ere
killed, but no small ones; numerous small (less than two inches long)
'sunfish' were killed, but no large ones.

"The wind brought the dead fish to the corners of the reservoir, and
it was very little trouble to remove them. No dead fish were seen
twenty-four hours after completion of the treatment."

The injury done by copper sulphate to fish is a more serious matter
than was at first supposed. Brook trout are, apparently, the least
resistant to the salt. A Massachusetts trout pond stocked with
eight-inch trout lost forty per cent as a result of the introduction
of a strong solution of copper sulphate. The Bureau of Fisheries is
working in conjunction with the Division of Plant Physiology in this
matter, and it is hoped to secure reliable information. In the
meantime, owners of ponds stocked with game fish would do well to take
great care before resorting to the copper cure for algae--that is, if
they hesitate to lose a part of the fish.

_Water May be Drunk During Treatment_

When a pond or reservoir is treated with the proper amount of copper
sulphate to remove algae--except in the case of the few very resistant
forms requiring a stronger solution than 1 part of copper to
1,000,000 parts of water--there is no need of discontinuing the use
of the water supply during treatment; the water may be drunk with
impunity. But when water known to be polluted with pathogenic bacteria
is sterilized by means of copper sulphate in strong solution, it is
just as well to discontinue the use of the water for drinking purposes
for not more than twenty-four hours. Even then, this is an overcareful
precaution rather than a necessity.

Experiments conducted with great care and thoroughness demonstrate
that at room temperature, which is near the temperature of a reservoir
in summer, a solution of 1 part of copper to 100,000 parts of water
will destroy typhoid bacteria in from three to five hours. Similar
experiments have proved that a copper solution of like strength is
fatal to cholera germs in three hours, provided the temperature is
above 20 deg. F. As was the case with algae, bacteria were found to be much
more sensitive to copper when polluting water than when grown in
artificial media.

_The Use of Copper Tanks_

The toxic effect of metallic copper upon typhoid bacteria in water
gives some hints as to prevention of the disease by the use of copper
tanks. This should not altogether take the place of the boiling of th