Pegasus
3 of the 6 encyclopedias on this shelf carry an entry for Pegasus. All 3 are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
in Greek legend, the winged horse of the Muses. He arose from the blood of the Gorgon Medusa when she was slain by Perseus. The myth of Pegasus is connected with that of Bellerophon. When the latter was considering how to meet the monster Chimaera, he was advised to sleep in the temple of Minerva. The goddess gave him a golden bridle, which, on awakening, he found controlled Pegasus. He mounted the steed and overcame the monster. Bellerophon became too much elated over his victory, so Jupiter sent a gadfly to sting Pegasus. The horse threw its rider, who became lame and blind in consequence. Hippocrene, the inspiring spring of the Muses on Mount Helicon, was created by a kick from the hoof of Pegasus. Longfellow follows a portion of the legend in his Pegasus in Pound.
1000 Classical Characters (1900)
A winged horse sprung from the blood of Medusa . According to Ovid he fixed his abode on Mount Helicon, where, by striking the earth with his foot, he raised a fountain which has been called Hippocrene .
Collier's New Encyclopedia (1921)
in astronomy, the Flying Horse; one of the 20 ancient N. constellations, bounded on the N. by Lacerta and Andromeda, on the S. by Aquarius, on the E. by Pisces, and on the W. by Equuleus and Delphinus. It is on the meridian in September at midnight. Alpha Pegasi is Markab, Beta Pegasi is Scheat, and Gamma Pegasi is Algenib. These with Alpha Andromedæ constitute the great square of Pegasus. In classical mythology, a winged steed which sprang forth from the neck of Medusa after her head had been severed by Perseus. As soon as he was born he flew upward, and fixed his abode on Mount Helicon, where, with a blow of his hoofs he produced the fountain Hippocrene. In ichthyology, the only genus of the family Pegasidæ. Pectoral fins broad, horizontal, long, composed of simple rays, sometimes spinous. Upper part of the snout produced. Four species are known; all very small fishes.
What Has Changed in the Last Century
The mythology in all three accounts still stands as classicists tell it; the divergence you can see on this page — Aiton's 1910 gadfly that leaves Bellerophon lame and blind, against the note that Zeus killed him outright — reflects genuinely competing ancient versions, not a later correction. What has moved is the sky. When Collier's called Pegasus "one of the 20 ancient N. constellations" in 1921, the modern scheme had not yet been fixed; the International Astronomical Union settled on 88 constellations with ruled boundaries in the 1920s, and Alpha Andromedae — Collier's fourth corner of the great square — was left on the Andromeda side of the line. In 1995 the star 51 Pegasi was found to have a planet, the first ever detected around a sun-like star, a discovery that won its finders the 2019 Nobel Prize in Physics.
Written for this edition, 2026.