The portability of money is an important quality not merely because it enables the owner to carry small sums in the pocket without trouble, but because large sums can be transferred from place to place, or from continent to continent, at little cost. The result is to secure an approximate uniformity in the value of money in all parts of the world. A substance which is very heavy and bulky in proportion to value, like corn or coal, may be very scarce in one place and over-abundant in another; yet the supply and demand cannot be equalised without great expense in carriage. The cost of conveying gold or silver from London to Paris, including insurance, is only about four-tenths of one per cent.; and between the most distant parts of the world it does not exceed from 2 to 3 per cent. Substances may be too valuable as well as too cheap, so that for ordinary transactions it would be necessary to call in the aid of the microscope and the chemical balance. Diamonds, apart from other objections, would be far too valuable for small transactions. The value of such stones is said to vary as the square of the weight, so that we cannot institute any exact comparison with metals of which the value is simply proportional to the weight. But taking a one-carat diamond (four grains) as worth L15, we find it is, weight for weight, 460 times as valuable as gold. There are several rare metals, such as iridium and osmium, which would likewise be far too valuable to circulate. Even gold and silver are too costly for small currency. A silver penny now weighs 7-1/4 grains, and a gold penny would weigh only half a grain. The pretty octagonal quarter-dollar tokens circulated in California are the smallest gold coins I have seen, weighing less than four grains each, and are so thin that they can almost be blown away. 3. INDESTRUCTIBILITY If it is to be passed about in trade, and kept in reserve, money must not be subject to easy deterioration or loss. It must not evaporate like alcohol, nor putrefy like animal substances, nor decay like wood, nor rust like iron. Destructible articles, such as eggs, dried codfish, cattle, or oil, have certainly been used as currency; but what is treated as money one day must soon afterwards be eaten up. Thus a large stock of such perishable commodities cannot be kept on hand, and their value must be very variable. The several kinds of corn are less subject to this objection, since, when well dried at first, they suffer no appreciable deterioration for several years. 4. HOMOGENEITY