[Illustration: Triumphal Procession from the Arch of Titus] But the Eastern Empire stood, and Constantinople was its capital. And it stood, alone and unassisted, as the sole bulwark of Christianity and civilization for nearly 1000 years, until it finally fell before the Ottoman Turks in 1543. It could not have done this, if in the latter part of the seventh century when it was beleaguered by a Turkish fleet, much greater than its own, it had not suddenly received unexpected aid in the shape of a new invention. This was "Greek fire," which seems to have been a pasty mixture of sulphur, nitre, pitch, and other substances, which when squirted against wood set it on fire with a flame that water could not quench. In the very first attack, the Turks were so demoralized by the Greek fire that they fled in panic. They never learned the secret and were never able to stand up against it. On one occasion, fifteen Christian ships, using Greek fire, actually put to rout a Turkish fleet numbering several hundred. * * * * * During all the countless centuries before the dawn of recorded history, and during the approximately forty centuries that elapsed from the beginning of recorded history until the fall of Rome, we have observed the coming of many inventions of both material and immaterial kinds, and noted the influence of those inventions in causing civilization, and therefore in directing the line that history has followed. It may be objected that a perfectly natural inference from what has been written would be that the only thing which had influenced the direction of movement of history was invention. To this, the answer may very reasonably be made that this book does not pretend to be a history, or to point out what have been the greatest factors that have influenced its line of movement; it attempts merely to emphasize the influence of one factor, invention, and to suggest that maybe its influence has not hitherto been estimated at its proper value. Another objection like that just indicated might be made to the effect that all the progress of the world up to the fall of Rome is attributed in this book to inventors only; that all the work of statesmen, scientists, generals, admirals, explorers, jurists, men of business, etc., etc., is ignored. Such an objection would be natural and reasonable; but to it an answer like the previous one may be made, to the effect that the purpose of this book is not to compare the benefits conferred by any one class of men with those conferred by any other, but merely to point out, in a very general way, what inventors have done.