If you want to measure the proportions of different kinds of material, weigh the jar before you start the investigation. Now get your river bed sample including the water. Weigh the jar and contents. Swill the water in the jar, wait two minutes and then pour off the muddy water into another jar. Weigh what is left in the first jar. Take the weight of the empty jar from this new weight and you have the weight of stones, sand and gravel. Put the stones, gravel and sand to one side and put the muddy water back in the jar. Stand the jar somewhere warm until the water has evaporated and the mud dried out (a few days). Weigh the jar and dried mud and take away the weight of the empty jar. This is the weight of silt and clay.
