SENSE ORGANS OF 
disentangling its effect from the other 
and much larger linear accelerations 
experienced as the result of wind irreg- 
ularities, etc. But the effect on a ro- 
tating body is different. Consider the 
special case of a liquid-filled tube (fig. 
10) rotating with the earth. 
And suppose it also to spin about the 
axis WE so that at the instant illus- 
BIRDS—PUMPHREY 
327 
and current would vary in a ring- 
shaped conductor rotating in a mag- 
netic field. 
If we now suppose the tube to 
represent one of the horizontal semi- 
circular canals of a bird, it is evident 
that if the bird nods its head in the 
N-S direction a circulating current 
will tend to occur in the endolymph 
i 
9 
FicurE 10.—Diagram of liquid-filled tube rotating with the earth. 
trated the north limb is descending. 
At this instant the liquid in the north 
limb has its maximum velocity toward 
the earth’s spin axis and that in the 
south its maximum velocity away 
from it. In the result the Coriolis 
force is a couple acting on the liquid 
causing it to flow around the tube. 
For a constant rate of spin the Coriolis 
couple and hence the flow vary 
sinusoidally, precisely as the e. m. f. 
817369—49—_26 
of these canals while a nod in the E-W 
direction will have no effect. More- 
over the circulation due simply to the 
inertia of the endolymph when the 
head nods is limited to the vertical 
canals. 
The Coriolis force could in this way 
be separated from other forces and 
could therefore in theory be used as 
an indication of true bearings. In 
fact a large-scale working model has 
