Louis le Débonnaire gave himself and his court to fasting and prayer, and built churches and monasteries. He died three years later, in 840, and historians have profited by this slight coincidence to prove that the appearance of the comet was a harbinger of death. The historian, Raoul Glader, added later: "These phenomena of the universe are never presented to man without surely announcing some wonderful and terrible event." Halley's comet again appeared in April, 1066, at the moment when William the Conqueror invaded England. It was pretended that it had the greatest influence on the fate of the battle of Hastings, which delivered over the country to the Normans. A contemporary poet, alluding probably to the English diadem with which William was crowned, had proclaimed in one place, "that the comet had been more favorable to William than nature had been to Caesar; the latter had no hair, but William had received some from the comet." A monk of Malmesbury apostrophized the comet in these terms: "Here thou art again, thou cause of the tears of many mothers! It is long since I have seen thee, but I see thee now, more terrible than ever; thou threatenest my country with complete ruin!" In 1455, the same comet made a more memorable appearance still. The Turks and Christians were at war, the West and the East seemed armed from head to foot--on the point of annihilating each other. The crusade undertaken by Pope Calixtus III. against the invading Saracens, was waged with redoubled ardor on the sudden appearance of the star with the flaming tail. Mahomet II. took Constantinople by storm, and raised the siege of Belgrade. But the Pope having put aside both the curse of the comet, and the abominable designs of the Mussulmans, the Christians gained the battle, and vanquished their enemies in a bloody fight. The _Angelus_ to the sound of bells dates from these ordinances of Calixtus III. referring to the comet. In his poem on astronomy, Daru, of the French Academy, describes this episode in eloquent terms: "Un autre Mahomet a-t-il d'un bras puissant Aux murs de Constantine arboré le croissant: Le Danube étonné se trouble au bruit des armes, La Grèce est dans les fers, l'Europe est en alarmes; Et pour comble d'horreur, l'astre au visage ardent De ses ailes de feu va couvrir l'Occident. Au pied de ses autels, qu'il ne saurait défendre, Calixte, l'oeil en pleurs, le front convert de cendre, Conjure la comète, objet de tant d'effroi: Regarde vers les cieux, pontife, et lève-toi! L'astre poursuit sa course, et le fer d'Huniade Arrête le vainqueur, qui tombe sous Belgrade. Dans les cieux cependant le globe suspendu, Par la loi générale à jamais retenu, Ignore les terreurs, l'existence de Rome, Et la Terre peut-être, et jusqu'au nom de l'homme, De l'homme, être crédule, atome ambitieux, Qui tremble sous un prêtre et qui lit dans les cieux."