THE PURITY OF DRINKING-WATERS. 131 
the location of a well and its depth. In very deep wells bacteria 
have a chance to be filtered out of the water as it passes through the 
soil before it reaches the well, so that, if care be taken to prevent 
contamination at the surface, the water is safe. This is always true 
of artesian wells. But in the shallow well the chance of dangerous 
contamination is great. The most common, as well as the most 
dangerous contamination of well-water, comes from the privy vault. 
Both vault and well are, for convenience, placed near the house and 
frequently near each other. The well is sunken several feet below 
the surface of the ground, while the vault is close to the suiface. 
The contents of the vault inevitably soak into the ground and will be 
surely distributed in every direction, taking naturally the course of 
water currents under the surface. It is almost certain that, if the 
well is close at hand, the water courses will lead to it and the con- 
tents of the vault will thus find their way into the well. It requires 
no argument to demonstrate the danger from such conditions. Nor 
will anyone familiar with agricultural communities fail to recognize 
that exactly such conditions frequently exist. Indeed, they are 
sometimes even worse than this, for one may find the vault actually 
upon an elevated mound and the well sunk into the soil at its foot 
not twenty feet away. 
Under such conditions one need not be surprised at the spread of 
typhoid. A single case of the disease on the farm will contaminate 
the vault, and may soon infect the well. The infection may be 
from water percolating through the soil or from surface currents in 
time of rains, washing the contaminated water into the mouth of the 
well. The farmer rinses his milk pails in the water from the well 
and subsequently puts his warm milk in the cans. The typhoid 
bacilli which were in the well thus get into the milk, where they 
find conditions for rapid growth, and the farmer, wholly unconscious 
of having done anything out of the way, distributes the bacilli to the 
neighboring community which he supplies with milk. A typhoid 
fever epidemic breaks out which remains a mystery, unless some one 
is sharp enough to trace it to its source in the farmer's well. 
Such is not an imaginary instance, but represents a type of 
typhoid epidemic many times repeated. It is simply illustrative of 
