing. The backing in all walls, of whatever material it may be composed, shall be of such thickness as to make the walls, independent of the facing, conform as to thickness with the requirements of sections five and six of this act.

"SEC. 10. Isolated piers, how constructed. Every isolated pier less than ten superficial feet at the base, and all piers supporting a wall built of rubble stone or brick, or under any iron beam or arch girder, or arch on which a wall rests, or lintel supporting a wall, shall at intervals of not less than thirty inches in height, have built into it a bond stone not less than four inches thick, of a diameter each way equal to the diameter of the pier, except that in piers on the street front, above the curb the bond stone may be four inches less than the pier in diameter; and all piers shall be built of good, hard, well-burnt brick and laid in cement mortar, and all bricks used in piers shall be of the hardest quality, and be well wet when laid. Walls and piers under girders and columns. And the walls and piers under all compound, cast-iron, or wooden girders, iron or other columns, shall have a bond stone at least four inches in thickness, and if in a wall at least two feet in length, running through the wall, and if in a pier, the full size of the thickness thereof, every thirty inches in height from bottom, whether said pier is in the wall or not, and shall have a cap stone of cut granite, at least twelve inches in thickness, by the whole size of the pier, if in a pier, and if in a wall, it shall be at least two feet in length, by the thickness of the wall, and at least twelve inches in thickness. Base stone. In any case where any iron or other column rests on any wall or pier built entirely of stone or brick, the said column shall be set on a base stone of cut granite, not less than eight inches in thickness by the full size of the bearing of the pier, if on a pier, and if on a wall the full thickness of the wall. Hollow walls. In all buildings where the walls are built hollow, the same amount of stone or brick shall be used in their construction as if they were solid, as above set forth ; and no hollow walls shall be built unless the two walls forming the same shall be connected by continuous vertical ties of the same materials as the walls, and not over twenty-four inches apart. Height of walls, how computed. The height of all walls shall be computed from the curb level. Swelled or refuse brick, use of, prohibited. No swelled or refuse brick shall be allowed in any wall or pier; and all brick used in the construction, alteration, or repair of any building, or part thereof, shall be good, hard, well-burnt brick. Bricks to be wet. And if used during the months from April to November, inclusive, shall be well wet at the time they are laid.

"SEC. 11. Mortar, of what materials, and how used. The mortar used in the construction, alteration, or repair of any building shall be composed of lime or cement, mixed with sand, in the proportion of three of sand to one of lime, and two of sand to one of cement, and no lime and sand mortar shall be used within twenty-four hours after being mixed; and all walls or parts thereof, below the curb level, shall be laid in cement mortar, to be composed of cement and mortar, in the proportion of one of cement to two of mortar. No inferior lime or cement shall be used. Sand. And all sand shall be clean, sharp grit, free from loam; and all joints and all walls shall be well filled with mortar.

"SEC. 12. Walls, how carried up and anchored. In no case, shall the side, end, or party wall of any building be carried up more than two stories in advance of the front and rear walls. The front, rear, side, end, and party walls of any building hereafter to be erected shall be anchored to each other every six feet in their height by tie anchors, made of one and a quarter inch by three-eighths of an inch of wrought iron. The said anchor shall be built into the side or party walls not less than sixteen inches, and into the front and rear walls at least one half the thickness of the front and rear walls, so as to secure the front and rear walls to the side, end, or party walls; and all stone used for the facing of any building, except where built with alternate headers and stretchers, as hereinbefore set forth, shall be strongly anchored with iron anchors in each stone, and all such anchors shall be let into the stone at least one inch. The side, end, or party walls shall be anchored at each tier of beams, at intervals of not more than eight feet apart, with good, strong, wrought-iron anchors, one-half inch by one inch, well built into the side walls and well fastened to the side of the beams by two nails, made of wrought iron, at least one fourth of an inch in diameter; and where the beams are supported by girders, the ends of the beams resting on the girder shall be butted together end to end, and strapped by wrought-iron straps of the same size, and at the same distance apart, and, in the same beam as the wall anchors, and shall be well fastened."

