220 



Cincinnati Society of Natural History. 



October 27 : 



PI. 24 min. — 161 bacteria and 8 molds. 

 PL 40 min. — 242 bacteria and 19 molds. 

 PI. 60 min. — 187 bacteria and 24 molds. 

 Average per 10 min., 52.8 bacteria. 

 Spp. present: A,, A 2 , A 3 , A 4 , and A 12 . 



The following three experiments may be included here, 

 though they really constitute a single experiment. Their 

 object is to show the effect of rain in clearing the atmos- 

 phere. The first experiment (No. 15) as the data show, was 

 made soon after a considerable rain. The other experiments 

 follow on successive days. 



Exp. 75 — November 15, 1899, 3.53 p. m. Three agar plates 

 were exposed east of Gymnasium after a heavy rain ( T % in.) 

 which fell at noon to-day. There were slight previous showers 

 also. The ground was thoroughly wet down. Atmosphere, 

 clear. Slight breeze from southeast. 



November 28: 



PI. 20 min. — 7 bacteria and 10 molds. 



PI. 40 min. — 10 bacteria and 18 molds. 



PI. 60 min. — 10 bacteria and 27 molds. 



Average per 10 min., 2.5 bacteria. 

 Three species: A,, A 2 , As, 



Exp. 16 — November 16, 1899, 3.23 p. m. Exposed three 

 agar plates for same time and in same place as in previous 

 experiment. Soil still quite damp. Atmosphere, clear. 

 Quite strong wind from southeast. 



November 28: 



PI. 20 min. — 51 bacteria and 4 molds. 

 PI. 40 min. — Spoiled. 

 PI. 60 min. — 23 bacteria and 9 molds. 

 Average per 10 min., 14.65 bacteria. 



Exp. 77 — November 17, 1899, 3.04 p. m. Agar plates were 

 exposed as before, under following conditions: Very slight 

 dust beginning to appear. Cloudy, with practically no wind. 



10 



