THE MICRO-ORGANISMS PRESENT IN THE ATMOSPHERE. 
135 
Experiments with Doubly Plugged Tubes. 
Of 
5 ’ 
I. Roof of Science Schools. September 23, 1886. Wind N. by N.W., fairly stron 
variable in direction. No recent rain. Nos. 1 and 2 were alternated in aspiration. 
2.48 p.m. to 4.56 p.m. 
No. 1. Volume of air =30 litres. 
Construction of plugs. — (a) Sugared glass-wool only. 
(h) Sugared glass-wool and sugar-powder. 
Rate. —2 ‘5 strokes per minute. (Tube exposed 47 minutes.) 
„ , . . _ , , . ^ r 58 moulds. 
Colonies in flask. — (a) 94 j ^ ^ 
(h) 0. 
No. 2. Volume of air =27 litres. 
Construction of plugs. — (a) Sugared glass-wool only. 
(6) Sugared glass-wool and sugar-powder. 
Rate. —1’4 stroke per minute. (Tube exposed 66 minutes.) 
~ , . . n . . . ^ f 36 moulds. 
Colonies m flash. —(a) 100 j ^ y 
. {b) °‘ 
Control-tube, containing plug of sugared glass-wool only, was exposed during 
81 minutes :— 
0 mould. 
Colonies in flask, 12 
1 liq. 
This corresponds to 1 organism falling on the plug in 7 minutes; from 
the result of No. 1, 47 -P 7 = 7 must be subtracted, and, from No. 2, 
66 ■— 7 = 9 colonies, since tube No. 1 was exposed 47 and No. 2 
66 minutes. 
'No. 1, 29 colonies. 
10 litres of air yielded, therefore, in 
No. 2, 34 
II. Roof of Science Schools. September 28, 1886. Wind S.W. by W., variable in 
direction, gentle. Dust blowing about in street below. 17°-16° C. Nos. 1 and 2 
alternated in aspiration. 3.40 p.m. to 4.58 P.M. 
No. 1. Volume of air = 24 litres. 
Construction of plugs. —(a) Sugared glass-wool only. 
(b) Sugared glass-wool and sugar powder. 
Rate. —2 - 8 strokes per minute. (Tube exposed 29 minutes.) 
„ 7 . . _ 7 , s f 47 moulds. 
Lolomes m flash. —(a) 63 j ^ ^ 
(b) Lost. 
