308 
PROFESSOE 0. REYNOLDS AND MR. M'. H. MOORBY 
not determined solely by the vortex motion unless the state of pressure at the centre 
of the vortices is fixed, for the vortex motion only determines the difference between 
these pressures. To insure the constant pressure, and at the same time to allow of 
the pockets being only partially full—that is, to allow of hollow vortices with air 
cores at atmospheric pressure, it is necessary that there should be free access of air 
to the centres of the vortices, and as this access cannot be obtained through the 
water, which completely surrounds these centres, it is obtained by passages (|- inch 
diameter) within the metal of the guides, which lead to a common passage opening 
to the air on the top of the case (figs. 2 and 3). 
To supply the break with water there are similar passages in the vanes of the 
wlieel leading from the box cavity, which again receives water through ports which 
Fig. 3. 
open opposite an annular recess in one of the disc faces of the case into which the 
supply of water is led, by means of a flexible indiarubber pipe from the supply 
regulating valve. 
The water on which work has been done leaves the vortex pockets by the clear¬ 
ance between the disc surfaces of the wheel and case, and enters the annular chamber 
between the outer periphery of the wheel and the cylindrical portion of the case, 
which is always full of water \vhen the wheel is running, whence its escape is con¬ 
trolled by a valve in the bottom of the case, from which it passes to waste. 
By means of linkage connected with a fixed support and the brake case, an 
automatic adjustment of the inlet and outlet valves, according to the position of 
