(1) _Dirae._—These were a heterogeneous collection of signs of ill omen. Anything that broke the silence (_silentium_)[676] when the auspices were being taken was of this character, such as the fall of anything in a temple (_caducum auspicium_),[677] or a sudden noise, such as the squeak of a mouse.[678] Such too was any sudden event that seemed to warn back from a course once taken—the flight of ravens towards the walker or round his head, and the stumbling of his foot on the threshold;[679] the struggle of birds in the air ending in the defeat of those that had flown from the direction of the general’s camp;[680] the seizing of the boundary stones of a newly laid-out city by wolves,[681] and countless others. A peculiarly dreadful omen was a fit of epilepsy, called, from its power of suspending the assemblies, _morbus comitialis_. Such signs, to be effective hindrances, must have an obvious connexion in time and place with the act they impede, and must, besides, be noticed by the agent. Hence a flash of lightning was the most effective of _auspicia oblativa_. Less potent signs could be ignored by veiling the senses. The augur, who is asked by the officiating magistrate if there is silence, does not look round him, but straightway answers “yes”;[682] in sacrifice flutes are blown to drown all other sounds,[683] and the general bent on fighting takes the precaution of travelling in a closed litter.[684] If another person forced the omen on the magistrate’s notice, he was bound to attend to it. This announcement (_nuntiatio_ or _obnuntiatio_) we shall speak of elsewhere; it belongs to the history of the conflict between the authorities of the different magistrates. The four other classes of omens belong to the category of _auspicia impetrativa_. These were— (2) Signs from the flight of birds (_signa ex avibus_), the oldest form of augural discipline, as the very words _augures_ and _auspicium_ prove, and one that in the early Republic was used in all solemn acts of state, such as the summons of the _comitia_ or the appointment of a dictator.[685] (3) Closely akin to this was the augury from the motions and sounds of four-footed beasts (_signa ex quadrupedibus_); but by the close of the Republic these forms of divination, which required study and research, had given place to the two remaining classes, which were more easily interpreted, or more readily manipulated for political purposes. These were the _coelestia auspicia_ and the _auspicia ex tripudiis_.[686] (4) Chief of the heavenly signs (_celestia auspicia_), and the surest expression of Jupiter’s will, were thunder and lightning. Thunder seems sometimes to have been regarded as a wholly evil omen;[687] but the course taken by the lightning determined its significance—if on the watcher’s left, it was lucky; if on the right, unlucky.[688]