The circle areas of the Porton greaticules increases with Root 2 progression as do the divisions on the right hand side of the rectangle. These divisions are numbered for convenience. The rectangle size is 4.5 mm x .25 mm. Circle sizes in microns are 560, 400, 280, 200, 140, 100, 70, 50, and 35. The specimen is racked on the mechanical stage of the microscope and traverses are taken right across thee deposit sizing all the particles encountered.
Size: 19mm
Surface: Chrome image