COMPOSITE SLIDE RULE

A composite slide rule showing for different type breadths defining the number of characters in a printed line the number of characters printed for various numbers of lines printed with such types. Advantageously, there is provided an elongated casing with a plurality of parallel channels the cross-section of which is preferably in the shape of a regular polygon such as an equilateral triangle, these channels slidingly housing prismatic slides of a corresponding cross-section, the sides of which carry each along its opposite edges cooperating scales of character and line numbers for a predetermined type breadth. This allows reading, through gates extending through the casing, the corresponding character and line figures for the selected character breadth.