The author calculated, using Pasquill's chart, the logical concentration of sulfur dioxide concerning principal 15 chimneys in many places of Mizushima industrial area which had emitted 74 percent sulfur dioxide over Mizushima, and compared concentrations measured practically at the respective station of Fukuda-cho, Mizushima Harbor Office and Amagi with the logical concentration calculated by Pasquill's chart. The results obtained were as follows. 1. The high concentrations of sulfur dioxide measured practically at Fukuda-cho station could be logically explained by the diffusion called C-stability following Pasquill, and those at Amagi station could be also explained by the diffusion called D-stability. 2. Under the condition of each of A and B stabilities following Pasquill, sulfur dioxide diffused itself significantly on C-stability in Pasquill's chart, and in the case of each B and C stabilities, it diffused itself on D-stability in Pasquill's chart.