But though the judgment of sober reason and experience concerning such projects has always been extremely unfavourable, that of human avidity has commonly been quite otherwise. The same passion which has suggested to so many people the absurd idea of the philosopher’s stone, has suggested to others the equally absurd one of immense rich mines of gold and silver. They did not consider that the value of those metals has, in all ages and nations, arisen chiefly from their scarcity, and that their scarcity has arisen from the very small quantities of them which nature has anywhere deposited in one place, from the hard and intractable substances with which she has almost everywhere surrounded those small quantities, and consequently from the labour and expense which are everywhere necessary in order to penetrate to and get at them.