revolutionary in its effects upon society, as these later inventions which we have just named. To attempt to define them clearly is to enter the field of uncertainty, but two or three conjectures may be hazarded that cannot be very wide of the truth.

It is clear, for example, that if we go back in imagination to the very remotest ancestors of man that can be called human, we must suppose a vast and revolutionary stage of progress to have been ushered in by

the first race of men that learned to make habitual use of the simplest implement, such as a mere club. When man had learned to wield a club and to throw a stone, and to use a stone held in the hand to break the shell of a nut, he had attained a stage of culture which augured great things for the future. Out of the idea of wielded club and hurled stone were to grow in time the ideas of hammer and axe and spear and arrow.

Then there came a time-no one dare guess how many thousands of years later-when man learned to cover his body with the skin of an animal, and thus to become in a measure freed from the thraldom of the weather. He completed his enfranchisement by learning to avail himself of the heat provided by an artificial fire. Equipped with these two marvelous inventions he was able to extend the hitherto narrow bounds of his dwelling-place, passing northward to the regions which at an earlier stage of his development he dared not penetrate. Under stress of more exhilarating climatic conditions, he developed new ideals and learned to overcome new difficulties; developing both a material civilization and the advanced mentality

that is its counterpart, as he doubtless never would have done had he remained subject to the more pampering conditions of the tropics.

The most important, perhaps, of the new things which he was taught by the seemingly adverse conditions of an inhospitable climate, was to provide for the needs of a wandering life and of varying seasons by domesticating animals that could afford him an ever-present food supply. In so doing he ceased to be a mere fisher and hunter, and became a herdsman. One other step, and he had conceived the idea of providing for himself a supply of vegetable foods, to take the place of that which nature had provided so bountifully in his old home in the tropics. When this idea was put into execution man became an agriculturist, and had entered upon the high road to civilization.

All these stages of progress had been entered upon prior to the time of which the oldest known remains of the cave-dweller give us knowledge. It were idle to conjecture the precise sequence in which these earliest steps toward civilization were taken, and even more idle to conjecture the length of time which elapsed between one step and its successor. But all questions of precise sequence aside, it is clear that here were four or five great ages succeeding one to another, that marked the onward and upward progress of our primeval ancestor before he achieved the stage of development that enabled him to leave permanent records of his existence. And what is particularly significant from our present standpoint-it is equally clear that each of the great ages thus vaguely outlined was

dependent upon an achievement or an invention that facilitated the carrying out of that scheme of neverending work which from first to last has been man's portion. How to labor more efficiently, more productively; how to produce more of the necessaries and of the luxuries that man's physical and mental being demands, with less expenditure of toil-that from first to last has been the ever-insistent problem. And the answer has been found always through the development of some new species of mechanism, some new labor-saving device, some ingenious manipulation of the powers of Nature.

If, turning from the hypothetical period of our primitive ancestor, we consider the sweep of secure and relatively recent history, we shall find that precisely the same thing holds. If we contrast the civilization of Old Egypt and Babylonia-the oldest civilizations of which we have any secure record-with the civilization of to-day, we shall find that the differences between the one and the other are such as are due to new and improved methods of accomplishing the world's work.

Indeed, if we view the subject carefully, it will become more and more evident that the only real progress that the historic period has to show is such as has grown directly from the development of new mechanical inventions. The more we study the ancient civilizations the more we shall be struck with their marvelous resemblance, as regards mental life, to the civilization of to-day. In their moral and spiritual ideals, the ancient Egyptians were as brothers to the modern Europeans. In philosophy, in art, in literature, the

Age of Pericles established standards that still remain unexcelled. In all the subtleties of thought, we feel that the Greeks had reached intellectual bounds that we have not been able to extend.

But when, on the other hand, we consider the material civilization of the two epochs, we find contrasts that are altogether startling. The little world of the Greeks nestled about the Mediterranean, bounded on every side at a distance of a few hundred leagues by a terra incognita. The philosophers who had reached the confines of the field of thought, had but the narrowest knowledge of the geography of our globe. They traversed at best a few petty miles of its surface on foot or in carts; and they navigated the Mediterranean Sea, or at most coasted out a little way beyond the Pillars of Hercules in boats chiefly propelled by oars. By dint of great industry they produced a really astonishing number of books, but the production of each one was a long and laborious task, and the aggregate number indited during the Age of Pericles in all the world was perhaps not greater than an afternoon's output of a modern printing press.

In a word, these men of the classical period of antiquity, great as were their mental, artistic, and moral achievements, were as children in those matters of practical mechanics upon which the outward evidences of civilization depend. Should we find a race of people to-day in some hitherto unexplored portion of the earth-did such unexplored portions still existliving a life comparable to that of the Age of Pericles, we should marvel no doubt at their artistic achievements,

while at the same time regarding them as scarcely better than barbarians. Indeed this is more than unsupported hypothesis; for has it not been difficult for the Western world to admit the truly civilized condition of the Chinese, simply because that highly intellectual race of Orientals has not kept abreast of the Occidental changes in applied mechanics? Say what we will, this is the standard which we of the Western world apply as the test of civilization.

If, sweeping over in retrospect the history of the world since the time when the Egyptian and Babylonian civilizations were at their height, we attempt some such classification of the stages of progress as that which we a moment ago applied to pre-historic times, we shall be led to some rather startling conclusions. In the broadest view, it will appear that the age which ushered in the historic period continued unbroken by the advance of any great revolutionary invention throughout the long centuries of pre-Christian antiquity, and well into the so-called Middle Ages of our newer era. Then came the invention of gunpowder, or at least its introduction to the Western world-since the Chinaman here lays claim to vague centuries of precedence. Following hard upon the introduction of gunpowder, with its capacity to add to the destructive efficiency of man's most sinister form of labor, came a mechanism no less epoch-making in a far different field-the printing press.

But even these inventions, great as was their influence upon the progress of civilization, can scarcely be considered, it seems to me, as taking rank with the