it is set down at just what place each train must be at each moment of every day, and the safety of lives and property depends on exact adherence to the prescribed order, then the station clocks must be invariable and synchronous and the conductor's watch true to the second. Civilization is marked at every step of its progress by the multiplication of the varied relations between men, and since the importance of time is enhanced by the same multiplication it may fairly be asked whether the accuracy with which time is observed in ordinary life may not after all afford one of the most perfect indications of the social condition of a people.

The material is not gathered for a full discussion of a question like this, and I shall not occupy myself with it, but as incidental to and suggested by the topic I have chosen some light seems to be thrown on it by the attempt to place in their true correlation facts of history not hitherto brought together. I have proposed to myself only a study of the growth of the common clock, noting the various steps in its development with reference to their period in history and to the social conditions which inspired or demanded them as well as to the state of science and mechanic arts which made their consummation possible. The subject is too large for a single paper, and I have therefore taken for present consideration that part which relates to time-keeping among the ancient peoples from whom we chiefly derive our civilization and to a period of history which, by a sort of coincidence, practically terminates with the beginning of our era. My guide in this inquiry will be the principles in eurematics that inventions always spring from prior inventions or known expedients, and that they come in response to recognized wants. It need not be repeated that these principles, find copious illustrations in the progress of every art; but the truth cannot be too strongly enforced that the progress of no art can be intelligently studied or thoroughly comprehended without keeping them in mind.

The few barren and isolated facts that have been preserved to us regarding time-keeping prior to about 600 years ago are not enough in themselves, however carefully collated, to constitute an intelligible or consecutive history. But I need not say that no event is in fact isolated from all others in cause and effect; and if we cannot have direct light we may look to the concurrent events of history for side lights upon our meager facts which will, perhaps, throw them into stronger relief than the direct narration of unphilosoph

ical historians. Hence, if I shall seem to any one to lean too much upon the synchronisms and sequences of history, it is not that I do not realize the possible fallaciousness of an argument which has no other foundation; but in the progress of inventions such sequences are to be sought for. Invention responds to want, and the want may originate in some crisis or event having no apparent affinity in character with the want it engendered or the invention that sprang to meet it. And these are not mere accidents: they are the natural course of what I venture to call the fixed laws of eurematics. At the same time these laws do not necessarily always call for original invention, since importation of an invention already known elsewhere may equally supply the want, and historical crises are as likely to lead to importation, where it is possible, as to invention. It is with these principles in view, and always looking for such side light as contemporary events can give, that I have attempted to frame the consecutive history of time-keeping, of which this paper is a part.

There are three primitive forms of time-keeping instrumentsthe sun-dial, the clepsydra or water clock, and the graduated candle. The last plays no part in the evolution of the modern time-keeper, and I shall pass it by without further notice, notwithstanding some interesting historical associations connected with it. But the sundial was at the beginning the only time-keeper, and man's ideas, developing into wants, led to its greater perfection till these wants passed far beyond what, with its limitations, it could supply. Its contribution to the present state of the art was not large, mechanically considered, but it was enough to create the demand for something better, and without this contribution the art could not have been. The rude utensil which the Greeks called a clepsydra had no resemblance to the perfected time-piece of this century, but nothing in history is surer than that out of it, by slow accretions, science and art, by turns mistress and handmaid, have produced the masterpiece of both.

This history is, therefore, the history of a human want and of a mechanical structure developed in response to it. But wants grow, and this has grown; and in tracing it we do not find it always in the same likeness. Sometimes the want of the moment is satisfied, and then it appears in a novel and unexpected form, altered in its whole complexion by that which has just appeased it. And as we recognize this Protean character, we need not suppose that the

Babylonian astrologer who made some improvement in a sun-dial had a single idea or purpose in common with those of a railway manager who last week connected his regulator by wire with the Observatory. We trace our want in the development of institutions, in the creation of new demands upon time, in the growing complexity of human relations, in political crises, and we may determine its character or intensity by the means used to supply it and the generality of their adoption. The story of the growth of the instrument is inseparable from that of the growth of civilization.

Writers on the history of the clock (and they are not few) have generally begun by a reference to the sun-dial as a Babylonian or Chaldean invention. We can trace it no further, and have no means of determining when the invention was made. We learn from the Old Testament Scriptures that it was known at Jerusalem as early as seven centuries before our era, and the manner of its mention indicates that in that city it was a novelty. King Ahaz, by whose name this dial is called, had introduced other novelties into his capital on his return from Damascus, whither he had gone to make his submission to Tiglath-Pileser II, King of Assyria; and it is not unreasonable to suppose that the dial had the same origin. However this may be, it was a graduated instrument, having degree marks of some kind which showed the daily course of the sun. We may infer that it was at least of a Babylonian pattern, and it points to a remote period when a graduated dial indicating the time of day by a shadow passing over it was known to Oriental peoples.

