The principle underlylng the measurement of moisture content and density of soil layers by radio-isotopes is already well known. Based on this principle, an Instrument, called the Hidrodensimeter, has been developed by the National Institute for Road Research and is briefly descriptionbed. The results of comparattve field tests with this instrument and the sand-replacement method are discussed, and it is concluded that the new instrument will measure moIsture content and density with a reliability at least equal to that of the sand-replacement method.
The paper descriptionbed the construction and operation of a 'distorted' model of Table Bay and harbour to reproduce two forms of surging which occur in the actual harbour, one of which is responsible for 'ranging' of moored ships and the other for a 'pumping' action of the basins. Various schemes to overcome these difficulties which were tried in the model, were also descriptionbed.
This paper summarises all the data available to the Irrigation Department concerning the silt load of South African Rivers. It also presents a method of determining the probable useful life of a dam built across a silty river.