The nitrogenous matters in bad water are just what plants like to feed on. Plants in streams tend to purify the water, and the roots of trees around cesspools feed on matter that might, but for them, get into the wells of drinking water near by. A weeping willow near outbuildings, has a much mightier influence for good on the health of those in the vicinity, than by the mere shade which it affords. In all the worry about drinking water which the mere chemist makes, the public forgets to take counsel of the biologist. Nature has so nicely balanced her ominiscient forces, that though the chemist can show us that we are everlastingly in danger of destruction, the physiologist knows that she is only in fun; and that though she dangles us over the abyss with one hand, she takes care to catch us with the other.