By analyzing nineteenth-century mental health data, college level geography students discover the concept of distance decay, which describes the decrease in intensity of a phenomenon with increasing distance from some central place. (RM)

Population models, both flat and vertical, make excellent group activities. Methods of instruction are detailed with examples. Models may be used to make transformations to demographic base maps upon which other population characteristics may be shown. (NH)

A given discipline and the relationships contained within it are frequently portrayable in diagrammatic or schematic form. The model offered in this article may serve to convey ideas on organization and purpose in geography by showing basic elements and relationships. (Author)

Presents the results of a field study done on 7 wells providing 37% of the total aquifer production for 4 municipalities in Puerto Rico. Each sampled well showed signs of contamination by heavy metals, nitrate, and semivolatile organic compounds. Although found in low concentrations, current development threatens groundwater quality. (MJP)