1915-16.] The Dynamics of Cyclones and Anticyclones. 185 
from a vessel such as is shown in fig. 3, in which a circular motion is given 
to the water, and precautions are taken to prevent air entering either from 
above or from below, though the outlet he full of water the outflow is 
greatly retarded. It is found that the amount of retardation depends on 
the diameter of the outlet. In a vessel of the dimensions given above, if 
the outlet be 2 cm. the retardation amounts to 50 per cent., more or less 
according to the rate of rotation ; but if the opening be only 1 cm. the 
retardation is much less, and it is very small in the cyclone of the propor- 
tions shown in fig. 1, where the outlet is only 0'5 cm. 
{Issued separately September 30 , 1916 .) 
