The amount of atmospheric ozone was observed at Tokyo during the period from June 1953 to September 1955, using a cadmium photoelectric tube and a glass filter. The observations were made at about 11 a.m. on the day when there was no cloud in the direction of the sun. During this period, 217 independent observations were obtained and their absolute values were determined by a series of comparative observation with Dobson spectrophotometer (No. 52) for the period April through September 1955. With this comparative observation, it was ascertained that by the present method the amount of ozone can be measured with good accuracy.
The amount of ozone shows a marked seasonal variation in respective years having the maximum value in spring and the minimum in autumn. The course of annual ozone variation and its absolute value agree well with the result obtained at Washington D.C. in 1948-1950 by S. Fritz.