Mr. Nai'IER on Copper Sheatliivg. 1*57 



sheathed with a mixture of all these coppers given in Captain James' 

 experiments, that the few sheets of Dr. Percy's alloy of copper and phos- 

 phorus would induce a rapid waste of the whole, and to analyse those 

 sheets destroyed first and those wearing best, we should have the conclu- 

 sion that impure copper is best for sheathing. 



Mr. Prideaux, whose long experience in the matter under discussion 

 deserves deference, seems almost inclined to abandon the quality of the 

 metal, and seek the cause wholly in the conditions, which he states thus: — 



1st. Friction from heavy shore work, faster sailing and more active 

 service. 



2d. Corrosive waters, as the drainage of mines, manufactures, sewers, 

 and putrescent matters in the sea. 



3d. Climate — corrosive action being increased by heat, and sheathing 

 is known to waste quicker in tropical climates. 



4th. Weather. — Electrical and thundery, storms, &c. 



5th. Electro-chemical. — Nails and metal giving a positive tendency to 

 waste. 



6th. Matters laid under slieaihing — as tar, paper, felt, which may have 

 acid or alkaline properties. 



7th. Timber of the vessel — some wood having acid properties, &c. 



Some of these seem as catching at straws, while others, as already 

 referred to, are important. Sir H. Davy found, that on a vessel going 

 at a speed of eight miles an hour, the copper most exposed to the friction 

 of the sea lost more than double that which was least exposed ; and Mr. 

 Prideaux found that pieces of the same quality of copper put into sea 

 water from dififerent localities, were differently acted upon. In thirteen 

 days' exposure the waste of copper in water from 



Heart of Gulf stream was 1*81 



Caribbean Sea 0'40 



Plymouth harbour 0'3l 



Such circumstances as these are easily defined; but the circumstances, that 

 when two vessels arc sheathed at one time, and kept nearlyunder the same 

 conditions, the copper of the one lasting two or three times that of the 

 other, or even one vessel, her sheathing at one time lasting seventeen or 

 twenty years, and at another not more than three or four, and employed 

 on the same service, are not so easily accounted for, and require a 

 more strict investigation. 



Mr. P. sums up his inquiry with the following : — " To whatever extent 

 the recently increased waste of sheathing may be due, such as constant 

 employ, muoh greater velocity, &c., there is reason to fear the fault is 

 Btill to be sought too often in the copper itself." These views induced 

 him to seek information, in a series of letters to the Mining Journal, to 

 find if any modification or change had taken place in the smelting of the 

 ores, so that it might lead to the cause of the increased deterioration of the 



Vol. III.— No. 3. 3 



