224 



Cincinnati Society of Natural History. 



At least 6 species were present, viz: A,, A 2 , A3, A,, A 6l 

 and A 10 . 



Exp. ig — October 20, 1899, 5.25 p. m. Plates were ex- 

 posed as in previous experiment but in business portion of 

 town, i. e. on sidewalk on Gold Avenue. Time — 10, 15 

 and 30 minutes. No wind. 



October 25: 



PI. 10 min. — 1,197 bacteria, 13 molds and 1 yeast. 

 PI. 15 min. — 1,827 bacteria, 15 molds and 5 yeasts. 

 PI. 30 min. — 2,036 bacteria, 17 molds and 3 yeasts. 

 Average per 10 min., 1,031 bacteria. 



Exp. 20 — Jan. 25, 1900, 5.00 p. m. Three agar plate ex- 

 posures were made in same place as for previous experiment, 

 but for shorter time — 1, 3 and 5 minutes. Former plates 

 were too heavily seeded. 



February 12: 



PL 1 min. — 725 bacteria or 7250 per 10 min. 

 PI. 3 min. — 976 bacteria or 3253 per 10 min. 

 PI. 5 min. — 1,228 bacteria or 2456 per 10 min. 

 Average, 4,320 per 10 min. 



Exp. 21 — January 26, 1900, 3.00 p. m. Three agar plates 

 were exposed under same conditions as in Exp. 18, i. e. in 

 front yard of private residence. Time — 20, 40 and 60 minutes. 



February 12: 



PI. 20 min. — 980 bacteria or 455 per 10 min. 

 PI. 40 min. — 1,373 bacteria or 343 per 10 min. 

 PI. 60 min. — Spoiled. 

 Average, 394 per 10 min. 



Exp. 22 — March 17 and 18. Four agar plates were exposed 

 on Gold Avenue as in Kxps. 19 and 20, but the first pair of 

 plates were exposed in the evening at the close of business; 

 the second pair the following morning. 



6.00 p. m., Mar. 17 (Saturday) — PI. a — 2 min. PI. b — 4 min. 



8.30 A. m., Mar. 18 (Sunday) — PI. £—2 min. PI. d — 4mm. 



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