Factors in the design of a microscope eyepiece graticule for routine dust counts

Abstract

The limitations of existing microscope eyepiece graticules for use in routine dust counting work and the problems of determining the geometrical form and physical dimensions of a graticule for use with commercial microscope equipment are discussed. Comparison is made of the consistency and accuracy obtainable with three types of graticule: the Patterson-Cawood, a simplified globe and circle type and a parallel line graticule. The simple globe and circle graticule described has been taken into general use in the National Coal Board.