_Diminishing cost of transportation._—That the cost of transportation keeps diminishing in spite of combinations of capital to prevent it, and in spite of local legislation restricting it, proves that the increasing perfection of machinery and the accession of capital in railroads and waterways are stronger than the purposes of men. That freights are regulated by “what the traffic will bear” is merely another way of saying that transportation comes under the universal law of values—what the service is worth in the market, or what people are willing to give for it. According to good authority, the net profit of carrying one ton of freight one mile has fallen in twenty-five years from one cent to less than one-ninth of a cent. The same principle fixes a classification of freight according to service. We can afford to pay more for carrying valuable produce than for carrying cheaper products. It also leads to special rates for developing traffic, as illustrated in rates on baled alfalfa hay from western plains to Chicago. Wise managers, if not misled by speculation in stocks, care more for enlarging traffic than for immediate returns upon a smaller bulk, because the bulk of profit is greater. A good illustration of development of a special traffic is found in the milk trains running two hundred or three hundred miles to supply the city of New York. The railroads are compelled by the needs of the traffic to carry the milk cheaply enough to prevent its being made into butter and cheese. Laws regulating this charge are effective, because such a necessity exists in the nature of the case. _Weights and measures._—Another important growth in the machinery of trade is found in standards of quantity,—weights and measures of every kind. It is scarcely possible to realize the uncertainty of exchange without exact weights and measures. The story of the Indian trader who bought furs by weight, putting his hand upon the scales for one weight and his foot for its double, illustrates how uncertain such judgments of quantity may be without system. The present names of weights and measures indicate their origin in similar ways. Measures have usually been connected with some part of the body: as “finger,” used one way in measuring the load of a gun and another on a stocking; “hand,” still used in measuring the height of horses; “span,” once considered sufficiently definite for any measurement; “foot,” now made to conform to an accurate system; and “pace,” still used in many communities. Connected with the arm, are “cubit” and “yard.” Many ladies still measure their dress goods by arm’s lengths. For small measures, “grain” and “barley-corn,” still used as names, indicate dependence upon average quantity in articles of general growth.