118 TRANSACTIONS OF THE [FEB. 18, 
sea, when a wave causes the bottom layers to flow up-stream 
while upon the top the current continues down-stream. 
In 1859, I was called to gauge the natural flow of a stream 
upon which were three mills at intervals of about four miles. 
The lower mill depended for its power upon the natural flow; 
the two other mills depended upon dams. On one occasion, 
the upper mill had been idle for several days, and the water 
overflowed the weir. ‘The vegetable matter in flotation made it 
evident that a well-defined current existed through the pond, 
while beyond the current laterally there was no real flow. 
In any artificial pond it is natural that there should be a 
stagnant belt. 
In the idle mill-pond here referred to, it was observed that 
the water had a discoloration and also an objectionable taste, 
and that both of these extended to the whole body of the 
pond;—thus proving that the impurities of the stagnant parts 
of the pond can be taken up into the water of the current. 
Fish taken from the pond, after being cooked, had the same un- 
pleasant flavor. The water of the stream above the influence of 
the impoundment was clear and agreeable to the taste. The 
discoloration and peculiar flavor of the water, it is believed, 
were derived from organic growth and decomposition in the 
stagnant portion of the pond. 
Inflow and outflow must cause a current through the pro- 
jected Quaker Bridge reservoir; but the amount of outflow 
being limited, the current volume through the pond must also 
be limited. The undischarged mass must continue in a differ- 
ent state from that of the current volume that is directly im- 
pelled to flow. Quiescence and flow must be natural conditions 
co-existent in the pond. 
The eminent Dr. John C. Peters, of this city, in his testi- 
mony before the Aqueduct Commission, is reported as saying 
that ‘‘ there is no danger of any stagnation at all.” This is all 
that he is stated to have said upon the very interesting and im- 
portant subject of stagnation in the projected Quaker Bridge 
Dam. What has already been remarked would seem to deter- 
mine that Dr. Peters is in error. Were it shown that there 
must be a region of stagnant water in the projected Quaker 
Bridge Pond,—would he still decide in its favor ? 
Water has the power—whether in flow or not—to take up 
impurity from any deleterious substance with which it is in con- 
tact. It is not intended that the main volume of the great 
pond at Quaker Bridge shall ever be discharged. Contamina- 
tions, therefore, carried into it from above and settling upon 
the bed, will there remain, a source of impurity and injury to 
the entire waters of the pond. Vegetable matter falling to the 
