Author of "Color and Its Applications," "Light and Shade
and Their Applications," "The Lighting Art,"
"The Language of Color," etc.

_ILLUSTRATED WITH
PHOTOGRAPHS_



NEW YORK
THE CENTURY CO.
1920

Copyright, 1920, by
THE CENTURY CO.




DEDICATED

TO THOSE WHO HAVE ENCOURAGED
ORGANIZED SCIENTIFIC RESEARCH FOR
THE ADVANCEMENT OF CIVILIZATION




PREFACE