3 i2 SCIENCE PROGRESS 



outside mere haphazard discovery — which has often been 

 attended with the most important results— hypotheses are of 

 infinite service to the inquirer, that there can be no rational 

 inquiry without some hypothesis ; yet the modern tendency 

 to strain each particular hypothesis to the utmost limit and 

 to confine attention to it alone, is to be deprecated on many 

 grounds, especially because it so limits the ambit of experi- 

 mental inquiry. 



The recent May meeting of the Iron and Steel Institute, 

 held since the previous section of this article was written, 

 brought forth the now usual crop of papers on the corrosion 

 of iron. In the interval a valuable work on the subject by 

 Dr. Friend has also been published ; in this he not only de- 

 scribes his own experiments but also summarises the very 

 large number of observations that have been placed on re- 

 cord by various workers. It will be only too obvious to those 

 who study this work and the papers referred to (p. 323) that 

 the whole subject is still shrouded in a deplorable obscurity. 



In point of fact, the subject of the corrosion of metals 

 not only teems with unsolved problems but is one in which 

 clear thinking is required, so that the fundamental issues may 

 be rendered obvious and experiments instituted on proper lines. 



At the outset we may write C = E/R, the well-known formula 

 of the electrician — Ohm's law — as expressing the facts. In the 

 case of any change, the amount of chemical change and there- 

 fore the electrical current, C, is proportional to the electrical 

 pressure or chemical efficiency developed in the electrolytic 

 circuit within which the change takes place and inversely pro- 

 portional to the electrical resistance in the circuit. This 

 statement by implication involves the acceptance of the view 

 that the conditions which obtain in a voltaic cell are those 

 that must be fulfilled if action is to take place. If it were 

 generally taught that such an expression governs every change, 

 some progress towards an understanding would be made. But 

 it is not one of the articles of physical-chemical belief commonly 

 promulgated : it is never put forward in the text-books— 

 indeed, interactions are only too often spoken of as either 

 chemical or electrical, as if it were possible to draw a distinc- 

 tion between the two kinds of change. As I have frequently 

 taken occasion to point out, no heed whatever is paid in 



