By referring to the cross-section of the secondary beam, it will be noticed that it is jug-shaped, shelves being left on either side for the support of the roof forms, which were placed after the secondary beams had been properly grouted to the radial ones. The lagging was laid diagonally, so that the short diameter was slightly greater than the distance between the beams. This greatly facilitated the removal of the lagging, as it was merely necessary to strike the wedge-shaped fillets beneath, and turn them clockwise, after tearing out the end lagging. [Illustration: PLATE IX, FIG. 1.--VIEW OF SEPARATELY MOULDED SECONDARY BEAMS IN YARD BELOW SOUTH RESERVOIR.] [Illustration: PLATE IX, FIG. 2.--SETTING PRIMARY BEAMS, SOUTH RESERVOIR.] The writer believes that the adoption of forms of this type, rather than the ordinary kind, led to a saving of lumber of about 400,000 ft. b. m. During the erection and placing of the concrete, all the joining surfaces were carefully picked and cleaned, particular care being taken at the junction of the secondary with the radial beams, and the upper surfaces of all beams before laying the roof slab. After the greater part of the roof was completed, the floor was laid in those sections where it was protected from the sun's rays. The concrete was placed in two 15-cm. thicknesses, and the work was carried on night and day, without any joints. The laying of the floor occupied 8 days, or an average of nearly 100 cu. m. daily. [Illustration: PLATE X, FIG. 1.--VIEW OF COMPLETED SECTION OF SOUTH RESERVOIR. EXPANSION JOINTS IN SIDE-WALL NOT YET FILLED.] _Proportions of Concrete._--All the concrete work was brought to a smooth face by careful spading, no plastering being used throughout the reservoir, except in the superstructures. The work was kept well watered in every case for about 15 days. The whole of the concrete work in connection with the reservoir was completed in 5-1/2 months. The concrete for the columns and foundations was a 1:3:5 mixture, the aggregate consisting of equal parts of 19-mm. (3/4-in.) and 38-mm. (1-1/2-in.) crushed stone. The remainder of the concrete, except that for the roof, was a 1:2:4 mixture, the aggregate also consisting of equal parts of 19-and 38-mm. stone. With the exception of a short length of the side-walls, the sand used was that manufactured by the Company. When the crushing plant was unable to produce all the sand required, the Hornos sand (see Table 3) was used in the side-walls in equal proportions with the crusher sand.