Alectryomancy, [1] divination, which was accomplished by means of a rooster. See Divination. This word is Greek, composed of ἀλεκτρυὼν, a rooster , and μαντεία, divination . 

This art was used by the Greeks, who practiced it in this way: they drew a circle on the ground, and then divided it into twenty-four equal portions or spaces, in each of which they depicted a letter of the alphabet, and on each letter they placed a seed of barley or wheat. This done, they placed in the middle of the circle a rooster prepared for this purpose, they carefully observed the letters from which the rooster removed the seeds, and from those gathered letters they formed a word that was the response to what they wanted to know. 

It was in this way that a few diviners named Fidustius, Irenaeus, Pergamius,  [2] and Hilarius, according to Ammianus Marcellinus, [3] to which Zonaras [4] adds Libanius and Jamblicus , [5] sought to discover who should be the successor to Emperor Valens. [6] The rooster having taken the seeds on the letters Θ, Ε, Ο, Δ, they thus concluded that it would be Theodorus : but it was Theodosius , who alone avoided Valens’s search; because this Prince, informed of the diviners’ actions, arranged the killing of all those whose names started with these first four letters, like Theodosius, Theodore, Theodat, Theodulus , along with the diviners. Hilarius, one of the latter, confessed in his interrogation, reported by Zonaras and quoted by Delrio, that they had, in truth, sought to find who would be Valens’s successor, not by alectryomancy, but by necyomancy, another type of divination, in which one uses a ring and a basin. See Necyomancy. See also Delrio, Disquisitionum Magicarum, Book IV, Chap. 2, Question VII, Section 3, pp. 564 and 565. [7]

1. Much of the French text matches the entry “Alectryomancie” in Chambers’s Cyclopaedia, though the French version contains additional details.

2. The original French text lists Pergamius as Bergamius. However, the article “Alectryomancie” in Panckoucke’s 1776 Supplément à l’Encyclopédie (1:262) includes this spelling correction, along with the following other corrections: 1) Marcellinus did not say that alectryomancy was used to find Valens’s successor, but rather dactylomancy; 2) Hilarius’s confession was reported by Ammianus Marcellinus, and not by Zonaras; 3) Divination using a ring and basin is dactylomancy, and not necyomancie or necromancy, which were practiced by evoking the dead.

3. Historian Ammianus Marcellinus (ca. 330-ca. 400) was known for his works on the history of Rome from 96-378 CE.

4. Zonaras (1074-1130) was a Byzantine historian.

5. Also spelled Iamblichus and Iamblicus.

6. Valens (328-378) was Roman emperor from 364-378.

7. Martin Delrio (1551-1608), a Jesuit theologian, authored classic commentaries as well as works on witchcraft and demonology. The work cited here, Disquisitionum magicarum (Magical Investigations) which appeared in three volumes in 1599 and 1600, is an example of the latter. A 1608 edition is available here.