ON THE VORTEX WATER-WHEEL. 319 
the brass. A cavity, shown in the Plates, is provided at the lower part of 
the cup, for the purpose of preventing the oil from being rapidly washed 
away by the water*. 
Four tie-bolts, marked P, bind the top and bottom of the case together, so 
as to prevent the pressure of the water from causing the top to spring up, 
and so occasioning leakage at the guide-blades or joint-rings. 
The height of the fall for this vortex is about 37 feet, and the standard or 
medium quantity of water, for which the dimensions of the various parts of 
the wheel and case are calculated, is 540 cubic feet per minute. With this 
fall and water supply the estimated power is 28 horse power, the efficiency 
being taken at 75 per cent. The proper speed of the wheel, calculated in 
accordance with its diameter and the velocity of the water entering its cham- 
ber, is 355 revolutions per minute. The diameter of the wheel is 223 inches, 
and the extreme diameter of the case is 4 feet 8 inches. 
A low-pressure vortex, constructed for another mill near Belfast, is repre- 
sented in vertical section and plan in Plates 3 and 4. This is essentially the 
same in principle as the vortex already described, but it differs in the material 
of which the case is constructed, and in the manner in which the water is led 
to the guide-blade chamber. In this the case is almost entirely of wood ; and, 
for simplicity, the drawings represent it as if made of wood alone, though in 
reality, to suit the other arrangements of the mill, brick-work, in certain 
parts, was substituted for the wood. The water flows with a free upper sur- 
face, W, W, into this wooden case, which consists chiefly of two wooden 
tanks, AA and BB, one within the other. The water-wheel chamber and 
the guide-blade chamber are situated in the open space between the bottom 
of the outer and that of the inner tank, and will be readily distinguished by 
reference to the figures. The water of the head race, having been led all 
round the outer tank in the space CC, flows inwards over its edge, and passes 
downwards by the space DD, between the sides of the two tanks. It then 
passes through the guide-blade chamber and the water-wheel, just in the 
same way as was explained in respect to the high-pressure vortex already 
described; and in this one likewise it makes its exit by two central orifices, 
the one discharging upwards and the other downwards. The part of the 
water which passes downwards flows away at once to the tail race, and that 
which passes upwards into the space E within the innermost tank, finds a 
free escape to the tail race through boxes and other channels, F and G, 
_ provided for that purpose. The wheel is completely submerged under the 
surface of the water in the tail race, which is represented at its ordinary level 
at YYY, Plate 3, although in floods it may rise to a much greater height. 
The power of the wheel is regulated in a similar way to that already de- 
scribed in reference to the high-pressure vortex. In this case, however, as 
_will be seen by the figures, the guide-blades are not linked together, but each 
is provided with a hand-wheel, H, by which motion is communicated to 
itself alone. 
* Great stress has been by continental engineers and authors laid on the supposed neces- 
sity for oiling the pivots of turbines. The author of the present communication has thus been 
led to endeavour to find and adopt the best means for oiling pivots working under water. The 
oiling, however, is a source of much trouble; and he has found in the course of his experience, 
that pivots of the kind described above, made with brass working on hard steel, and with a 
radial groove in the brass suitable for spreading water over the rubbing surfaces, will last well 
without any oil being supplied. The rapid destruction, which is commonly reported as having 
been of frequent occurrence in turbine pivots, he believes may in many cases have arisen from 
the employment of an inverted cup like a diving-bell as one of the rubbing parts, without any 
provision for the escape of air from the cup. It is evident that a pivot of this kind, although 
under water, might be perfectly dry at the rubbing surfaces. 
