A notation, says H. E. Bliss, is ‘a system of marks or symbols in some order, denoting terms or members of a series or system of things’. For the purposes of classification, he continues, a notation ‘is requisite to maintain the systematic order in schedules and on shelves, and to locate them in this order’. The notation is thus correlative, complementary, and subsidiary to the classified order itself. The classified order reflects, well or ill, the real order of tilings; notation preserves and mechanizes this classified order. ‘The classification is the main thing, and the notation, however real its service, does not make the classification, though it may mar it’.