THE MICRO-ORGANISMS PRESENT IN THE ATMOSPHERE. 
123 
VII. Laboratory window (same). July 21, 1886. Wind, S. by S.E., fairly strong. 
Dust was being blown about in street below. 2 3°'9 C. 
Volume of air aspirated = 119 litres. 
Construction of plug. —Sugared glass-wool and sugar-powder. 
Rate .—About 3’5 strokes per minute. 
Plug mixed with 20 c.c. of sterilised water, 1 c.c. of which gave on plate- 
cultivation :— 
Colonies, 77, 63, 65. . . Average = 68’3 colonies. 
Control-plates with sterilised water gave 
colonies 12, 4 . . . . Average =8 „ 
119 litres of air yielded .'. 60'3 X 20 = 1206 ,, 
10 „ „ 101 
VIII. Laboratory window (same). July 22, 1886. Wind, S.W., strong, variable in 
strength and direction. 23 0, 9 C. 
No. 1. Volume of air aspirated = 119 litres. 
Construction of plug .—Sugared glass-wool and sugar-powder. 
Rate .—About 5'1 strokes per minute. 
Plug mixed with 20 c.c. of sterilised water, 1 c.c. of which gave on plate- 
cultivation :— 
Colonies, 97, 55, 61 . . . Average = 71 colonies. 
Control-plate with sterilised water gave 3 ,, 
119 litres of air yielded .’. 68 X 20 = 1360 „ 
10 „ „ 114 „ 
No. 2. Wind stronger than in No. 1, and much dust blowing about. 
Volume of air aspirated = 119 litres. 
Construction of plug. —Glass-wool and glass-powder. 
Rate .—47 strokes per minute. 
Plug mixed with 20 c.c. of sterilised water, 1 c.c. of which gave on plate- 
cultivation :— 
Colonies, 107, 103, 110 . Average = 1067 colonies. 
Control-plate with sterilised water gave 6 ,, 
119 litres of air yielded /. 1007 X 20 = 2014 „ 
10 „ „ 169 
IX. Laboratory window (same). July 26, 1886. Wind, W. by S.W. Copious rain 
during previous day and night, but roads and pavement dry at time of experi¬ 
ment. 20° C. 
No. 1. Volume of air aspirated = 119 litres. 
Construction of plug .—Sugared glass-wool and sugar-powder. 
Rate. —3‘8 strokes per minute. 
