274 The N.Z. Journal of Science and Technology. [Sept. 
driven three-throw pumps, the motor being coupled to the pumps by means 
of belts (or ropes) and gearing. About the same time another school, 
mostly of Continental engineers, introduced the idea of placing the motor 
direct on the crank-shaft of the pump and adopting comparatively slow- 
speed motors. In order to keep the size of the motors within reasonable 
limits the speed of the pumps was considerably increased. The water- 
speed in the pumps was not increased to any great extent, for there is a 
limit to this, but the number of revolutions per minute was greater. This 
necessitated the pump-valves being actuated mechanically, and proved to 
be a very complicated problem. Numerous difficulties and failures were 
encountered, and although to a great extent these difficulties have been 
overcome, yet this class of pump has not realized the anticipation!- of the 
engineers who introduced it. 
The inventive capacity of engineers was therefore directed more and 
more to the three-throw plunger-pump, but the great difficulty was the 
successful application of the electric motor to driving these pumps. It 
was soon realized that whilst belts and ropes formed a flexible medium, 
yet they were an undesirable feature for underground work ; on the other 
hand, gearing, was objectionable, not only on account of its inefficiency, 
but also because of the noise and the vibration. 
The solution was the introduction of double helical machine-cut gearing 
running in oil, and the installation of a flexible coupling between the motor 
and the pumps. This gearing has a high efficiency, is comparatively noise¬ 
less, and the flexible coupling relieves the motor to a great extent of shocks 
from the pump ; and this combination may be considered to b& the most 
efficient and economical so far as these mine-pumps are concerned. 
We now come to the type of pump which in recent years has made 
remarkable progress, and bids fair in the majority of cases to supersede all 
other types, and that is the turbine pump. Now, this pump has not such 
a good efficiency as a high-class three-throw pump, and its efficiency 
decreases rapidly with a diminishing load, but it possesses so many other 
advantages that it is destined to become the most popular pump so far as 
electrical driving is concerned. It is capable of being run at a very high 
speed, and consequently can be coupled direct to a motor ; it is usual when 
running a 50-cycle circuit to fix this speed at 1,500 revolutions per minute. 
The mechanical parts are simple, are easily repaired or renewed, and the 
great advantage is the small space taken up for the amount of work done 
and the consequent saving effected in the excavation of underground 
chambers. It has the grave. disadvantage that its efficiency rapidly falls 
off with the wear of the internal parts, and in metalliferous mines the wear- 
and-tear is severe, due to the large amount of grit in suspension in the water. 
When used as a stationary pump this disadvantage, however, can to a 
great extent be overcome by providing large settling-cisterns and efficient 
silt-traps ; but when used for the purpose of sinking it is not possible to 
do this, and convenience has to be purchased at the price of comparatively 
heavy repairs and loss of efficiency. 
The question of pumping has been dealt with more fully than some of the 
other departments in gold-mining because it is quite obvious that, given 
the case of a heavily watered mine, everything depends on an efficient 
pumping plant. The utilization of electricity for driving the pumps depends 
to a great extent on the cost of power, and on the means which can be 
adopted to render these pumps immune from flooding. Each individual 
case must be judged on its merits, but it may be stated roughly that, given 
