196 FUMIGATION METHODS 
center of the room, one near the ceiling, one near the 
floor, and one midway between, after twenty minutes 
practically the same amount of vapor on an average is 
found at the ceiling and at the middle point, whereas 
the space near the floor shows about one-third as much 
as the other two. 
‘‘Where the generator is covered with a box 
that extends on all sides to the floor, the effect is 
to throw the vapor down to the floor. The results 
show a greater amount there than in the preceding 
arrangement. This device is quite inadequate to 
secure an even distribution of vapor. 
‘‘In this test the generator was placed two feet 
from a side wall at the middle point, and provided with 
a horizontal distributing tube. The intakes were in a 
vertical line in the center of the room. ‘The effect of 
this simple arrangement was surprising. After ten 
minutes there was practically a uniform distribution of 
acid vapor, at least in so far as the three points of 
sampling may be taken as typical, and they seem to be 
fairly representative. After twenty minutes there was 
found to be but a slight change, well within the limits 
of flu@tuation in work of this sort. This simple device, 
designed by Professor Sanderson, is shown in Chapter 
XII. The acid vapor is distributed immediately with 
surprising uniformity. Thus has been solved perfectly 
the difficulty of securing an even and speedy diffusion, 
and that, too, in a very simple and practicable way. 
‘These results may be taken as showing fairly well 
how much of the hydrocyanic acid can be accounted 
for, and that is 93 per cent. of what is actually evolved, 
or about 88 per cent. of the total amount contained in 
