April 21, 1905.] 



SCIENCE. 



619 



vaults and infected places where crude 

 methods were ineffective. That it is highly 

 toxic in so extremely dilute solutions seems 

 almost beyond belief, yet the experiments' 

 outlined by the speakers successfully bear 

 all the scrutiny which I have been able to 

 give them and seem to substantiate all con- 

 clusions drawn from them. 



In connection with the application of 

 copper sulphate to storage reservoirs for 

 the purpose of destroying algae, the possi- 

 bility of rendering such organisms more 

 resistant to the toxic effects of this sub- 

 stance suggests itself. Organisms of this 

 low type readily adapt themselves to en- 

 vironment and it is a conunon observation 

 among bacteriologists that an organism can 

 be made immune against the toxic effects 

 of an amount of substance which under 

 ordinary conditions would prove fatal to it. 

 This can be readily accomplished in the 

 laboratory by applying to such organisms 

 a subtoxic amount of germicide, and if the 

 experiment is repeated several times the 

 resistance of the organisms to that sub- 

 stance can be raised to a surprising degree. 



In discussing certain objections to the 

 use of copper sulphate in public water 

 supplies. Dr. AYiley has justly observed that 

 the zeal of certain poorly informed w^ater 

 superintendents will lead them to apply 

 more copper sulphate to the water than is 

 necessary for the pxirposes in view, and 

 thereby possibly increase the amount con- 

 tained in the water to a point at which it 

 would have an unfavorable effect upon the 

 consumers of that water. The reverse of 

 this is also true. It is no easy matter in 

 many cases to determine the amount of 

 water contained in a reservoir or pond, and 

 even the most careful measurements will 

 vary occasionally by fifty and sometimes 

 even one hundred per cent. Now if a water 

 superintendent like that mentioned by Dr. 

 Wiley should determine in his customary 

 arbitrary fashion the amount of water in 



a reservoir and apply to it a proportion of 

 copper sulphate, based upon his incorrect 

 estimate of the contents of the reservoir, 

 either more or less than is absolutely neces- 

 sary will be used, according to the error in 

 the estimate. Every time an insufficient 

 amount is applied it will undoubtedly have 

 the effect of raising the resistance of the 

 algfe to this germicide and there will come 

 a time when it will be impossible to exter- 

 minate them without the addition of a pro- 

 hibitive amount of the sulphate. 



Dr. ]\Ioore assumes that by the addition 

 of a proper amount of copper sulphate the 

 alga^ will be driven from a reservoir for all 

 time and states that up to the present time 

 in no case has the organism been found to 

 persist. There is, however, a notable case 

 in which a second application has been 

 necessary. The work was carried on by 

 one of the foremost water biologists of the 

 United States who has given long years of 

 study to the microorganisms which give 

 offense in public supply. In this case the 

 operator possessed an accurate knowledge 

 of the amount of water in the reservoir. 

 The water was infested with the organism 

 'Anah(ena.' One application conducted 

 according to Dr. IMoore's directions failed 

 to exterminate the organism and a second 

 treatment was applied which was effectual. 

 Almost immediately, however, the organism 

 ' Chlamydomonas,' which is in some re- 

 spects far more objectionable, developed in 

 the reservoir, flourishing apparently upon 

 the ' Anabana ' debris, the result being that 

 the conditions were far worse than those 

 which existed previous to the first applica- 

 tion of copper sulphate. This experiment 

 indicates that one application is not always 

 effectual and that an amount of copper 

 sulphate toxic for an ordinary alga may 

 not destroy the more lancommon varieties. 



These observations are cited merely for 

 suggestion. They do not by any means 

 dispute the value of the highly successful 



