development. The late William E Petersen characterized the barometric varia bility over the North American continent as the "footprint of As clepius." To him the concentration of the great storm tracks along the northern border of the United States was a portrayal of the areas of maximal meteorological demand on the organism. The chart of a single year served him as corollary evidence: "Mean barometric var iability for 50 stations for the year 1930."1 Other authors have stressed meteorological variability, ex pressed in temperature changes, as an important health and pro ductivity factor. Huntington expressed it as follows: "Uniformity of temperature causes low energy." "Days when there is no change of temperature are not particu larly favorable . . . ." "It seems most significant that the Connecticut men . . . are most stimulated by a strong change of temperature."