592 Proceedings of the British Association. 



subjected to the influence of sea-water in harbours, as at Kings- 

 town ; where it was recently found that the rings, upon which 

 the safety and utility of the buoys mainly depend, rapidly cor- 

 rode and are destroyed. Mr Davy turned his attention to the 

 important object of providing a remedy, and preventing the cor- 

 rosion of the iron ; and although his experiments had only re- 

 cently been commenced, still he considered it proper to bring 

 the few results he had procured before the Section, for the pur- 

 pose of exciting further inquiry. He found that zinc applied 

 to iron prevented corrosion. Rings of this metal were cast into 

 forelocks for the purpose of experiment, and were found to ob- 

 viate the waste to which the iron had previously been subject. 

 According to Sir Humphry Davy, the cause of the corrosion of 

 copper and metals in contact with sea water, is attributable to 

 the access of atmospheric air. He considered that if the air was 

 preserved from coming in contact with the metal, no decomposi- 

 tion would ensue. Mr Davy accordingly found, that copper 

 exposed to the action of sea water, free from the influence of 

 air, was not liable to corrosion, and that the effect was influ- 

 enced by the depth of water. Specimens of metals were exhi- 

 bited, which had been subjected to the influence of salt water 

 free from air, and no corrosion had taken place ; other pieces of 

 metal which were in contact with sea water, subject to the influ- 

 ence of air, were observed to be much injured. Mr Davy at- 

 tributed the cause of the phenomenon to an electrical decompo- 

 sition. He stated further, that he had found zinc to preserve 

 tin-plate, both in fresh and salt water. Some observations were 

 made by members of the Section with regard to the action of 

 sea water upon bar and cast iron. Some attributed the great - 

 est corrosion to the former, others to the latter. 



2. Mr Ettrick described an improvement which he had made 

 upon Davy's safety-lamp, for the purpose of obviating accidents 

 which are entirely owing to the carelessness of workmen. The 

 Davy lamp, he stated to be perfect in principle. The work- 

 men arc in the habit of enlarging the apertures in the wire 

 gauze, and applying their tobacco pipes in order to obtain a 

 light. The modifications recommended at present were, the in- 

 troduction of very strong glass, to cover the gauze externally. 



