Section of Chemistry and Electricity, 391 



work at the bottom of each buoy, two zinc protectors, each of which 

 is about 6 inches long and 4 inch wide, and weighs about 8 ounces; 

 and on a recent examination, the iron-work near the zinc exhibited 

 a clean appearance. There is another and a still more recent ap- 

 plication of the zinc, which the author thinks will be very beneficial 

 in protecting a most important part of the iron-work already alluded 

 to, namely, the forelock. Several of the forelocks have stout zinc 

 rings cast into holes made in their heads, and on lately examining a 

 forelock so protected for several weeks, it was found quite free from 

 corrosion. 



The late Sir H. Davy referred the corrosion of copper in sea- 

 water to the agency of the oxygen of the air. The author from his 

 experiments has obtained results which lead to the same conclusion 

 with regard to iron. He found also that the corrosion of iron in 

 sea-water is materially influenced by the depth of water in which 

 the metal is immersed. He is of opinion that the wear of iron-work 

 exposed to sea-water is more considerable the nearer the iron is to 

 the surface or to the external air. The principal wear of the iron- 

 work connected with the buoys seems to be at and within a few feet 

 of the surface of the water ; and this portion of the iron may be 

 protected by attaching strong pieces of zinc to it. 



The corrosion of iron in sea-water, under ordinary circumstances, 

 appears to arise from exposure of the water to the atmosphere, and 

 the consequent gradual absorption of its oxygenous part. The 

 protection of iron in sea- water by the contact of zinc seems due to 

 a simple electrical action between the respective metals and the 

 fluid ; water being decomposed, its hydrogen is evolved, its oxy- 

 gen goes to the zinc, whilst the oxide of zinc as it forms seems to 

 be deposited on the iron, at least in part. 



The author made a number of experiments to ascertain whether 

 zinc would protect iron in sea-water if a very thin surface of glass, 

 wood, paper, tow, &c. were severally interposed between those me- 

 tals, but the results seemed clearly to prove that actual contact of 

 the metals is indispensably necessary to that effect. 



Zinc will protect iron in fresh water. The author has made ex- 

 periments on this subject, and has others still in progress ; the re- 

 sults of which may admit of useful applications to valuable parts of 

 machinery, &c. 



The author expressed his obligations to Mr. Hutcheson, the Har- 

 bour-Master at Kingstown, for the kind and prompt assistance 

 he afforded on every occasion, and for the interest he took in the 

 progress of the experiments on the buoys, &c. 



On some recent Experiments made with a view to protect Tin Plate 

 or tinned Iron from corrosion in Sea-water, with some probable ap- 

 plications ; and on the power of Zinc to protect other Metals from 

 corrosion in the Atmosphere. By Edmund Davy, F.R.S., 

 M.R.I. A., fyc, Professor of Chemistry to the Royal Dublin So- 

 ciety. 

 If a piece of tin plate is exposed in sea-water for a few days, it 



