250 ANNUAL OF SCIENTIFIC DISCOVERY. 



our experiments under the same condition, or have a thorough understanding 

 of how to apply the results got from single sheets to the conditions to which 

 these may be applied, such as the clear conceptions which characterize Sir H. 

 Davy's inquiry, and from which I have no hesitation in saying, that were a 

 ship sheathed with a mixture of all these coppers given in Capt. James' 

 experiments, the few sheets of alloy of copper and phosphorus would induce 

 a rapid waste of the whole, and to analyse those sheets destroyed first and 

 those wearing best, we would have the conclusion that impure copper is best 

 for sheathing. To test this deduction ~by experiment, I alloyed samples of the 

 same quality of copper with two per cent, of metal of the different sorts 

 referred to in the following table, had the samples beaten into small plates, 

 and submitted them to the action of the sea in Lamlash Bay, Arran, for four 

 weeks. At the termination of the experiment, the appearance of each speci- 

 men was worthy remark ; some were coated over with a light green patina, 

 others had become light and brassy looking, and some had a reddish brown 

 color, much like that described as the appearance of sheathing that has worn 

 ill. The quantity of loss on the square foot of surface exposed to the action 

 of the water was then taken with the following results : 



Copper without alloy lost 14-1 grains 



" with Bismuth 133 " 



" " Lead 181 



" ' Antimony Ill " 



" " Tin 98 " 



" " Silver 65-5 " 



" " Cobalt 62 " 



" " Nickel 58 " 



" " Iron 50-5 " 



In these experiments we observe that pure or unalloyed copper is more 

 rapidly acted upon in sea water than copper having a little alloy ; but the 

 next question was, how sheets of any of these coming into contact with pure 

 copper, would affect the wear of the pure copper by a galvanic influence. I 

 therefore took a small sheet of equal size of pure copper, and connected each 

 with one of those alloyed pieces, and submitted them to the action of sea water 

 (but in this instance it was artificial sea water made by dissolving the differ- 

 ent ingredients according to the analysis given for the English Channel). The 

 water was stirred several times every day, and the experiment was continued 

 for twenty-seven days. Only the loss upon the pure copper was taken. I 

 regretted that the weight of the alloyed pieces was not also taken ; however, 

 the following was the result of the experiment given upon one square foot of 

 surface exposed: 



Pure copper, with the cobalt alloy 197-7 grains. 



" " arsenic alloy 191-3 " 



" " nickel alloy 179-2 " 



" " antimony alloy 174'0 " 



" " bismuth alloy 169-0 " 



" " silver alloy 165-1 



" " iron alloy 153-4 " 



" " lead alloy 152-3 " 



" " tin alloy 152'0 " 



Pure copper alone 148-7 " 



