flowing fresh water springs discharged along the western shore of Biscayne Bay at elevations of from 3 to 5 feet-above mean sea level, thus indicating a high water table close to the shore line. These springs have long since ceased to flow, and the lowered water table no longer exerts sufficient pressure on the heavier salt water from the ocean to hold it back, so the salt water has moved inland as a blunt-nosed wedge underneath the lighter fresh water. This salt water wedge, in the Silver Bluff area, has advanced inland about 8,000 feet. Plate 5 shows maps of the Miami area indicating the zone of' salt water contamination in 1904p. 1918, and 194i3. The maps for 19041 and 1918 are largely based on estimated and known conditions, but that for 194f3 is principally based on samples from we ,lls generally more than 60 feet deep. These maps clearly show the trend of salt water advancing inland and displacing fresh water. They show that salt water has not yet reached the Miami well field by direct infiltration from the Bay at depth in the aquifer, and likewise show why it was necessary in 19411 to abandon the ground water supply at the Coconut Grove water plant. Elsewhere along the coast the distance that the salt water has penetrated inland may be more or may be less than 8,000 feet depending upon the effectiveness of the nearby drainage canals in lowering the water table. This blunt-nosed salt water wedge encroaches haltingly, with many minor advances and retreats, and it probably will continue in this manner until eventually it will come to rest in equilibrium with fresh water where the average annual two and one-half foot contour on the water table occurs# During the short period of this investigation (4~ years) the critical two and one-half foot water table contout' has generally paralleled and lain slightly to the west of Red Road, and has passed to the west of the-present well field. (see plate 6).