The need for this differentiation accelerated the tendency to reduce the size of types, which was doubtless in the first place dictated by a desire for economy. The earlier German text-types for ordinary books very commonly measure about 6 mm. a line. To enable small differences to be shown they are quoted in the British Museum Catalogue of Incunabula by the measurements of twenty lines, and many of the early Mainz and Strassburg types range closely round the number 120. These large text-types are often the only ones used in a book, notes or other accompaniments of the text being clumsily indicated by brackets or spaces. The better printers, however, gradually imitated Fust and Schoeffer, and along with their 120 text-types used smaller commentary types measuring about 4 to 4(1/2) mm. a line, or from 80 to 90 mm. for twenty lines. In the great folio commentaries on the Canon and Civil Law a very fine effect is produced by two short columns of text in large type being placed two-thirds way up the page and then completely surrounded by the commentary in smaller type, also in double columns. But the economy of using the smaller type for the text of books without commentary was quickly perceived, and along with 4 to 4(1/2) mm. small text-types, heavy and often rather fantastic types of just twice this size (8 to 9 mm. a line, 160 to 180 mm. to twenty lines) came into use for headings, and the opening words of books and chapters. The same course was followed with respect to headlines, when it was desired to add these to a book without the aid of a scribe. Eggestein printed one book with headlines in red, but the same heavy type which was used for chapter headings was soon used for headlines, and also, with very ugly effect, for numbering the leaves.