The remainder of the action required but three months more: for, when Æneas went for succour to the Tuscans, he found their army in a readiness to march, and wanting only a commander: so that, according to this calculation, the Æneïs takes not up above a year complete, and may be comprehended in less compass. This, amongst other circumstances treated more at large by Ségrais, agrees with the rising of Orion, which caused the tempest described in the beginning of the First Book. By some passages in the "Pastorals," but more particularly in the "Georgics," our poet is found to be an exact astronomer, according to the knowledge of that age. Now Ilioneus (whom Virgil twice employs in embassies, as the best speaker of the Trojans) attributes that tempest to Orion, in his speech to Dido: _Cum, subito assurgens fluctu, nimbosus Orion_-- He must mean either the heliacal, or achronical rising of that sign. The heliacal rising of a constellation is, when it comes from under the rays of the sun, and begins to appear before day-light; the achronical rising, on the contrary, is when it appears at the close of day, and in opposition to the sun's diurnal course. The heliacal rising of Orion is at present computed to be about the sixth of July; and about that time it is, that he either causes or presages tempests on the seas. Ségrais has observed farther, that, when Anna counsels Dido to stay Æneas during the winter, she speaks also of Orion-- _Dum pelago desævit hiems, et aquosus Orion._ If therefore Ilioneus, according to our supposition, understand the heliacal rising of Orion, Anna must mean the achronical, which the different epithets given to that constellation seem to manifest. Ilioneus calls him _nimbosus_; Anna, _aquosus_. He is tempestuous in the summer, when he rises heliacally, and rainy in the winter, when he rises achronically. Your lordship will pardon me for the frequent repetition of these cant words, which I could not avoid in this abbreviation of Ségrais, who, I think, deserves no little commendation in this new criticism.[68]