art in the War. As a consequence the number of students
of science has greatly increased; manufacturing firms are awakening to
the fact that they must pay more attention to scientific development
and are founding research laboratories. It is very important that this
awakened attention should be well informed, and for that reason it
cannot be pointed out too often that the scientific work which has been
the basis of all material progress can only be turned to definite
material ends in the last stages of its development. Fundamentally
everything rests on the pure attempt to gain knowledge without any idea
of the use to which it may subsequently be put. Without pure science
there is no applied science at all. It is quite right in my opinion that
the researcher in pure science should have with him the hope that what
he does may one day be of direct benefit to others. But it is probable
that he does not in his own mind confine the idea of possible uses to
such material matters as I have mentioned above and as are so prominent
at present. He believes that his work has a less material side whose
value need not be explained to the present audience.

In the general line of progress it is natural to find that there are
certain broad roads along which the main advance has been directed.
Students of physics and chemistry and the subjects which are allied to
them find that they are in general considering either matter, or
electricity, or energy. I make this classification, not from any
philosophical point of view, but simply for present convenience. The
first important principle to which I would like to draw your attention
is that each of these things can be measured quantitatively. If we
accept the weight of a substance as an indirect measure of the amount of
matter present, then we all know we can express the amount of matter in
any given body in terms of a fundamental unit, like a pound or a gramme;
and the idea has been put to immemorial use. In later years we have
learnt that electricity itself is also a quantity and that the amount of
electricity which stands on an electrified body, or flows past a given
point in an electric conductor, as for example the wire connected to an
electric light, can be expressed arithmetically in terms of some unit.
Instruments are made for the purpose of measuring quantities of
electricity in terms of the legal standard. It is one of the functions
of a Government Institution, like the National Phys