The sedimentation of clay materials has been considered, and the following results are obtained:
(1) Velocity of sedimentation is influenced by the plasticity of clay materials,
(2) Reynolds Number Relation is unable to be applied to the sedimentations of Chikuho clay and Zettlitz kaolin, but the sedimentation of Yakusa Kibushi clay and Sidare Kibushi clay can be analysed successfully by Re-Relation.