In 1951 the celebrated British hydrologist H.E. Hurst published a paper titled, “The Long-Term Storage Capacity of Reservoirs.” The paper dealt specifically with the modeling of reservoirs, but as it turned out, the results also held valid for a number of other natural systems. Hurst was looking for a way to model the levels of the river Nile so that architects could construct an appropriately sized reservoir system. While his recommendations were not implemented (the 1952 Egyptian revolutions saw to that), he gave life to a statistical methodology for distinguishing random from non-random systems and to identify the persistence of trends, a methodology known as Rescaled Range analysis or R/S analysis.