282 
MR. S. DUNKERLEY ON THE WHIRLING 
speeds were afforded by one of Professor PtEYNOLDs’ quadruple turbines working 
under a constant head of 113 feet of water. 
The essential parts of the apparatus by which the different formulae were verified 
consisted of a (see fig. 1) cast-iron bed i^late, of stiffened channel section, 3 feet 
6 inches long and 4 inches wide, with its top and bottom faces planed parallel ; 
a headstock which was 7^ inches high, 4 inches wide, and 4 inches long, with its 
bottom face planed ; a headstock spindle (which receives the motion), ^ inch diameter, 
and provided with a shoulder at one end, a loose collar, and two speed pulleys, one 
Fi-. 1. 
for directly receiving the motion, the other for transmitting the motion to a centri¬ 
fugal fan indicator, which approximately indicates the speed of the headstock 
spindle, at any instant, by the height of a column of liquid forced by the fan up 
a glass tube. The scale of the indicator was graduated by accurately determining 
the speeds required to force the liquid up to two or three definite heights, and 
so obtaining a formula by means of which the heights due to certain speeds can be 
calculated. The formula so obtained was 
where 
N = number of revolutions of headstock spindle per minute, 
