CONSTRUCTION NOTES 349 



extend in a direction perpendicular to the direction of the rods at the top 

 of the floor. The depth of the concrete in the floor should approximate 

 eight inches. The thickness of the side walls if reinforced will approximate 

 12 inches. If these side walls are not reinforced the thickness will approxi- 

 mate from 14 to 17 inches and may be affected by the width of the pro- 

 posed coping. If the pool is more than three feet in depth it will probably 

 become necessary to reinforce the side walls, otherwise in shallow pools, 

 used mainly for reflection purposes, it is not necessary to reinforce the 

 concrete. 



The mixture for concrete should be one part cement, two parts sand 

 and three parts screened gravel or crushed stone. In connection with 

 shallow pools where the surrounding soil is of a sufficient texture to support 

 itself in a vertical position, the natural soil may sometimes be used as a 

 substitute for any outside form. Specially constructed forms will be neces- 

 sary if any drainage of the surrounding soil is necessary. The problem of 

 constructing forms for the inner face of walls is important. It is often 

 necessary, especially where it is practicable to pour the bottom and the 

 walls as a unit, to suspend the forms for the inside surface of the walls. 

 Wherever the inside surface of the pool is to be veneered with any material 

 such as stone, brick or tile it is quite necessary to place small ties in the 

 inside face of the concrete wall in order to hold the veneering in place. 

 This is not essential on the bottom of the pool. The use of any material 

 to veneer the inner surface of the pool does not reduce the thickness qf 

 the proposed concrete walls. 



Coping. The coping may be installed as shown in the drawings accom- 

 panying this discussion. The two important points to be considered in the 

 proper construction of the coping are: (i) To provide dowels for holding 

 the coping permanently in place. (2) Wherever the coping overhangs the 

 outer face of the wall a cinder fill should be provided so that the vertical 

 action of frost will not dislodge the coping. 



Outlets and overflows for pools. On Plate 147, figures 2 to 6, are shown 

 various types of outlets and overflows for garden pools. The first principle 

 of a correct overflow is that the overflow should remove the water from the 

 surface instead of from the bottom of the pool in order thus to remove 

 constantly a certain proportion of the dust and dirt which must collect 

 on the surface water of any pool. (See Plate 147, figures 3 and 4.) The 

 type of overflow shown on Plate 147, figure 5, is not desirable because it 

 removes the water only from the bottom of the pool and thus it becomes 

 necessary to clean the surface of the pool either by draining the pool entirely 

 or by removing the scum of dust and, dirt through other artificial methods. 

 This type of overflow (Plate 147, figure 5) should always be provided with 



