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a store of oil； petroleum； or naphtha in cans； from which to replenish the
oil tank of the carriage on the journey； if it be a long one。
〃Can it be easily driven？ We cannot say that such a vehicle would be
suitable for a lady； unless rubber…tyred wheels and other improvements are
made to the carriage； for a grim grip of the steering handle and a keen eye
are necessary for its safe guidance； more especially if the high road be
rough。 It never requires to be fed； and as it is； moreover； unsusceptible of
fatigue； it is obviously the sort of vehicle that should soon achieve a
widespread popularity in this country。
〃It is a splendid hill climber； and； in fact； such a hill as that of Priest
Hill （a pretty good test of its capabilities） shows that it climbs at a faster
pace than a pedestrian can walk。
〃A trip from Rosenau to Old Windsor； to the entrance of Beaumont
College； up Priest Hill； descending the steep； rough； and treacherous hill
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on the opposite side by Woodside Farm； past the workhouse； through old
Windsor； and back to Rosenau within an hour； amply demonstrated how
perfectly under control this carriage is； while the sensation of being
whirled rapidly along is decidedly pleasing。〃
Another pioneer of motorism was the Hon。 C。 S。 Rolls； whose
untimely death at Bournemouth in 1910； while taking part in the
Bournemouth aviation meeting； was deeply deplored all over the country。
Mr。 Rolls made a tour of the country in a motor…car in 1895； with the
double object of impressing people with the stupidity of the law with
regard to locomotion； and of illustrating the practical possibilities of the
motor。 You may know that Mr。 Rolls was the first man to fly across the
Channel； and back again to Dover； without once alighting。
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CHAPTER XXI The Internal…combustion
Engine（Cont。）
I suppose many of my readers are quite familiar with the working of a
steam…engine。 Probably you have owned models of steam…engines right
from your earliest youth； and there are few boys who do not know how the
railway engine works。
But though you may be quite familiar with the mechanism of this
engine； it does not follow that you know how the petrol engine works； for
the two are highly dissimilar。 It is well； therefore； that we include a short
description of the internal…combustion engine such as is applied to motor…
cars； for then we shall be able to understand the principles of the aeroplane
engine。
At present petrol is the chief fuel used for the motor engine。 Numerous
experiments have been tried with other fuels； such as benzine； but petrol
yields the best results。
Petrol is distilled from oil which comes from wells bored deep down
in the ground in Pennsylvania； in the south of Russia； in Burma； and
elsewhere。 Also it is distilled in Scotland from oil shale； from which
paraffin oil and wax and similar substances are produced。 When the oil is
brought to the surface it contains many impurities； and in its native form is
unsuitable for motor engines。 The crude oil is composed of a number of
different kinds of oil； some being light and clear； others heavy and thick。
To purify the oil it is placed in a large metal vessel or 〃still〃。 Steam is
first passed over the oil in the still； and this changes the lightest of the oils
into vapours。 These vapours are sent through a series of pipes surrounded
with cold water； where they are cooled and become liquid again。 Petrol is
a mixture of these lighter products of the oil。
If petrol be placed in the air it readily turns into a vapour； and this
vapour is extremely inflammable。 For this reason petrol is always kept in
sealed tins； and very large quantities are not allowed to be stored near
large towns。 The greatest care has to be exercised in the use of this
〃unsafe〃 spirit。 For example； it is most dangerous to smoke when filling a
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tank with petrol； or to use the spirit near a naked light。 Many motor…cars
have been set on fire through the petrol leaking out of the tank in which it
is carried。
The tank which contains the petrol is placed under one of the seats of
the motor…car； or at the rear； if in use on a motor…cycle it is arranged along
the top bar of the frame； just in front of the driver。 This tank is connected
to the 〃carburettor〃； a little vessel having a small nozzle projecting
upwards in its centre。 The petrol trickles from the tank into the carburettor；
and is kept at a constant level by means of a float which acts in a very
similar way to the ballcock of a water cistern。
The carburettor is connected to the cylinder of the engine by another
pipe； and there is valve which is opened by the engine itself and is closed
by a spring。 By an ingenious contrivance the valve is opened when the
piston moves out of the cylinder； and a vacuum is created behind it and in
the carburettor。 This carries a fine spray of petrol to be sucked up through
the nozzle。 Air is also sucked into the carburettor； and the mixture of air
and petrol spray produces an inflammable vapour which is drawn straight
into the cylinder of the engine。
As soon as the piston moves back； the inlet valve is automatically
closed and the vapour is compressed into the top of the cylinder。 This is
exploded by an electric spatk； which is passed between two points inside
the cylinder； and the force of the explosion drives the piston outwards
again。 On its return the 〃exhaust〃 or burnt gases are driven out through
another valve； known as the 〃exhaust〃 valve。
Whether the engine has two； four； or six cylinders； the car is propelled
in a similar way for all the pistons assist in turning one shaft； called the
engine shaft； which runs along the centre of the car to the back axle。
The rapid explosions in the cylinder produce great heat； and the
cylinders are kept cool by circulating water round them。 When the water
has become very hot it passes through a number of pipes