Preservation of Stone. - In the preservation of stone we now lay down, from the highest practical authorities, the condition upon which only a successful issue can be obtained : First. The materials must be irremovable and imperishable.

Second. They must be easily absorbed by, and thoroughly incorporated with the stone.

Third. The materials must be free from color, but admit of imperishable coloration.

Mr. Frederick Ransome's process seems to best fill all the above conditions, meeting most thoroughly every possible requirement. The materials used are as follows: Dissolve flint or silicate of soda and chloride of calcium. Flint or silex is soluble by heat under pressure in a solution of caustic soda. In this form it is soluble silicate of soda. In this form it is to be thoroughly brushed into the stone. On top of this is brushed into the stone a solution of chlorine, which unites with the soda, forming an insoluble silicate of lime. The silicate of lime being white, there is an opportunity of using metallic tinting solutions.

Another process for the preservation of stone or brick is to dissolve resin (rosin) with turpentine, and when heated, to add linseed oil to form a paint.

Another mixture is made from unslacked lime, to which is added while slacking oil of tallow. When the slacking is complete, it is placed in a vessel with alum water and protosulphate of iron. After settling, it is drawn off and used.

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Another process is the repeated application with brush of a solution of beeswax in coal tar naphtha; when the color of the stone is to be preserved, white wax, dissolved in refined distilled camphene.

None of these, except the first, seem to offer any practical purpose, and only offer a temporary protection.

Here is a mixture, given by M. Kuhlman, that seems to have been used with success for thirty years. It is the silicate of potash. Before application the surface requires to be washed with a diluted solution of caustic potash with a hard brush. Three applications of the silicate are required during three days.

There is an English preparation extensively used for this very purpose of repelling moisture, and for the preservation of stone, brick, plaster and cement. It is a liquid or solution of silica. It is also used in kitchens, cellars and basements to form a hard surface on the walls, impenetrable to water. It is a kind of enamel, and is put up in barrels and by the gallon, and is red, white, blue, green and chocolate. It is applied with a brush, and is very inexpensive. It presents a surface like glazed tile, and is not affected by water or atmospheric changes. It is a silicate enameling paint. There are several agencies in the United States.

Incrustations on Brick Walls. - A greyish white substance, that appears on the surface of bricks, before being laid on walls, and afterwards; it proceeds from several causes: and since the discoloration is very unsightly, and if removed, may return, many builders and owners of buildings have tried various ways to get rid of this precipitate. It occurs generally on Philadelphia and New Jersey bricks for front facings. It is not seen often on the Baltimore or North River bricks. Limes that are burned of magnesian limestone produce a lime with a mixture of magnesia, and when made into mortar, and used in brickwork, absorb sufficient vapor from the atmosphere to form a sulphate of magnesium or epsom salts. It finds its way through every crevice and pore out to the surface. This sulphate of magnesia is found in a crude form known as silicate of magnesia, in native forms as asbestos, soapstone, talc and French chalk. When common salt is used in solution on brick, it leaves a white precipitate when dry. Portland cement contains but a small proportion of magnesia, and walls built with it show but little, if any, defacement. Some of the grades of Rosendale cement that contain magnesia and soda disfigure the surface of the walls when used in cement mortar. The best remedy is to remove the incrustation and wash the fronts, and when dry, paint the surface. If the surfaces are painted over the incrustations, it shows different shades of color when the paint is dry. This discoloration of brick walls is most noticeable in dry weather on parts of walls subject to dampness, and on entire walls after heavy rains. North and East walls are usually the heaviest coated. This white precipitate comes from both bricks and mortars.

To avoid this white defacement, builders should use limes free from magnesia; and cements free from magnesia and soda.

Avoid using bricks that are burned with coal, and also when the dry surface of the brick is whiter than the true