WATER SUPPLY. 



123 



may be put on above it, until the whole is completed. 

 In digging, a shoulder a foot in width is made on the 

 top of the sub-soil eighteen inches deep, to rest the beams 

 upon. This is also covered with cemfent, and the beams 

 are laid on, and the spaces between them on the shoulder 

 are filled in with stone, or brick, and cement, to the 

 upper level, upon which the floor rests. A strong floor 

 of four-mch plank, doubled, with the joints broken, is 



Fi^. 20.— KAIN-WATEK CISTERN. 



laid upon the beams and covered with a coat of the cement 

 to exclude surface water ; and this floor is then covered 

 with earth and sodded oyer, or a platform is built over 

 it to stand upon. A manhole (m) should be made in the 

 cover large enough for a person to go down when it is 

 necessary to clean out the cistern, and this is brought up 

 a little above the platform and fitted with a tight cover, 

 kept locked, to avoid danger of children falling m. The 

 pipe (e) conveys the water from the roof; but it is best 



