Byzantium
2 of the 7 encyclopedias on this shelf carry an entry for Byzantium. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a city on the Thracian Bosporus, founded by emigrants from Megara in 667 B. c. It rose rapidly to importance as a seat of commerce, was subject to the Persians (515-478 b. c.), was freed by Pausanias, and was alternately Athenian and Lacedæmonian during the Peloponnesian War. Thrasybulus expelled the Spartans in 390, and the city long enjoyed a kind of independence. It was taken by Severus in 196 A. D., and in 330, under the name of New Rome or Constantinople, it was made the metropolis of the Roman Empire. C, in Anglo-Saxon, was taken directly from the Latin alphabet, the source, it is believed , whence it has passed into various languages. In English words immediately derived from Anglo-Saxon, the c of the Anglo -Saxon often becomes k in English, as A. S. cyng Eng. king; A. S. cyn Eng. kin, or kindred. Sometimes the A. S. c becomes q in English, as A. S. Cwen-Eng. queen. At others it is changed into ch, as A. S. cild-Eng. child. In modern English c has two leading values. Before i and e it is sounded as s (examples: certain, cincture), and before a, o, and u as k (examples: cat, cost, curtly). It is mute before k, as trick. C. As an initial is used: 1. In chronology: Chiefly for Christ, as B. C. (Before Christ). 2. In Music: For counter-tenor, or contralto. 3. In university degrees: For Civil, as D. C. L. Doctor of Civil Law. C. As a symbol is used: 1. In numerals: For 100. Thus CII= 102, CC-200. 2. In chemistry: For the element carbon, of which it is also the initial letter. 3. In music: (1) For the first note of the diatonic scale, corresponding to do of the Italians. (2) For the natural major mode, that in which no sharps or flats are employed. (3) For common or four-crochet time.
Aiton's Encyclopedia (1910)
bi-zan' shi-um, a Greek city on the Bosporus. Constantine the Great enlarged it greatly, changed its name to Constantinople, and made it the capital of the Roman Empire (324 A. D.). At the division of the Roman Empire Byzantium became the seat of the Eastern, the Greek, and the Byzantine Empire, as it was variously called. The term Byzantine occurs frequently in connection with the churches, the art, literature, emperors, and the government of the East. Byzantine art is noted for an oriental luxuriance and coloring. In architecture the principal feature of note is the success with which round domes are supported on square bases, as in the church of St. Sophia at Constantinople and in the Cathedral of St. Mark at Venice. See Constantinople