Question

OILS
There are three main groups of oils: animal, vegetable and mineral.
Great quantities of animal oil come from whales, those enormous creatures
of the sea which are the largest remaining animals in the world. To protect
the whale from the cold of the Arctic seas, nature has provided it with a
thick covering of fat called blubber. When the whale is killed, the blubber is
stripped off and boiled down, either on board ship or on shore. It produces a
great quantity of oil which can be made into food for human consumption. A
few other creatures yield oil, but none so much as the whale. The livers of
the cod and the halibut, two kinds of fish, yield nourishing oil. Both cod liver
oil and halibut liver oil are given to sick children and other invalids who need
certain vitamins. These oils may be bought at any chemist's.
Vegetable oil has been known from antiquity. No household can get on
without it, for it is used in cooking. Perfumes may be made from the oils of
certain flowers. Soaps are made from vegetable and animal oils.
To the ordinary man, one kind of oil may be as important as another.
But when the politician or the engineer refers to oil, he almost always means
mineral oil, the oil that drives tanks, aeroplanes and warships, motor-cars
and diesel locomotives; the oil that is used to lubricate all kinds of
machinery. This is the oil that has changed the life of the common man.
When it is refined into petrol it is used to drive the internal combustion
engine. To it we owe the existence of the motorcar, which has replaced the
private carriage drawn by the horse. To it we owe the possibility of flying. It
has changed the methods of warfare on land and sea. This kind of oil comes
out of the earth. Because it burns well, it is used as fuel and in some ways it
is superior to coal in this respect. Many big ships now burn oil instead of
coal. Because it burns brightly, it is used for illumination; countless homes
are still illuminated with oil-burning lamps. Because it is very slippery, it is
used for lubrication. Two metal surfaces rubbing together cause friction and
heat; but if they are separated by a thin film of oil, the friction and heat are
reduced. No machine would work for long if it were not properly lubricated.
The oil used for this purpose must be of the correct thickness; if it is too thin
it will not give sufficient lubrication, and if it is too thick it will not reach all
parts that must be lubricated.​

Answer 1

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