Sec. 9] INCOME SUMMATION 159 are sold. The dealer credits his stock of goods and debits his “cash,” while the buyer does the opposite. Stock of Goods Stock of Cash Seller. +. iced ert ausnalts +.§2 — $2 Buyer a — $2 + $2 The two transfers into which any exchange may be resolved are represented by the two columns of the table. But an exchange may also be resolved into two pairs of items represented by the two lines of the table. The items in the same horizontal line record the part taken in the exchange by one of the two exchangers. This pair of items constitutes his transaction, while the remaining pair constitutes, in like manner, the transaction of the other party to the exchange. The term “ transaction,” though somewhat vague in ordinary use, appears well suited to express the share in an exchange of one of the two who participate in it. Every exchange, then, consists of four items, and may be resolved either into two transfers (one for each prop- erty exchanged) or into two transactions (one for each exchanger). The first resolution has been considered; we proceed now to the second, and enter the subject of “ double-entry bookkeeping.” By double entry is meant the record of every double- faced event pertaining to a particular person, whether it be a transaction of that person with another or an in- teraction between the various categories of capital within his own possession. Double-entry book-keeping is most perfectly illustrated in the case of a fictitious person. The following account represents the entries during a given year for a dry goods company. In this account we observe that every item on the income side is balanced