Though it is not very probable that any part of a tax, which is not only imposed upon one of the most proper subjects of taxation, a mere luxury and superfluity, but which affords so very important a revenue as the tax upon silver, will ever be given up as long as it is possible to pay it; yet the same impossibility of paying it, which in 1736 made it necessary to reduce it from one-fifth to one-tenth, may in time make it necessary to reduce it still further; in the same manner as it made it necessary to reduce the tax upon gold to one-twentieth.

That the silver mines of Spanish America, like all other mines, become gradually more expensive in the working, on account of the greater depths at which it is necessary to carry on the works, and of the greater expense of drawing out the water and of supplying them with fresh