ways of setting about the same work, and, in
order that he may choose the best, the labourer must be intelligent and
skilful, or else he must be directed by some person who has knowledge
and skill. Moreover, there must be, as we shall see, great division of
labour, so that each man shall do the kind of work he can do best. We
need, then--

(1) #Science#,
(2) #Division of labour#.

#24. The Need of Science.# In order that he may employ his labour to the
best advantage, it is requisite that the labourer should be not merely
skilful, that is, clever, and practised in handiwork, but that he should
also be guided by a scientific knowledge of the things with which he is
dealing. Knowledge of nature consists, to a great extent, in
understanding the #causes of things#, that is, in knowing what things
must be put together in order that certain other things shall be
produced. Thus the steam-engine is due to the discovery that if heat be
applied to water, the result is steam expanding with much force, so that
a firebox, coal, boiler, and water are causes of force. Whenever we want
to do any work, then, we must begin by learning, if possible, what are
the causes which will produce it most easily and abundantly. By
knowledge we shall often be saved from much needless labour.

As Sir John Herschel has explained, science sometimes shows us that
#things which we wish to do are really impossible#, as, for instance, to
invent a perpetual motion, that is, a machine which moves itself. At
other times science teaches us that the #way in which we are trying to
make something is altogether the wrong way#. Thus, iron-masters used to
think that the best way of smelting iron in the blast-furnace was to
blow the furnace with cold air; science, however, showed that, instead
of being cold, the air sent into the furnace should be made as hot as
possible. Then, again, science often enables us #to do our work with a
great saving of labour#. The boatman or bargeman takes care to learn the
state of the tide, so that he may have the tide in his favour in making
any journey. Meteorologists have now prepared maps of the oceans showing
the sea-captain where he will find winds and currents most favourable to
a rapid voyage. Lastly, #science sometimes leads us to discover
wonderful things which we should not have otherwise thought it possible
to do#; it is sufficient to mention the discovery of photography and the
invention of the telegraph and the telep