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Elementary analyses of the mean patterns of free convection from a line source and a point source are presented without regard to the specific means by which the gravitational action is produced. The derived functional relationships are then verified and completed through use of velocity and temperature measurements above sources of heat, the generalized form of the results permitting characteristics of the mean flow to be determined over a considerable range of the primary variables. These results should enable meteorologists to evaluate the role of the basic convective process in the more complex movements of the atmosphere.

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Measurements of the velocity, pressure, and turbulence behind a series of normal plates in the uniform test section of an air tunnel are described, the oscillation of the wake being prevented in all but one test through use of symmetrically located tail plates. By a combination of experimental and computational techniques, details of the pattern of flow over a wall on a plane boundary in an infinite fluid are closely approximated. A significant difference is indicated between the characteristics of such a flow and those of the flow past an isolated plate with oscillating wake.

principle of continuity (the conservation of fluid mass) and a form of the work-energy principle known as the Bernoulli theorem. In passing, note was taken of means of measuring velocity, pressure, and discharge, including the use of small-scale models to simulate flow conditions in themselves too large to test. These principles were then applied to the study of flow from orifices, over weirs, through closed and open conduits, and past immersed bodies. Simple as such matters now seem when taught, they actually took centuries to understand. Particularly noteworthy is the fact that many such principles were first clarified by men like Isaac Newton whose in terests extended far beyond hydraulics itself. This science actually had its origins some two millenia ago in the course of Greek civilization. It must be granted, however, that Greek physics was of such a hypothetical nature that-with one exceptionit had little positive influence in the millenia to follow. The part that concerns us here is the then-prevailing belief that the universe consists of four elements (fire, air, water, and earth), that each is displaced by the next in order of increasing weight, and that the space around us must be occupied by one element or another. "Na ture," in other words, "abhors a vacuum." In due time the concept of a fifth element, ether, came into being, for want of something to fill outer space. To the Greeks, the abhorrence of a vacuum served to explain free flight, a body in motion presumedly being driven by the fluid closing in behind. Known as the medium theory of motion,2 this was one of the teachings of Aristotle (384-322 B.C.), who wrote on a wide variety of subjects ranging from physics to metaphysics. The so-called impetus theory of motion was proposed nearly a thousand years after Aristotle's time;3 however, because impetus could not be seen, the concept was not generally accepted, and the medium theory remained in favor for at least another millenium. The Greek who made the most lasting contribution to hydraulics was the Sicilian mathematician Archimedes (287-212 B.C.), who reasoned that a floating or immersed body must be acted upon by an upward force equal to the weight of the liquid that it displaces.4 This is the basis of hydrostatics and also of the apocryphal story that Archimedes made this discovery in his bath and forthwith ran un clothed through the streets crying "Eureka!" Nevertheless, even