16 DEPARTMENT OF THE NAVAL SERVICE 
7 GEORGE V, A. 1917 
higher plants such as dandelions and wild mustard, is of importance in agriculture. 
Dr. George T. Moore (U. S. A. Plant Industry Bulletin 76, issued 1905) has demon- 
strated the practical application of this to the purification of water supplies containing 
objectionable alge. The method of using the copper is to dissolve copper sulphate in 
the water to the extent of one part to from five millions to twenty millions of water. 
This dilution served to kill such delicate forms as those producing the well known 
water bloom of August aud September. For the more hardy organisms such as diatoms . 
it was found that the amount of copper sulphate required was as high as one part or 
more per million parts of water. The results quoted above were accepted as correct, 
and the effect of such solutions of copper sulphate on lobster larve was examined. 
Vigorous larve, placed in fresh sea-water containing one part copper sulphate per mil- 
lion of water, all died within three and a half hours, although four-fifths of them lived 
for more than two hours. Another lot of the same copper sulphate solution was diluted 
to contain one part of copper sulphate in two million parts water. In this the larve 
lived more than four hours, but all were dead within six hours. In another lot of the 
solution diluted until there was only one part copper sulphate in three millions of 
‘water, the larve lived but little longer. 
Fig. 4. 
Drawing of lobster larva two hours after natching. 
No diatoms could be found attached to it. 
Control experiments, exactly similar in every respect, except that the water con- 
tained no copper sulphate, were made in each case, the lobster larve remaining 
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