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theoretical considerations to conclude that the commercial value of a long sub-marine cable could be doubled if pure copper wire were substituted for the impure wire previously employed; for he showed that the speed of sending, or the number of words that could be sent per minute, was cæteris paribus inversely proportional to the specific resistance of the copper employed, and could not be increased by increasing the battery power. Consequently those who up to that time had looked on the systematic electric testing of copper wire as unnecessary had now become most strenuous in urging its regular adoption, so that at the present time no coil of copper wire was employed in a submarine cable which had not, by being previously tested, proved itself to have less than the contract resistance.
A number of specimens of Japanese copper wire, of different gauges, had recently been electrically tested in this way in Prof. Ayrton’s laboratory, and the result had been that, while many samples had as much as twenty or thirty per cent more resistance than pure copper and therefore would be quite valueless for submarine cable or telegraph instruments, other samples had scarcely more resistance than if they had been composed of pure copper, in a few cases, indeed, not even one per cent more. Consequently, as far as conduction was concerned, wire like the good samples would be of great practical value for telegraphic purposes. The price per pound of both bad and good samples was practically the same, and less, or at any rate not more, than the wholesale price in England of commercial copper wire.
Mr. Gowland, F.C.S of the Imperial Mint, Osaka, said that in reply to the remarks of the last speaker respecting the variable electro-couductivity of Japan copper, exceedingly high numbers having been obtained in some cases and low numbers in others, he would state briefly a few of the results to which he had been led by the chemical and physical examination and metallurgical treatment of about eight hundred tons of copper. The copper of Japan as a rule, when properly refined in a suitable furnace, was calculated to take a foremost place amongst the various kinds of commercial copper destined for electro-telegraphic or other purposes where special purity was essential. It was almost invariably free from the injurious metals antimony and arsenic as well as from phosphorus. Antimony he had never found excepting in traces, and arsenic when present rarely in larger quantities than .03 per cent. In fact when the crude copper was carefully selected and subjected to the Welsh process of refining, the resulting metal should consist of almost pure copper with traces only of lead, iron and silver. The importance of the purity of copper and of its special freedom from antimony, arsenic and phosphorus had been exhaustively treated by Matthieson in a paper communicated by him to the Royal Society and afterwards published in their “Transactions.” His results were obtained from experiments made upon impure, pure, and alloyed, specimens of copper the composition of which he had previously determined by chemical analysis. These results were opposed to some experimental