Table Bay Harbour, Cape Town, is shown to be afflicted by two forms of surging, one of which is responsible for ranging of moored ships, the other for a pumping action of the basins and attendant navigational hazards. The construction and operation of a distorted model of Table Bay and harbour to reproduce the phenomena are descriptionbed. The model was proof tested in various ways and found reliable. Efforts to control the surging were directed chiefly to the Duncan Basin. Internal structures and re-positloning of the basin entrance failed to reduce the disturbances to harmless proportions. Suitable external structures of outer basin type, on the other hand, proved capable of inhibiting effects in the Duncan Basin. Success of the chain-system of basins is ascribed to its throttling effect on the long wave energy In the frequency range critical for moored ships. Measurements and theoretical considerations of ship motions and statistical analysis of rope breakages and damage all confirm that the critical period range for shipping is below 2 min and more particularly in the neighbourhood of 1 min.
The paper descriptionbed an investigation which had been carried out to determine the concrete- and mortar-making properties of crusher sand derived from the crushing of Witwatersrand quartzite at two different crushing plants. It was concluded that such crusher sand, manufactured under controlled conditions, warranted consideration for use in concrete and mortar.
The first section ofthe paper deals with the literature on hardening of bitumens, with particular reference to critical penetration and ductility limits as affecting the disintegration of road surfaces. Contributory causes are discussed. The second part of the paper is devoted to a critical survey of experimental methods for the evaluation of binder durability.