196 Proceedings of the British Association for [Sept. 



buoys, subjected to the influence of sea water in harbours, 

 as at Kingstown ; where it has been recently found, that the 

 rings upon which the safety and utility of the buoys mainly 

 depend, rapidly corrode and are destroyed. Mr. Davy 

 turned his attention to the important object of providing a 

 remedy, and preventing the corrosion of the iron ; and al- 

 though his experiments had only recently been commenced, 

 still he considered it proper, to bring the few results he had 

 procured before the Section, for the purpose of exciting 

 further inquiry. He found that zinc applied to iron pre- 

 vented corrosion. Rings of this metal were cast into fore- 

 locks for the purpose of experiment, and were found to 

 obviate the waste to which the iron had previously been 

 subject. 



According to Sir Humphry Davy, the cause of the corro- 

 sion of copper, and metals in contact with sea water, is 

 attributable to the access of atmospheric air. He con- 

 sidered that if the air was preserved from coming in contact 

 with the metal, no decomposition 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 cor- 

 rosion, and that the effect was influenced by the depth of 

 water. Specimens of metals were exhibited, 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 influence of 

 air, were observed to be much injured. Mr. Davy attributed 

 the cause of the phenomenon to an electrical decomposition. 



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 greatest 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 workmen are 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 



