ACTION OF WATER ON IRON. 289 



Without this precaution the present experiments, although 

 correct, would stand isolated, and be scarcely capable of being 

 even brought into comparison with future ones. Nor could it 

 be hereafter determined what change as to corrodibility, future, 

 and now perhaps unthought of, revolutions in the manufacture 

 of iron may produce in the metal to be made in years yet to 

 come. 



84. The writer's experiments also lead to the expectation, 

 that with the same bar of iron, or the same casting, a simple and 

 closely approximate estimate may be formed of its destructi- 

 bility in water or in solutions of the alkaline or earthy chlorides ; 

 by the rate of its solution in other agents ; and with this view 

 experiments are in progress upon the standard bar and other 

 iron, and in the event of their results being found as here stated, 

 it is obvious that upon the basis of the present prolonged ex- 

 periments in sea water, the durability, under similar circum- 

 stances, of all other or future irons may be determined in a few 

 hours by the aid of this new method of examination. 



85. The subject now leads us to consider briefly the various 

 modes of protection which have been proposed for the purpose 

 of preventing, as far as possible, those actions of water and air 

 on iron, the rate and nature of which our experiments have been 

 directed to determine ; and these, with the exception of mere 

 superficial coverings, as already alluded to, have all been of the 

 electro-chemical class, and more or less directly derived from 

 Sir Humphry Davy's original discovery and proposal of the 

 protection of the copper sheathing of vessels. In that paper the 

 great principle was developed of counteracting chemical by 

 electrical forces ; his successors have only, with greater or less 

 perfection, developed and applied his brilliant idea to particular 

 cases, while in doing so, it must be confessed, they have cor- 

 rected some small errors into which this great philosopher fell. 

 In Sir H. Davy's original papers on the preservation of copper 

 sheathing, he distinctly states, that it follows from his principles 

 then developed, that cast or wrought iron may be preserved 

 from chemical action by suitable protectors of zinc or tin. 



But my friend Professor Edmund Davy has unquestionably 

 the merit of having been the first to conduct a series of well- 

 devised and careful experiments upon the subject on the large 

 scale, which he did partly in connexion with the preservation 

 of the iron work of the mooring chains and buoys in Kingstown 

 harbour, under the auspices of the Board of Public Works. 

 The results of these have been already communicated by him to 

 the Association, at its meeting in Dublin, and published in its 

 reports. 



