168 Mr. Napier on Cupper Sheathing. 



copper, but such information is not to be had, except by a detailed history 

 of all the operations of smelting during the last eighty years. 



Having thus briefly given an outline of the present state of our know- 

 ledge of the important question of copper sheathing, I will now call the 

 attention of the Society for a short time to my own views of the matter, 

 or rather to a vindication of the principle upon which Sir H. Davy based 

 his opinion, namely, that pure copper, and uniformity of composition and 

 character, are what are required for good sheathing, referring at the same 

 time to some of those prominent changes which have taken place in the 

 production of the copper, to cause the great deterioration recently so 

 much complained of. 



That old sheathing, such as that in use last century, is superior to that 

 of this century, especially to that made within these last twenty-five years, 

 is a fact generally admitted. Is, then, the cause of this difference due to 

 the quality of the metal ? In the absence of chemical analyses of old 

 sheathing, I have sought out probable proof iu respect to its quality in 

 the source from which the copper was obtained. Dr. Black, in his che- 

 mical lectures (vol. ii. p. 647) says, " Anglesea contains the richest bed 

 of copper perhaps in the world, and of late years yields about 25,000 

 tons of metal annually. The vein is about seventy feet thick." 



These mines were discovered about the time sheathing was introduced 

 into the navy, and it is computed that for many years not less than 

 80,000 tons of ore were extracted annually, and the copper commanded 

 the market of the world. Now the copper from these mines has always 

 been, as it still is, although the quantities now got are very small, the 

 best and purest in quality, and entirely free from those impurities which 

 I consider deteriorates the copper of this century. Towards the close of 

 last century, these mines became poorer, and have gradually declined; 

 the ores from Cornwall and other sources have increased, but the Cornish 

 ores do not yield copper of the same purity as the Anglesea ores. The 

 produce of the Cornish mines from 1800 to 1880 was more than doubled 

 — that of 1800 being 5,187, and that of 1830, 11,554 tons, but consider- 

 able importations of good copper ore were made from Russia, and assisted 

 to take the place of the declining supply of the Anglesea ores. 



In so far, then, as these ores varied in quantity and quality, so would 

 be the relative deterioration of the metal ; but it was more than relative as 

 regards the sheathing, for the superior quality of Pary's mine, and Russian 

 copper, caused it to be used either wholly, or mixed with the best Cornish 

 for hammered and other particular work, throwing the burden of the 

 inferior copper into sheets, as a lower quality of copper will roll better 

 than it will hammer. 



Mr. Prideaux, to whose papers I am indebted for many valuable practical 

 hints, asks, in one of his inquiries respecting the mixture of the ores for 

 smelting, " Were these mixtures not modified to suit the rich American 

 ores, when these were introduced, from which period some of the best 

 informed persons date the most rapid sea waste in the sheathing?" 



