THE MICRO-ORGANISMS PRESENT IN THE ATMOSPHERE. 
143 
No. 3. Hesse’s method. 
Time.— 4.50 p.m. to 5.35 p.m. 
Volume of air =10 litres. 
Colonies in tube 
30 
control-tube 
[16 moulds. 
[ 1 liq. 
2 moulds. 
0 liq. 
Colonies in jlasks. —(a) 3 
IY. North Chemical Laboratory. October 16, 1886. Saturday afternoon; quite 
empty, and only a few (12) students had been working in the morning. 2.3 p.m. 
to 2.35 p.m. 16 0, 9 C. 
Nos. 1 and 2. Flask method. —(Double plugs.) 
No. 3. Hesse’s method. 
Nos. 1 and 2 were alternated in aspiration ; No. 3 was simultaneously 
aspirated in close proximity, the tubes being inclined at the same 
angle. 
No. 1. Volume of air =18 litres. 
Construction of plugs.—(a) Glass-wool only. 
(b) Sugared glass-wool and sugar-powder. 
Rate. —5‘3 strokes per minute. (Tube exposed 14 minutes.) 
22 moulds. 
0 liq. 
( b ) 1 mould. 
No. 2. Volume of air =12 litres. 
Construction of plugs. — (a) Sugared glass-wool. 
(6) Sugared glass-wool and sugar-powder. 
Rate. —5 strokes per minute. (Tube exposed 8 minutes.) 
~ 7 . . 7 . . r 14 moulds. 
Colonies in jlasks. —(a) 26 j ^ ^ 
. {b) °- iq ' 
Control-tube , containing plug of sugared glass-wool, exposed 37 minutes :— 
Colonies in flask, 0. 
. 7 . . . . 777) /. . fNo. 1 (glass-wool), 18 colonies. 
9 litres of air yielded, therefore, m\ , T , A _ 
J J J 5 [No. 2 (sugar-wool), 20 
No. 3. Hesse’s method. 
Volume of air = 9 litres. 
Colonies in tube . . . 13'" 
control-tube 
11 moulds. 
1 licp 
1 mould. 
1 V 
iq. 
* A liquefying colony liad spread considerably, and may therefore have obliterated some of the 
others, and the result is, therefore, probably somewhat too low. 
