Preparing strewn slides for quantitative microscopical analysis; a test using calibrated microspheres

A known mixture of three sizes of polystyrene microspheres was used to examine the random settling method and the traditional pipetting method of strewn slide preparation. Conventions for counting fragments of microfossils were evaluated also. Results indicate that slides prepared by the pipetting technique yield erroneous data, whereas the random settling technique produces an accurate sample of the original material. Furthermore, counting fragments of particles can bias results toward the larger particles.