A careful study of the subject by Professor Rogers shows that early in the thirteenth century one pound of gold was worth ten pounds of silver, at the close of that century would buy twelve and one-half pounds of silver, and in the middle of the fourteenth century bought thirteen and three-fourths pounds; but in the fifteenth and sixteenth centuries, after the new world was pillaged, one pound of gold bought from ten and one-half to twelve pounds of silver. In the seventeenth century fifteen pounds of silver went for one pound of gold, and in the eighteenth, fifteen and one-half pounds. Early in the nineteenth century the ratio was fixed in this country at sixteen of silver to one of gold, and that estimate was assumed to be essentially correct as late as 1877, when a pound of gold would exchange in the market for three and one-half pounds of platinum, seven pounds of aluminum, sixteen pounds of silver, seventy-one pounds of nickel, 942 pounds of tin, 1,696 pounds of copper. Twenty years have produced great changes in both the total annual products and the relative cost of mining. The estimate of 1877 would now be incorrect for any of the metals named. A pound of gold now buys 1,540 pounds of aluminum, the change being due to an invention for reducing aluminum ore. It now takes about thirty-seven pounds of silver to pay for one pound of gold, a change in part due to new systems of coinage in which silver plays a subordinate part, but chiefly due to the greatly increased product of rich mines and greatly improved methods of reducing ores. _The cheaper money drives out the good money._—In any system of coinage, employing both silver and gold as standards, it is found by actual experience, repeated hundreds of times, that a change in the ratio between the two metals in open market always leads to hoarding for speculative purposes of the most costly metal of the two.