502 
IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
the work which must he performed is worthy of notice. In ad- 
dition to the widely differing subjects of bacteriology, microbi- 
ology and chemistry of water, miscellaneous chemical and bac- 
teriological work must be entered into. If the laboratory man 
is also an engineer, so much the better. 
I was surprised on first preparing my chart to see how re- 
cently the laboratories listed had been installed. Beginning 
with the one maintained by the city of New York since 1897 
and that of Utica, New York, established in the same year, we 
have a rapidly increasing number of laboratories established 
during the succeeding nineteen years. Six plants with a com- 
bined average pumpage of 32.5 millions gallons per day are 
now installing laboratories. 
Twelve plants with a combined pumpage of 45 million gal- 
lons per day have daily examinations made at outside labora- 
tories. The Metropolitan Water District which supplies Boston 
and some neighboring communities is a State Commission. It 
maintains its own laboratory and supplies a little more than 100 
millions of gallons of water daily. 
Of the plants reporting twenty-one are owned privately, sixty- 
eight municipally and one by the United States Government. 
The employees of twenty-eight of the municipally owned plants 
and those of the Government plant are selected by civil service 
methods. 
Rivers and streams form the direct source of sixty-two plants 
out of the ninety that have their own laboratories, the remain- 
ing sources are lakes, impounded waters from more or less satis- 
factorily protected watersheds and in a few instances wells and 
infiltration galleries. Those plants which do not maintain lab- 
oratories are nearly all using the water of wells, or impounding 
reservoirs. None of them supplies more than an average pump- 
age of 16 million gallons per day. One or two pump direct 
from streams without treatment. 
Artesian waters and the waters of great impounding reservoirs 
are to be expected to be of uniform composition and quite con- 
stant in their bacterial contents. Occasional growth of algae 
may require copper treatment to avoid odors and tastes, but 
otherwise the water should be very uniform. Rivers, small reser- 
voirs and lakes and shallow wells are very likely to be incon- 
stant. Raw water from such sources is subject to very sudden 
alteration with consequent need for an immediate readjustment 
