The routes to monopoly are very numerous and it would be tedious to attempt to provide anything approaching a complete list of them. We cannot proceed further with our study, however, until the most commonly used have been described. We have already referred to the broad distinction between terminable associations and close combines (or monopolies of scale), that is to say, between monopolies that rest upon restrictive agreements for a term of years among independent firms, and those which depend upon the dominance of single firms and in which the separate identities of former members of the industry have been wholly or largely destroyed by financial combination. At the extremes this distinc tion is sharp, but there is a wide area where it becomes blurred and imprecise. This, indeed, is true of almost every kind of industrial classification.