42 ROYAL SOCIETY OF CANADA 
a series of experiments at Tokyo throughout a whole year, and we 
refer the reader to his paper for the literature of the subject. 
METHODS. 
Two methods have been employed: (1) the volumetric, and (2) the 
plate method; and parallel determinations have been made weekly, 
without any break, during the whole of one year. This is the first 
time that parallel observations by these two methods have been car- 
ried on during so long a period of time. The curves given by the 
results are not identical in form, and a study of them shows that vari- 
ations in external conditions do not result in parallel variations in 
the number of micro-organisms given by the two methods. Thus, for 
instance, a strong wind increases the number of micro-organisms 
settling upon an exposed plate to a much greater relative extent than 
it increases the number in 10 litres of air. 
The Volumetric Method.—The volumetric method is practically 
that devised by Professor Percy Frankland! for his experiments in 
England. However, for the experiments carried out on the campus 
of the university of Manitoba, it was found convenient to substitute 
a ten-litre aspirator for a pump, in order to draw the air through the 
collecting tubes. To this extent Frankland’s method has been sim- 
plified and rendered much easier in carrying out, more especially 
during the great cold of the winter months and during those weeks 
in summer when mosquitoes are troublesome. 
The essential parts of the apparatus were as follows: (1) two 
collecting tubes, which we shall term the experimental and control 
tubes respectively; (2) an aspirator capable of aspirating 10 litres of 
air through the experimental tube; and (3) a piece of lead piping ten 
feet long, by means of which the experimental tube was connected 
with the aspirator. 
‘When the aspirator was set up on the University campus, it had 
the appearance shown in Fig. 1. The experimental and control tubes 
were attached to a clamp-stand at a height of about two feet from 
the ground, and the aspirator was supported on a stool. 
The experimental tube (Fig. 2, A) was constructed from a glass 
tube which was 5 inches long and had an internal diameter of 0.25 
inches. It was heated in a flame so as to make a constriction (Fig. 2, c), 
about 1.25 inches from one end. Some glass wool was pushed down 
the tube with the help of a small glass rod, so as to form a layer on one 


‘PP. F. Frankland. A new method for the quantitative estimation of the micro- 
organisms present in the atmosphere. Phil. Trans. Roy. Soc., Vol. 178 (1887) 
B, pp. 113-152. 
