If, for instance, I want a telescope, in exchange for a book, I shall probably have to make many inquiries, and to wait a long time before I meet with a person who has a telescope to spare, and who is also willing to take my book in exchange. It is very unlikely that he who has a telescope will just happen to want that particular book. A second difficulty is, that the book will probably not be worth just as much as the telescope, and neither more nor less. He who owns a valuable telescope cannot cut it up, and sell a part to one and a part to another; this would destroy its value. #77. Convenience of Money.# With the aid of money all the difficulties of barter disappear; for #money consists of some commodity which all people in the country are willing to receive in exchange, and which can be divided into quantities of any amount#. Almost any commodity might be used as money in the absence of a better material. In agricultural countries corn was so used in former times. Every farmer had a stock of corn in his own granary, and if he wanted to buy a horse or cart, he took so many sacks of corn to his neighbour's granary in exchange. Now suppose that, with corn as money, a farmer wanted to part with a cart and get a plough instead; he need not inquire until he finds a person willing to receive a cart, and give a plough in exchange. It is sufficient if he find one farmer who will receive a cart and give corn, and any other farmer who will give a plough and receive corn. No difficulty arises, too, if the cart or plough are not of equal value; for if the cart be the more valuable, then the farmer finally gets for it the plough together with enough corn to make up the difference. Money thus acts as a #medium of exchange#; it is a go-between, or third term, and it facilitates exchange by dividing the act of barter into two acts, in this way-- #Sale.# #Purchase.# _____/\______ ____/\____ / \ / \ #Cart.# #Money.# #Plough.# No doubt it turns one act of exchange into two; but the two are far more easy to manage than one, because they need not be made with the same person.