583 
The following figure shows how a cesspool may pollute a well, 
even though the' cesspool is at a lower level than the top of the well: 
Fig. 55. — Showing pollution of a well by a cesspool situated on a lower level than the top of the well. 
Harrington: Practical Hygiene; Phila. and N. Y., 1901, p. 324. 
The ground immediately around the well should be protected from 
stray animals by a fence or otherwise. The shaft of the well should 
be thoroughly tight and for this reason the use of terra cotta tiles or 
metal pipe, for the shaft is to be preferred to walling up with bricks 
and mortar. In any event the space immediately around the shaft 
proper should be puddled with clay or cement, or, as advised by Koch, 
have the upper part packed around with sand. The use of open wells 
or even the use of chain pumps is not to be recommended, since they 
are more or less liable to pollution from the introduction of impurities 
down the shaft. In all cases the well should be guarded by a tight 
coping and cover. A device sometimes resorted to, and which is an 
advantage, is to cover over the well with a tight cover and to place 
the pump to one side of the well shaft with an elbow connection. 
A form of well, known variously as the tube, or driven, or Norton, 
or Abyssinian well, is good from a sanitary point of view. It consists 
merely of an iron pipe screwed together in sections driven down to the 
water-bearing layer. The lowest section of pipe is armed with a point 
and is perforated with a number of holes. In a well of this character 
there is no danger from seepage into the shaft and it is cheaply and 
quickly constructed. In case one such well fails to furnish sufficient 
water others can be driven alongside and all connected with one pump. 
Every precaution should be taken to prevent the contents of the 
cesspool soaking into the soil, for even if the cesspool is at a distance 
from the well the ground between will eventually become saturated 
and fail to act as a filter. As stated above, the presence of an imper- 
vious stratum between the well and the cesspool is a good protection, 
but where such a condition does not exist the cesspool should be made 
water-tight. The crude methods of sewage disposal still quite com- 
monly in vogue in the country lead to a continual menace of polluting 
the water supply. 
