HŌRŎLŎGĬUM

( ὡρολόγιον ), the name of the various instruments by means of which the ancients measured the time of the day and night. The earliest and simplest horologia of which mention is made, were called polos ( πόλος ) and gnomon ( γνώμων ). Both divided the day into twelve equal parts, and were a kind of sun-dial. The gnomon , which was also called stoic he i on ( στοιχεῖον ), was the more simple of the two, and probably the more ancient. It consisted of a staff or pillar standing perpendicular, in a place exposed to the sun ( σκιάθηρον ), so that the length of its shadow might be easily ascertained. The shadow of the gnomon was measured by feet, which were probably marked on the place where the shadow fell. In later times the name gnomon was applied to any kind of sun-dial, especially to its finger which threw the shadow, and thus pointed to the hour. The polos or helio trop i on ( ἡλιοτρόπιον ), on the other hand, seems to have been a more perfect kind of sun-dial; but it appears, neverthele , not to have been much used. It consisted of a basin ( λεκανίς ), in the middle of which the perpendicular staff or finger ( γνώμων ) was erected, and in it the twelve parts of the day were marked by lines.—Another kind of horologium, was the clepsydra ( κλεψύδρα ). It derived its name from κλέπτειν and ὕδωρ , as in its original and simple form it consisted of a ve el with several little openings ( τρυπήματα ) at the bottom, through which the water contained in it escaped, as it were by stealth. This instrument seems at first to have been used only for the purpose of measuring the time during which persons were allowed to speak in the courts of justice at Athens. It was a hollow globe, probably somewhat flat at the top-part, where it had a short neck ( αὐλός ), like that of a bottle, through which the water was poured into it. This opening might be closed by a lid or stopper ( πῶμα ), to prevent the water running out at the bottom. As the time for speaking in the A then i an courts was thus measured by water, the orators frequently use the term ὕδωρ instead of the time allowed to them. An especial officer ( ὁ ἐφ’ ὕδωρ ) was appointed in the courts for the purpose of watching the clepsydra, and stopping it when any documents were read, whereby the speaker was interrupted. The time, and consequently the quantity of water allowed to a speaker, depended upon the importance of the case. The clepsydra used, in the courts of justice was, properly speaking, no horologium; but smaller ones, made of gla , and of the same simple structure, were undoubtedly used very early in families for the purposes of ordinary life, and for dividing the day into twelve equal parts. In these gla -clepsydrae the division into twelve parts must have been visible, either on the gla globe itself, or in the basin into which the water flowed.—The first horologium with which the Romans became acquainted was a sun-dial ( solarium or horologium sci other i cum ), and was said to have been brought to Rome by Papirius Cursor twelve years before the war with Pyrrhus. But as sun-dials were usele when the sky was cloudy, P. Scipio Nasica, in his censorship, 159 B.C. , established a public clepsydra, which indicated the hours both of day and night. This clepsydra was in after times generally called solarium. After the time of Scipio Nasica several horologia, chiefly solaria, seem to have been erected in various public places at Rome. Clepsydrae were used by the Romans in their camps, chiefly for the purpose of measuring accurately the four vigiliae into which the night was divided. The custom of using clepsydrae as a check upon the speakers in the courts of justice at Rome, was introduced by a law of Cn. Pompeius, in his third consulship. Before that time the speakers had been under no restrictions, but spoke as long as they deemed proper. At Rome, as at Athens, the time allowed to the speakers depended upon the importance of the case.