Gustav Adolph Fidelie Van Rhyn, The American Cyclopædia (1879)
“ They concluded that there had been an age when men used only implements of stone and bone, and were ignorant of the use of metals; that an age had succeeded when the use of bronze was known, and probably that of gold; and that there was a third age, when iron had superseded other metals for weapons and utensils. All the finds were consequently classified according to these three ages. It proved, however, that such exact lines could not be maintained. Men did not immediately cease to use stone implements when bronze was introduced ”
