result if a number of half and quarter blocks were necessary to make each course. While the design of a large chimney is not within the duties of the concrete worker, yet the specifications for a concrete block-chimney of similar design to the one shown in Fig. 5 will be of interest. The foundation was placed 6' in depth and 20' square, with the reinforcement in foundation placed 5' below the top of foundation; this was made up of 1" bars spaced 11" apart in each direction, with 8 bars placed diagonally from corner to corner in each direction, spaced the same distance apart. The wall of chimney for the first 70' was made up of 9" blocks, in which was placed 1" vertical bars spaced 91⁄2" apart with "horizontal rings spaced 8" apart, or one in each course of blocks. The inside diameter of flue was 5', the entire height with the outside diameter 6' 6" for the first 70', and 6'1" for the next 80', or balance of height; thus using a 63" block in which "vertical rods were spaced the same distance apart as for those below. The " rings in the last 80' of height were placed 16" apart, or in each second course of blocks. At Fig. 6 is shown the easily constructed mold for the chimney-block illustrated in Fig. 5. This is easily made by employing two planks for the sides and by dividing these into spaces, equal to the height desired for the blocks, and then cutting a saw kerf for a distance of 3" into the top edge of plank, into which are fitted sheet-iron dividing-plates, as shown in Fig. 6. These dividing-plates are cut with a shoulder and projecting-end, which fits into the saw kerf and projects at least 1" beyond the plank. Through this a hole is punched, and by inserting a short rod in same, the plank sides are held securely against the sheet-iron dividing-plates. The two edges of the sheet-iron dividing-plates are cut to conform to the segment of the curve in which the block is to be molded; the dividing-plate rests upon a convex form in the bottom of the mold that has the same curve as the edge of the dividingplate. This form is easily constructed of sheet-iron, and wood strips cut in a proper segment of the circle. At one side of the mold a beveled strip is nailed, which molds the channel in one end of the block, as illustrated. This strip is nailed to the side plank and then cut so that the sheet-iron dividing-plate will go into the saw kerfs. At the opposite side of the mold, or upon the other plank, a square and also a beveled strip are nailed, to form the mold for projection upon the opposite end of block. The sheet-iron dividing-plates are punched to admit the gas-pipe employed as cores. These are well greased before being placed in the mold, so as to permit them to be the easier withdrawn from the concrete. This form of mold permits a wet mix to be used, and a series of blocks to be molded closely together; thus saving space in the shop or yard. To prevent the molds warping from the moisture in the con 30 MOLDING CONCRETE CHIMNEYS crete, they should be well coated with oil and then given a coating of shellac before using; this will also act as a preventive of the concrete adhering to the wood or sheet-iron dividing-plates. Where the blocks are to be molded of varying thickness, the same bottom form to mold may be used each time, as the curve or segment of circle upon the inside of the block will not be changed; requiring simply wider side planks, as these mold the thickness of the block, and dividing-plates of the same width. FORMS FOR LARGE MONOLITHIC CONCRETE CHIMNEYS The forms for a large monolithic concrete chimney demand that they be rigid and amply strong, so as to preclude any possibility of an accident which the extreme height of the work would render fatal. They must also be easily raised, as the difficulty of applying tackle to the forms at the height they must be carried demand this; they must also be adjustable, so that the walls of the chimney can be given the proper batter. When this can be secured without abrupt changes in the wall it will be far more satisfactory than to change the thickness all at one point. The outside molds shown at Fig. 7 are adjustable to a difference in circumference of 20", thus permitting a 9" wall to be constructed at the bottom of the chimney and from that gradually decreasing to a 6" thickness of wall at the top. This is accomplished by the strips of strap-iron used to join the sections |