1888.] 151 
A serious question is that of change occurring in waters long 
impounded in reservoirs; but he believes, with Mr. E. F. 
Smith, that the waters of such reservoirs drawn from a dis- 
tance of at least six or eight feet below the surface and as much 
above the bottom, so as to avoid the confervoid and bacterial 
growths near the surface, and the organic remains of previous 
life which settle to the bottom, would give the best results at- 
tainable. It has been shown also, by experience, that water 
contaminated with organic matter has a tendency to purify it- 
self, in rapidly flowing streams interrupted by cascades or rif- 
fles, by the growth of animals and plants of the lower orders. 
While speaking on the subject, he would allude to the excel- 
lent character of the water supply from the Schuylkill as to 
its solid ingredients. Water may be too pure, ?.e., deficient in 
those salts and earthy matters which tend to maintain tissue- 
metamorphosis and growth; lime salts in moderate quantity 
are beneficial, while magnesian are irritant, purgative and un- 
satisfying to the thirst—as are the waters of the Paris basin—— 
while excess of lime salts, as in the Mississippi Valley, gives 
rise to calculous concretions. Many diseases can thus be traced 
to defective water supply. 
The greater amount of organic matter in the water of the 
upper Delaware is the result of its drainage from the swamps 
and vegetable decaying matters on the mountains above the 
Water Gap. Much of the impurity of the Schuylkill is gotten 
rid of in the precipitation which occurs in its course from the 
traversing by its waters, acidulated from the mines, of the 
limestone bed of rocks above Reading. 
Mr. McKean was of the opinion that the assumption, be- 
cause there is some albuminoid matter in the water we get 
from our hydrants, it is therefore unwholesome, was unfounded. 
He was doubtful if it had been made clear that the albuminoids 
and other matters presumably unwholesome, found in the sup- 
ply of drinking water as furnished to us, are really unwhole- 
some unless accompanied by antecedent extraneous fever 
germs. He adverted to the low death-rate of London and 
Philadelphia as militating against the theory of the great un- 
wholesomeness of their drinking water. 
