inst which it
strikes. In other words, the latter must not "smash" the jet, but must
run along with it. In the case of the windmill the ratio has been
stated approximately by the generalisation that the velocity of the
tips of the sails is about two and a half times that of the wind. This
refers to the old style of windmill as used for grinding corn.

The steam turbine must, therefore, be essentially a motor of very
great initial speed; and the efforts of recent inventors have been
wisely directed in the first instance to the object of applying it to
those purposes for which machinery could be coupled up to the motor
with little, if any, necessity for slowing down the motion through
such appliances as belting, toothed wheels, or other forms of
intermediate gearing. The dynamo for electric lighting naturally first
suggested itself; but even in this application it was found necessary
to adopt a rate of speed considerably lower than that which the steam
imparts to the turbine; and, unfortunately, it is exactly in the
arrangement of the gear for the first slowing-down that the main
difficulty comes in.

Nearly parallel is the case of the cream separator, to which the
steam-turbine principle has been applied with a certain degree of
success. By means of fine flexible steel shafts running in bearings
swathed in oil it has been found possible to utilise the comparatively
feeble force of a small steam jet operating at immense speed to
produce one of much slower rate but enormously greater strength. Some
success has been achieved also in using the principle not only for
cream separators, which require a comparatively high velocity, but for
other purposes connected with the rural and manufacturing industries.

An immense forward stride, however, was made when the idea was first
conceived of a steam-turbine and a water-turbine being fixed on the
same shaft and the latter being used for the propulsion of a vessel at
sea. In this case it is obvious that, by a suitable adjustment of the
pitch of screw adopted in both cases, a nice mathematical agreement
between the vapour power and the liquid application of that power can
be ensured.

All previous records of speed have been eclipsed by the turbine-driven
steamers engined on this principle. Through the abolition of the
principal causes of excessive vibration--which renders dangerous the
enlargement of marine reciprocating engines beyond a certain size--the
final limit of possible