1. _The exchange of goods by barter is extremely difficult in most cases._ Thus far we have not considered the subject of money and have so far as possible avoided even the use of the term. Value in economics does not depend on money, and is not necessarily connected with it. Things can be compared in their utility, their importance to our welfare can be estimated, without the use of money. Many problems of economics can be discussed pretty thoroughly and solved without the use of the word money or any term of similar meaning. But to-day it is impossible to go very far in the discussion of economic questions without using the concept of money, which is interwoven with every practical and theoretical problem in economics. We have delayed to the farthest limit the formal recognition of the subject; but we are now approaching the question of capital and interest, and it is no longer possible to avoid a preliminary consideration of the money concept. [Sidenote: Exact measurement of utilities is not possible without some medium of exchange] In considering the problem of exchange of consumption goods, we have assumed that it is possible to weigh small differences in the marginal utility of goods, and that such differences have influence on exchange. Now in exchange by barter such a small estimate is impossible. In barter things are exchanged directly for each other in kind. If the two things do not chance to coincide in value, the exchange cannot be completed. An equivalent must be found, or a multiple, if the marginal utility of two goods is to be equalized for either party by exchange. As in most cases this adjustment must be very incomplete, many exchanges that otherwise would be advantageous cannot take place. In the earlier stages of development, this careful estimate of value is not found. Children do not make it. The typical trade of the small boy is a "trade even"; Johnny exchanges his gingerbread for Jimmie's jack-knife. It marks an epoch in the industrial development of the boy when he begins to keep store with pins, and no longer trades candy for apples, but both for pins, which have become the medium of exchange in his boy world. He then can express values in much more exact terms. In our society most children begin early to grow familiar with this conception; but travelers find some savage tribes still in the earlier childish stage of development, unable to grasp the thought of a general medium of exchange. When, through lack of a medium of exchange, there is a failure to adjust utilities, there is a loss of the possible advantage in each defeated exchange. There is a further waste of time and of vain efforts to find something that will be accepted in exchange, and the loss offsets a large part of the gain even when the barter is effected. [Sidenote: Money is found to serve as a general medium of exchange]