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.
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Hamilton et al. (1954) studied this question.
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