PLATE XXIX.

The method of cutting the bricks for a cylindro-cylindric arch, and two different methods for the joints of the heads of niches. Fig. 1 the cylindro-cylindric arch, with a frame of wood so constructed, that the two horizontal pieces have their outer edges in circles concentric with the circle of the wall: this is shown by the plan of the wall No. 2. The edges of the circular pieces are graduated with divisions perpendicularly over each other, A B: No. 2. is a rule to be moved vertically along the said concentric edges, which vertical position is always known by the corresponding divisions; on the front edge of the rule is a hook projecting so as to come to the cylindric surface of the wall: the hook is shown at No. 3, with a part of the rule. The use of this machine is for drawing the edges of the bricks in order to cut them to the circle.

Fig. 2 two different methods of forming the joints for the heads of spherical niches. In the right hand half the joints run horizontally, but this is a very bad method; as all the beds are conical, the bricks at the summit have little or no hold. In the other half the joints run radially in planes from the face to the centre. The work is not only more firm when executed by this last method, as bedding the courses on planes, but much more easily executed; nothing is more difficult to form than conical surfaces; and in this both conical and spherical surfaces occur; whereas when the joints run radially, only the spheric surface occurs, which may be formed by one bevel, only one side being straight and the other circular.

PLATE XXX.

Shows the method of steening wells.

The first thing is to make a centre, which consists of a boarding of inch or inch and a half stuff, ledged within with three circular rings. The bricks are laid between these rings, and all headers. The wide joints next to the boarding are filled in with tile or broken bricks. Where the soil is firm, centreings are not necessary, but they are requisite in sandy ground. The centreing remains permanently with the brick work; as the well digger excavates the soil, the first centre sinks, then a second centre is made, and put above the first, and built in with brick work in the same manner: and thus the number of centreings depend on the depth of the well. This method is that used in London: but in the country other methods are used. One is with several rings of timber without the boarding: they first build upon the first ring, four or five feet, then a second ring, and build again, and so on to the depth of the well. This however is not so good a method as the foregoing, as the sides of the brick work are very apt to bulge, particularly if great care be not taken in filling and ramming the sides in uniformly, so as to press equally at the same time.

Abstract of the Building Act, as far as regards the Bricklayer, 14 GEO. III. which refers only to London, and the several Parishes within the Bills of Mortality.

Every master bricklayer to give twenty-four hours notice to the Surveyor of the district from the first to the seventh rate, concerning the building to be altered or erected; but if the building is to be piled or planked, or begun with wood, it becomes the business of the carpenter to give such notice.

The footings of the walls are to have equal projections on each side but where any adjoining building will not admit of such