48 New Yoiik Stvtk 



test, even though it be rough in itself and though its use be dis- 

 tinctly favorable to the cause of the manufacturer rather than to 

 the protection of the fish. 



In order that the test may be properly applied, it is necessary 

 to take a group of minnows and divide them into two parts, placing 

 one in a cage or float that is anchored in the stream above the point 

 of contamination and another in a similar cage or float that is 

 placed in the stream enough below the point of entrance of the waste 

 material that one can see it is reasonably mingled with the waters of 

 the stream proper. If after a short period the minnows in the lower 

 cage are dead, the upper cage is then examined and, if the fish 

 are living, it is transferred to the position of the down stream cage. 

 The death of this second lot of fish will then establish very positively 

 the fact that the wastes are injurious to the fish life in the waters. 



Serious Conditions Proved by Test 



Some attention must be paid to the variability of this test and its 

 relative value in determining the injurious character of trade wastes. 

 The minnow is a small fish and generally is of a type fairly 

 sensitive to water pollution. It does not represent the varieties that 

 are most sensitive, like the trout, and on the other hand it is far 

 more susceptible than such fish as the carp and bull-head, which are 

 known to be relatively indifferent to pollution. One should not 

 forget that Forbes found the common shiner was " unusually 

 tolerant of polluted w r aters, ,} and this species if collected by any 

 persons and used for the test would vitiate the results. It is 

 recognized, furthermore, that the most sensitive stages in the history 

 of any fish are those of its youth, the fingerling and fry stages 

 being far more susceptible to injurious influences than the half- 

 grown or full-grown fish. Accordingly, if the effect of the wastes 

 on minnows or young fish collected as such is clearly injurious, 

 then one can confidently affirm that no stronger argument is needed 

 to establish the serious contamination of the stream, in that any 

 effect produced in the short time that has usually been utilized for 

 these experiments is in itself conclusive beyond possible criticism. 

 It will readily be recognized in a moment's consideration that, un- 

 doubtedly, many contaminations are injurious to fish in the long run 

 and yet these influences would not display themselves in any 

 measurable fashion within the brief period of such a test. 



Shelford maintains that to make safety tests reliable in character, 

 fish should be able to live at least one month in water under standard 



