ECONOMICAL POND CONSTRUCTION 29 



forming the tank bottom. The side-walls 

 were then moulded by means of the outer 

 tapered box (B) and an inner correspondingly 

 shaped box (C), the two boxes being con- 

 structed of rough boards joined respectively 



Here is a section of the concrete tank showing method of construction. 

 (References in text.) 



on their outer and inner sides by upright 

 cleats (D). These boxes had their walls 

 spaced apart a distance equal to the thick- 

 ness of the walls to be formed, and were 

 placed in position as soon as the bottom frame 

 had been filled. They were fastened to- 



