PREFACE



photo-engraving, electrotyping, lithography, color printing,
and similar new methods of illustration.
   The modern study of light has resulted in other scientific
achievements of lasting importance, notably our knowledge
of the velocity of light, spectrum analysis, and the Roentgen
rays. In the study of medicine, to which this last invention
has been principally applied, a new era may be said to date
from the use of anesthetics and antiseptics, first adopted dur-
ing the middle of the last century. A similar impulse to the
theoretical study of medicine has been given by the discovery
of the functions of the blood corpuscles, the cell theory in
embryology, and the germ theory. Of like importance to
science are such scientific discoveries as the correspondence
between heat and energy; the theory of gases; of molecules
and of atmospheric dust; the nebular and meteoric theories
in astronomy; and the determination of geological epochs,
resulting indirectly in Dalwin's theory of the evolution of
species and the origin of man. War has been made more
terrible by such instruments of destruction as torpedoes,
rifled firearms, machine guns, smokeless powder, lyddite,
and melinite.
   So much for a single century's achievements in science.
They outnumber the great inventions of all the previous cen-
turies within historic times. The same may be said of some
other triumphs of the past century-notably of music. No
less has been accomplished in some other arts. The great
masterpieces in painting of the late Middle Ages and the
Renaissance have been rivaled in this century by the artists
of France, England and other modern schools.
   Unlike music and the fine arts, the march of modern lit-
erature has been along national lines. It was a far cry from
Haydn to Wagner, or from David to Millet, yet it seems
no further than the intervals of intellect that lie between
Keats and Kipling, Kant and Nietzsche, Schiller and Suder-
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