606 



SCIENCE. 



[N. S. Vol. XXI. No. 538. 



color and only a slight odor and taste were 

 noticeable on the surface. On Sunday, 

 July 24, the water in the reservoir, being 

 absolutely pure, for the first time in ten 

 years, during the summer months, was 

 turned into the city mains, and since this 

 date has been in constant use. 



Many other examples might be given of 

 the efficiency of copper sulphate as a pre- 

 ventative of algal pollution, but it is prob- 

 ably sufficient to say that over fifty large 

 water supplies have been successfully treat- 

 ed during the last six months, and in no 

 instance where a supply was in actual use 

 and the method applied according to direc- 

 tions has it failed to accomplish the desired 

 result. 



It is not necessary to dwell upon the 

 question of cost. In general this may vary 

 from ten cents to fifty cents per million 

 gallons, and no water company is likely to 

 hesitate at this amount if it enables them 

 to get rid of a difficulty which often causes 

 them an annual expense of thousands of 

 dollars, to say nothing of the complaints 

 of consumers. 



The fact that copper has been used in a 

 number of water supplies in quantities of 

 from one to a million to one to ten or'fifteen 

 millions without causing any perceptible 

 difficulty might be regarded as evidence in 

 favor of the harmlessness of copper to man, 

 or at least as demonstrating that this metal 

 is not poisonous in the generally accepted 

 sense of the word. There is, however, a 

 deep-seated prejudice against copper in the 

 popular mind, and it is difficult to convince 

 the public that the eases of poisoning sup- 

 posed to have been due to eating food from 

 copper utensils were due to other causes, 

 now well recognized. Perhaps there will 

 always be a certain amount of opposition to 

 the use of copper, just as there is to anti- 

 toxin and vaccination. After all, the ques- 

 tion is a local one which must be decided by 

 the local authorities, and if there is any 



question about the method it should not be 

 resorted to. Certainly, the Department of 

 Agriculture does not wish to insist upon 

 the use of copper sulphate without the 

 hearty consent of the authorities who have 

 the control of the water supply, and this 

 consent has always been obtained before 

 any work of this kind has been carried on. 



The fact that we daily consume in our 

 food quite as much, if not more copper, 

 than would ever be added to a water supply 

 is not generally known by the public; not 

 only in peas and other canned goods, where 

 copper has been added for a purpose, but 

 in meats, fruits, vegetables, etc., w^here this 

 metal occurs naturally. There is often five 

 times as much copper in a pound of wheat 

 as would ever be found in a gallon of water 

 treated for the destruction of algae. But 

 there is so much evidence in favor of the 

 harmlessness of copper that it is impossible 

 to even refer to it here. After all, it should 

 be borne in mind that it is not a question 

 of an absolutely pure water as compared 

 with water containing a small amount of 

 copper. It is typhoid- or cholera- or algae- 

 laden water versiis copper water. 



When the efficiency of copper for the 

 destruction of algas had been fuUy demon- 

 strated, it became a matter of interest, at 

 least, to determine the eifect of this metal 

 upon typhoid, cholera and similar disease 

 germs often conveyed by water. As the 

 result of a large number of experiments we 

 were able to determine that while copper 

 was not quite so toxic to these pathogenic 

 bacteria as to algae, still the r.esTilts were 

 sufficiently satisfactory to make it seem 

 probable that, under certain circumstances, 

 the method might prove of considerable 

 value for the rapid and efficient steriliza- 

 tion of large bodies of water. 



The conditions governing pollution by 

 algffi and bacteria are, of course, very dif- 

 ferent. 'Furthermore, there are methods 

 already in use, which, if properly applied, 



