868 TsAysACTioys of the American Institute. 



on the corrosion of man}' kinds of iron exposed to the common 

 and foul atmospheres, to clear, foul, acidulated and salt waters, and 

 came to the following general conclusions: 



That iron exposed to water holding air in combination, corrodes 

 on the surface, either uniformly, or in places, by rust, or by con- 

 vei*sion into plumbago, and that the corrosion depends upon the 

 want of homogeneousness of the surface, or in its denseness, hard- 

 ness, or the combination of the carbon with the metallic iron. 



This subject was under discussion at the London Institution of 

 Civil Engineers in 1862, and some of the most eminent engineers 

 there, joined in the discussion. It is probabl}' the most complete 

 examination of the question that had up to that time been made, 

 and the numerous cases which were cited, both of the corrosion 

 and of its absence, in iron under water, and the causes, seem to 

 leave but little more to be said on the subject. 



Three of the iron gates at Sheerness, have resisted the action of 

 salt water for fort}'^ years uninjured, and in the fourth one, the 

 lower segment has become softened in less time, caused by contact 

 with a lead facing, producing a galvanic action. Similar gates at 

 Pembroke, of more than half the same age, are in perfect preser- 

 vation. 



Mr. Cabitt drove cast-iron piles at Lowestoft in 1834, which 

 were, in 1862, as sound and perfect as when driven. 



Mr. Simpson had previousl}^ carefully examined the question, 

 and by selecting the iron for the piles of the southern pier, driven 

 in 1844, found them eighteen years after in a perfect state. " The 

 square angles were as sharp as when they left the foundery." He 

 stated that the durability of cast-iron in salt water, depended 

 entirely upon its quality. In the Heine bay pier, built by Telford, 

 on wooden piles, and renewed in 1838, with cast-iron piles, the 

 latter were now perfectly uninjured. "The angles were as sharp 

 as when they left the foundery; not a shilling has been expended 

 for repairs upon them." " Some of the cast-iron piles, used for 

 the Margate jetty in 1831, were taken up twenty-two years after- 

 wards, and were sold at the same price as pig iron. On careful 

 examination, they were as sound as when they left the foundery, 

 and in no instance can any softening be detected, while some of 

 the original piles still in place, after standing thirty -one years in 

 the sea, show no evidence of the slightest deterioration." 



Other numerous cases can be cited of the duration of cast-iron 

 in soawater, which show no effects after an immersion of a quai'ter 



