1826.] Preservationof Metals by Electro-chemical Means. 257 



have been adhesions, at least in Portsmouth or Sheerness har- 

 bours, where the water is constantly muddy, and where the 

 smallest irregularity or roughness of surface, from either wear, 

 or the deposition of calcareous matter, or the formation of oxides 

 or carbonates, enable the solid matter floating in the water to 

 rest. There is a ship, the Howe, one of the largest in the Navy, 

 now lying at Sheerness, which was protected by a quantity of 

 cast iron judged sufficient to save all her copper, nearly fifteen 

 months ago. She has not been examined ; but I expect and 

 hope that the bottom will be covered with adhesions, which 

 must be the case if her copper is not corroded ; but notwith- 

 standing this, whenever she is wanted for sea, it will only be 

 necessary to put her into dock for a day or two, scrape her 

 copper, and wash it with a small quantity of acidulous water, 

 and she will be in the same state as if newly coppered. 



At Liverpool, as 1 am informed, several ships have been pro- 

 tected, and have returned after voyages to the West Indies, and 

 even to the East Indies. The proportion of protecting metal in 

 all of them has been beyond what I have recommended, ~ to 

 •^-g- ; yet two of them have been found perfectly clean, and with 

 the copper untouched after voyages to Demerara ; and another 

 nearly in the same state, after two voyages to the same place. 

 Two others have had their bottoms more or less covered with 

 barnacles ; but the preservation of the copper has been in all 

 cases judged complete. The iron has been placed along the 

 keel on both sides ; and the barnacles, in cases where they have 

 existed, have been generally upon the flat of the bottom ; from 

 which it may be concluded, that they adhered either to the . 

 oxide of iron, or the calcareous deposits occasioned by the excess 

 of negative elei'tricity. 



In the navy the proportion adopted has been only ^^4-^ of cast 

 iron, at least for vessels in actual service, and when the object 

 is more cleanness than the preservation of the copper. 



It is very difficult to point out the circumstances which have 

 rendered results, such as these mentioned with respect to Liver- 

 pool traders, so different under apparently the same circum- 

 stances, i. e. why ships should exhibit no adhesions or barnacles 

 after two voyages, whilst on another ship, with the same quan- 

 tity of protection, they should be found after a single voyage.* 

 This may probably depend upon one ship having remained at 

 rest in harbour longer than another, or having been becalmed 

 fc>r a short lime in shallow seas, where ova of shell fish, or young 

 shell fish existed ; or upon oxide of iron being formed, and not 

 washed off, in consequence of calm weather, and which consoli- 

 dating, was not afterwards separated in the voyage. From 



* The quality of the copper may be ttnother cause. 

 New Series, vol. xi. s 



