The term "nett deckle width" applies to the width of the trimmed finished paper at the end of the machine. The formula takes no account of the allowance required for trimming edges. In most cases the deckle width of the machine is arranged so that the paper is cut into strips of equal width when leaving the calenders, _e.g._, a deckle of 80 inches will give 4 sheets, each 20 inches wide. [Illustration: FIG. 39.--Paper Machine showing Wire, Press Rolls, and Drying Cylinders.] The method by which the general formula is obtained may be explained by an example. What is the output of a machine having a speed of 100 feet per minute, with an 80-inch deckle, producing a sheet of paper 20 inches by 30 inches, weighing 30 lbs. per ream of 480 sheets? The machine produces every minute a sheet of paper 100 feet long and 80 inches wide. Hence output per minute in square inches = 12 × 100 × 80. Output per hour in square inches = 60 × 12 × 100 × 80. Now each (20 × 30 × 480) square inches is area of one ream. Output of paper per hour in reams 60 × 12 × 100 × 80 = ------------------. 480 × 30 × 20 Output of paper per hour in lbs. 720 × 100 × 80 × 30 = ------------------- 480 × 30 × 20 = 600 lbs. The general formula may be applied for the purpose of calculating the speed at which the machine must be driven. _Example._--A machine with 75-inch deckle is required to produce 6 cwts. per hour of a paper 25 inches by 18 inches (500 sheets), weighing 19 lbs. to the ream. At what speed is the machine to be driven? Output in lbs. per hour 720 × _F_ × _D_ × _R_ = --------------------- _S_ × _L_ × _W_ 720 × F × 75 × 19 672 = ----------------- 500 × 18 × 25 _F_ = 148 feet per minute. CHAPTER VI BROWN PAPERS AND BOARDS