a manual of practical hygiene for students physicians and health officers tast ilic first beds constimutcd hy sitnpson vltr broad basins twlv icctin ipth witb impervious boloins and sides containing layers of hutuoifgravhil and sanneatli tlu stontaswere laid ordinary drain jipes throiijh vhili the liltererl water wahdischarn ed as th top layers of sand became cgtltlt they wereseraped and renewed the beds of i he present day are cltnstrulttd onvry similar lins they are virliially immense tanks of varying sizeshae and eonstrue 2akfcy1.jpg from vk pth c 10 yo View Photo