lso if we could find in the lowest layer certain relics of the human
race, we could know that the race lived at that time. If we should
find relics later on of a different nature, we should be able to
estimate the progress of civilization.

The second method is of (2) _paleontology_, which is developed along
with geology. In this we have both the vertebrate and invertebrate
paleontology, which are divisions of the science which treats of
ancient forms of animal and vegetable life. There are many other
divisions of paleontology, some {61} devoting themselves entirely to
animal life and others to vegetable, as, for instance, paleobotany. As
plants and animals have gradually developed from lower to higher forms
and the earth has been built gradually by formations at different
periods of existence, by a comparison of the former development with
the latter, that is, comparison with the earth, or inorganic,
development to the life, or organic, development, we are enabled to get
a comparative view of duration. Thus, if in a layer of earth,
geological time is established and there should be found bones of an
animal, the bones of a man, and fossilized forms of ancient plants, it
would be easy to determine their relative ages.

The third method is that of (3) _anatomy_, which is a study of the
comparative size and shape of the bones of man and other animals as a
method of showing relative periods of existence. Also, just as the
structure of the bones of a child, as compared with that of a man,
would determine their relative ages, so the bones of the species that
have been preserved through fossilization may show the relative ages of
different types of animals. The study of the skeletons of animals,
including those of man, has led to the science of anthropometry.

The fourth method is to study the procession of man by (4) _cultures_,
or the industrial and ornamental implements that have been preserved in
the river drift, rocks, and caves of the earth from the time that man
used them until they were discovered. Just as we have to-day models of
the improvement of the sewing-machine, the reaper, or the
flying-machine, each one a little more perfect, so we shall find in the
relics of prehistoric times this same gradual development--first a
stone in its natural state used for cutting, then chipped to make it
more perfect, and finally beautified in form and perfected by polishing.

Thus we shall find progress from the natural