FROM geometry we proceeded to the larger
science of kinematics, which includes ge-
ometrical measurements and measurements of
time as well. Just as we employ geometry in the
practice of mensuration without regard to the
composition or the intrinsic properties of the
objects measured, so in kinematics we are deal-
ing with the laws of abstract motion without
caring what it is that moves. If we now wish to
enlarge this science still further, so as to in-
clude not only space and time, but some other
measured quantity, we seek among the count-
less properties of natural objects some one
property which they all possess and which seems
suitable for the purpose. The property so
chosen by the pioneers in science is the one we
now call mass, and the general science which
results is called mechanics.

The choice was by no means compulsory.
Electric charge, for example, is a very impor-
tant property, and the great science of electro-
magnetics can be built up out of the concept
of space and time and electric charge without

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