Presumably it was their invention. The suggestion that they derived it from Egypt is a guess only, based on the supposed earlier growth of Egyptian science. To such a guess might be opposed the fact that in all the Egyptian monuments yet explored there is no hint of such an instrument.

The Assyrian monuments are equally silent; and the same speculation which attempts to account for the absence of all representation of a sun-dial in the sculptures which have revealed to us so much of the domestic life of the Assyrian people applies to Egypt also. We may believe that it was not a device generally known or commonly used. Very likely the knowledge of it was confined to the priests and magi, who were not only ministers of the religion. of each country but the masters of its science. This device constituted a part of their mystery and was religiously kept from the public knowledge. In support of this conjecture it may be said

that the Phoenicians, who penetrated every land, dealt in every merchantable commodity, and from their active commercial habits were the very persons who would have found the use of a time-piece most valuable, do not appear to have known of any such instrumentality; but the inner temples of Thebes and Babylon were not open to those hardy mariners, and the exhumations of Cyprus reveal no more to us than those of Nimroud and Memphis.

It is scarcely profitable to grope in the darkness for the origin of the sun-dial; but certain facts are apparent and may be briefly indicated. In Egypt and Assyria observation of the heavenly bodies was a part of the religious cult. The regulation of the calendar belonged to the ministers of religion. For the regulation of the calendar, which of course involved the determination of the length of the year, the recurrence of the solstices must be noted; and these could only be noted by observation of the day when the shadow cast by the sun at noon was at its maximum or minimum. The ob servation of shadows for the determination of noon led (it could scarcely be avoided) to their further observation during the entire period of the sun above the horizon, and, at last, to marking the surface on which the shadow was cast by permanent lines dividing the day into some kind of regular parts. All this might be done as a matter of scientific observation without conscious need of a timepiece.

The sun-dial took many forms, and more than one of these may have been known to the Babylonians. The art of dialing involved. mathematical problems of considerable complexity, and the study of this art very likely contributed to the knowledge of mathematics that the world possessed at that early period. The consideration of these forms is not germane to my present purpose, which is for the moment only to show that long before the appearance of the sun-dial in Greece the instrument had been apparently perfected by the wise men of the East.

Historians have agreed in fixing the period of the introduction of the sun-dial into Greece in the latter part of the sixth century B. C. Herodotus says it was derived from the Babylonians, from whom he also declares the Greeks to have derived the twelve parts (deza pea) of the day. Others, however, ascribe its invention to Anaximander, who is said to have set it up in Lacedæmon. It is evident that he need not have invented it, but might have brought it from some country where its use was already known. It is signifi

cant that Anaximander and Anaximenes (to whom some writers ascribe the honor of the invention), were both fellow citizens and pupils of Thales of Miletus, and that the date of this introduction. synchronizes with the extensive and intimate acquaintance between Egypt and Greece, which, commencing in the reign of Psammetichus, reached its culmination under Amasis, the fourth king of that dynasty, and in which the people of Miletus bore the most prominent part. Under this last king, whom they assisted in throwing off the yoke of Assyria, Greeks swarmed in the Egyptian court, filled her armies, manned her fleets. They passed to and fro continually; Greek philosophers pursued their studies in Egyptian schools; and who shall say how many of the secrets of art and science found their way at that time from the land of the Pharaohs to the spirited and versatile people just emerging from barbarism across the Mediterranean? Surely, if under such conditions anything of Egyptian origin or likely to have been in Egyptian possession is found to have made its appearance among the Greeks, we need not speculate as to how it got there.

It does not appear that the sun-dial was introduced to the Greeks in any perfected form. On the contrary, it was at first a mere staff or pillar (p), destitute of any graduated dial which could indicate the passage of an hour or any definite fraction of a day. The length of the shadow, measured in feet, determined the time for certain regular daily duties, as a shadow six feet long indicated the hour for bathing and one twelve feet long that for supper. More accurate and convenient forms were perhaps known to philosophers; but, if so, they did not come into common use. This simple device was sufficient for the simple habits of the people. The twelve parts of the day of which Herodotus speaks had no meaning to the Athenians, who had no word meaning specifically an hour; and as late as the time of Alexander, the old system seems to have been followed. This kind of observation, it may be remarked, was perfectly feasible in the shadow of an Egyptian obelisk, which may partly account for the absence of the instrument from other monuments of that country. As a matter of history, an obelisk at Rome was actually used for a sun-dial in the time of Augustus.

We learn from this history. at what period and in what stage of progress the Greeks first had the idea of measuring time. If we associate it with the period of Solon, the Athenian law-giver who died about 570 B. C., we may form some idea of the condition of