242 MODERN SCIENCE READER 



form is chlorine. Chloroform, which has been of such 

 inestimable value as an alleviator of pain, cannot be manu- 

 factured without chlorine, and it could never have been 

 discovered without the previous discovery of chlorine. 



Finally, without attempting to give a full account of all 

 the uses to which chlorine has been and is put for our 

 benefit, let me mention one more application, though in 

 doing so I may run the risk of leading some of you to the 

 conclusion that chlorine has its dark side as well as its 

 light. It is with some misgivings that I venture to tell 

 you that chlorine has found extensive application in the 

 extraction of gold from its ores, and as gold is held by some 

 to be the root of all evil, chlorine must, by the same token, 

 be regarded as particeps criminis. A few years ago I 

 visited the gold mines in the Black Hills of South Dakota, 

 and there I spent some time in examining the chlorination 

 process. I could not help thinking of Scheele and his 

 simple experiments that first brought chlorine to light. 

 I wondered whether, if he could see the extensive applica- 

 tions of that greenish-yellow gas that first set him to weep- 

 ing and coughing I wondered whether his satisfaction in 

 his work would be any greater than it must have been when 

 the discovery was made. Compare the little room in the 

 apothecary shop, the simple apparatus, and the apparent 

 uselessness of the noxious gas with the great factories, the 

 complicated machinery and the valuable applications al- 

 ready mentioned, and it is evident that a discovery that 

 appears least promising from the practical point of view 

 may be the beginning of the most valuable industries. 



Before leaving this part of my subject let me take a 

 much less important example than those already spoken of, 

 but one that comes nearer home. Nearly twenty-five years 

 ago in the laboratory under my charge, an investigation 

 was being carried on that seemed as little likely to lead to 

 practical results as any that could well be imagined. It 

 would be quite out of the question to explain what we were 

 trying to do. Any practical man would unhesitatingly 



