For many centuries[84] the Tin Mines in Cornwall have given to the country a very important place in the oeconomical history of nations, and furnished a perpetual source of employment to a very large population, which exclusive of the artisans, tradesmen, and merchants, cannot be estimated at less than sixty thousand persons. All the transactions connected with the Tin Mines are under the controul of the Stannary Laws. Courts are held every month, and they decide by juries of six persons, with a progressive appeal to the Lord Warden, and Lords of the Duke of Cornwall's council; no custom, however, or ancient law, prevails as to the working of Copper or Lead in the Stannaries, and therefore all agreements are made upon such terms as are decided on by the contracting parties. At present the greatest metallic product of the county is Copper,[85] although this metal is, comparatively of modern discovery, and has not been worked longer than a century. The reason assigned for its having so long remained concealed is the assumed fact, that Copper generally occurs at a much greater depth than Tin, and that, consequently, the ancients for want of proper machinery to drain off the water were compelled to relinquish the metallic vein before they reached the Copper; it is stated by Pryce, in his _Mineralogia Cornubiensis_, as a general rule, that Tin seldom continued rich and worth working lower than 50 fathoms; but of late years the richest Tin mines in Cornwall have been much deeper. _Trevenen Mine_ was 150,--_Hewas Downs_ 140,--_Poldice_ 120, and _Huel Vor_ is now upwards of 130 fathoms in depth. Upon the first discovery of Copper ore, the miner to whom its nature was entirely unknown, gave it the name of _Poder_; and it will hardly be credited in these times, when it is stated, that he regarded it not only as useless, but upon its appearance was actually induced to abandon the mine, the common expression upon such an occasion was, that "_the ore came in and spoilt the Tin_."[86] About the year 1735, Mr. Coster, a mineralogist of Bristol, observed this said _Poder_ among the heaps of rubbish, and seeing that the miners were wholly unacquainted with its value, he formed the design of converting it to his own advantage; he accordingly entered into a contract to purchase as much of it as could be supplied. The scheme succeeded, and Coster long continued to profit by Cornish ignorance.