The duodecimal system of notation has been supplanted for many purposes by the more convenient decimal system, the invention of which is attributed by some to the Arabs; but the duodecimal divisions of time are still with us, and the duodecimal divisions of the circle are still used in most countries. The duodecimal system of notation seems to have been the earliest system of notation invented; and it was an invention so important that we cannot imagine civilization without it and the decimal system, possibly its offspring. The influence of these two inventions on history has been so great that the mind is incapable of realizing its greatness, even approximately. Who were the inventors, we do not know. It is almost certain that none of our generation ever will know, and it is far from probable that any one of any generation will ever know. If any knowledge on this subject is ever given to the world, it will be knowledge of names only--only names. Yet some human beings, forgotten now and probably obscure even in their lifetimes, invented those systems, and contributed more to the real progress of the race than many of the great statesmen and warriors of history. The Babylonians invented measures of length, capacity and weight, also; and it is from those measures that all the later measures have been directly or indirectly derived. To have invented systems by which time, angle, distance, space, weight and volume were lifted out of the realm of the vague and formless into the realm of the definite and actual, was an achievement that almost suggests that noted in the first chapter of Genesis, in the words, "And God said 'Let there be light,' and there was light"; for what a clearing up of mental darkness followed, when the science of measurement turned its rays on the mysteries that beset the path of early man! The Egyptians seem to have been inventors, though hardly to the same degree as were the Babylonians. The Egyptians studied the heavens and employed a science of astronomy; and it is possible that they, rather than the Babylonians, should be credited with its invention. But it is not the intention of this book to decide points in dispute in history, or even to discuss them. Its intention is merely to study the influence that inventions and inventors had. Whether the name of an inventor was John Smith or Archimedes, whether he lived in the year 1000 or 1100, or which one of two rival claimants should be credited with the honor of any invention, is often an interesting question; but it is not one that is especially important to us, unless it casts light on the main suggestion of our inquiry. The only reason for mentioning names and dates and countries in this book is to show the sequence of inventions as correctly as practicable. In order to show the influence of invention on history it seems best to give the treatment of the subject an historical character.