Weems & Plath Parallel Plotter. #120. Consists of a roller mounted on a plotter with distance scales of 1:20,000,1:40,000 and 1:80,000 to fit N. O. S. Coast and Harbor charts. Have an inch scale, semicircular protractor and two quarter-circle protractors. Courses and parallel lines are transferred and kept parallel by means of two rollers mounted on a single axis.