The first conclusion that can be drawn from these results is the extreme variation in the size distribution of the particles of the material. Table nine shows the maximum, average and minimum percents of each size found in the roof shales, and table ten shows the same factors for the floor clays. From the reported answers to question A we can also see the wide range of opinion concerning roof shales. Of those materials classed as slate, the sand size varied from 1 to 64 percent, while the material reported as draw-slate fell between these limits with a range of sand size from 3 to 38 percent. / Master of Science