From The Indianapolis Star, Friday, November 21, 1919: Nineteen tons of soot is falling annually for each city block in the downtown Indianapolis area. This conclusion was arrived from calculations made by students in the night school physics class at Manual Training High School who conducted tests under the direction of their teacher Louis Karns. Using equipment similar to rain gauges that were placed on the rooftops of downtown buildings, the average sootfall collected at all points was .00119 milligrams for each square inch of surface. Cinders and small grains of coal were excluded from the study, so the sooty precipitation included nothing but the carbon present in flue gases, which falls with atmospheric condensation during the night. A similar study was done in St. Louis that showed an annual fall of fifty tons of soot for each city block.