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This paper investigates the significance of structural theory solutions for structures composed of perfectly plastic materials when the loading is of a highly localized nature. Limit analysis is applied to illustrative problems in order to compare the actual collapse loads with those provided by the structural theory. For strip loading problems it is found that, as the width of the loaded region decreases, the transition from failure predicted by structural theory to failure due to local plastic flow is very abrupt, and the structural theory is accurate even for strip widths which are small compared to the thickness of the structural element. For a circular plate under a central disk of pressure, however, the results obtained indicate that plate theory does not apply when the diameter of the disk is less than the plate thickness.

At the VIII. International Sedimentological Congress held in Heidelberg in 1971, a symposium with the above title was convened; a selection of the papers presented is assembled in this issue. In the introduction the approaches of the following studies are reviewed to show some trends and problems in reef research.

The papers in this issue comprise those given at the first day's session of the Fourth Chemical Finishing Conference of the National Cotton Council of America, held at Atlantic City, N. J., September 20-21, 1955. The remaining papers will appear in the February issue. A reprint of the entire proceedings, bound in a cover, will be dis tributed through the National Cotton Council.

The driver tries to keep the car in the center of the lane. If the car is too near the left edge, this causes the driver to make a “corrective” right turn. If the car is near the right edge, a “corrective” left turn is made. Therefore, a quantity which decreases with increasing distance ΔL from the left edge may be considered as a stimulusSR producing the reactionRR of turning to the right. A similar situation holds for the distance ΔR from the right edge. When the car is in the center of the lane, ΔL = ΔR andSR=SL, the stimuli are equal. We thus have here a situation analogous to the one studied by H. D. Landahl in his theory of psychophysical discrimination. In general a reactionRR (resp.RL) will occur only ifRR−RL≥h* (resp.RL−RR≥h*) whereh* is a threshold. Applying Landahl’s theory to this situation, we find thath* determines the distance from the edge, at which a corrective turn is made. This distance is not constant, but a function of the speedv of the car. The requirement that a corrective turn should be madebeforre the car runs off the road leads to an expression for the maximum safe speed. Because of the transcendency of the equations involved, closed solutions cannot be obtained. It is, however, shown that the expression for maximum safe speed, given in a previous paper (Bull. Math. Biophysics,21, 299–308, 1959), is a rough first approximation to the expressions found now.