Journal . thcoming. A small number of these failures may be attributedto inaccuracy in mathematical calculations ;. again, we mayreasonably expect steel, when subjected to more or less sys-tematic periodic vibrations, , on locomotive trucks or motorcars, occasionally to develop lines of intercrystalline weaknessand fracture, but undoubtedly one of the most prolific causes ofaccident is attack by rusting and corrosion. The microphotograph kindly taken by Mr. E. Law is a sectionof a tie-rod that failed in Charing Cross railway station. Thesituation was one very conducive to corrosion, since
Journal . thcoming. A small number of these failures may be attributedto inaccuracy in mathematical calculations ;. again, we mayreasonably expect steel, when subjected to more or less sys-tematic periodic vibrations, , on locomotive trucks or motorcars, occasionally to develop lines of intercrystalline weaknessand fracture, but undoubtedly one of the most prolific causes ofaccident is attack by rusting and corrosion. The microphotograph kindly taken by Mr. E. Law is a sectionof a tie-rod that failed in Charing Cross railway station. Thesituation was one very conducive to corrosion, since the moisturedeposited on the cold surfaces of the metal was highly chargedwith the sulphur acids of burning coal. It will be seen thatpractically three-quarters of the metal has been corroded away,owing to the absence of a suitable protective surface. Although the phenomenon of rusting has been observed andnoted from times immemorial, it is only comparatively recently 240 THE CORROSION AND RUSTING OF FlO. 1. that a systematic investigation of the various factors that go tomake up the process has been attempted. Chemically, rust is ofvery complex and variable composition, consisting of hydratedoxides of iron, basic ferric carbonate, organic matter, and fre-quently fixed sulphur, phosphates and silicates. Many theories have been advanced to explain the mechanismof iron corrosion, and in the authors opinion at least, the so-calledelectrolytic theory advanced in America by Whitney, Cushmanand WTiipple, and in England by Tilden, Walker and Lambert andothers, is by far the most convincing. We may regard all metalsas exhibiting definite tendencies to go into solution even in purewater. The magnitude of this solution-tendency depends ontwo factors (i.) the nature of the metal—zinc, for example, pos-sesses a very high, and platinum a very low solution-tendency,and (ii.) the composition of the solvent, , copper possesses ahigh solution-tendency in ammoniacal solutions and a
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