334 SCIENCE PROGRESS 



a speck of electro-negative impurity on a brass surface by four 

 arrows at right angles pointing from four P's to a central N, 

 the diagram being followed by the statement : 



" If the impurity be a conductor of electricity the brass will 

 pass from the atomic to the ionic state by the displacement of 

 the hydrogen ions and consequently a moat will form round the 

 negative centre. If the impurity happen to be positive, it will 

 pass into solution with the production of a pit." 



After reading this, the marine engineer will surely feel that 

 the last word has been said on the subject and that what he 

 does not know of corrosion is not knowledge. 



I have written thus strongly, as I feel that it is important 

 that something should be done to stop the misappropriation of 

 ions in the service of corrosion and to emphasise the need of 

 clear thinking. I would plead also that some imagination, some 

 breadth of outlook, may be imported into the inquiry — and, 

 before all things, that a sense of logic should be cultivated by 

 those who essay to take part in the discussion. 



H. E. A. 



