This test method has been developed to assess the deterioration of rocks over a period of time when subjected to water immersion. The apparatus consists of a motorized drive unit which is mounted on a baseplate and which can rotate two or four drums at a speed of 20 r.p.m. The tank assemblies are filled with water to a level 20 mm below the drum axis. The test drums are manufactured from 2.00 mm mesh, 140 mm dia. x 100 mm long