108 Thirty-fourth Annual Meeting. 
prevailing there and I have been adding copper sulphate to the 
water in a proportion of one to one and one-half million. On 
another trial I used one part to one million, and I find that that 
can be done without harming the trout, while it is fatal to this 
organism when you make experiments in tubes within a few 
hours, so that there is at least a fair chance of keeping the water 
constantly sterilized of this organism and of many others. It 
reduces immensely the total bacterial contents of the water, and 
the chances are that it will kill this trout organism. Since the 
use of the copper sulphate the death rate has been reduced, but 
that may be a coincidence, as the death rate usually falls at this 
time of the year. We hope another year, with the permission of 
the Wisconsin Commission, to commence the treatment, say a 
month before the disease is expected, which is about the first of 
June; and we will start in with the copper sulphate about the 
first of May, with a constant flow, and continue that all through 
the summer months, until the water cools off. It is the cooling 
off of the water at that station which checks the disease, because 
the microorganism cannot grow in cold water. We have a 
remedy here which can be applied on a larger scale, and with 
an even chance, it seems to me, of success. It will probably 
either be entirely successful or fail entirely. 
Now, whether we can go further and apply that to the 
disease that Mr. Whish has at his station, is another matter. 
There is only one way to get very much evidence on it, and that 
is to try it in the water itself. 
As the trout at Mr. Whish’s station are extremely susceptible 
to copper sulphate, very much more so than at Bayfield, and as, 
if you use one part of copper sulphate to six and one-half million 
parts of the water, will kill the domesticated fry at Cold Spring 
Harbor hatchery, you must use one to seven million to be safe ; 
that reduced greatly the amount of copper, and very likely the 
solution would be too weak to do any harm to the organism. Per- 
haps at some future time we may find another cheap poison 
which can be used on a large scale, but at the present time cop- 
per sulphate is the only one that offers any chance of killing the 
organism without killing the fish. 
Mr. North: When I went to the Hammondsport hatchery 
it was as far from nature as possible. The brood ponds there 
