Institutio Oratoria

Similarly it is also usual to give the names of signs to frequently observed phenomena, such as prognostics of the weather which we may illustrate by the Vergilian

1. For wind turns Phoebe's face to ruddy gold

Verg. G. i. 431.

and

1. The crow
2. With full voice, good-for-naught, invites the rain.

ib. i. 388.

If these phenomena are caused by the state of the atmosphere, such an appellation is correct enough.

For if tile moon turns red owing to the wind, her hue is certainly a sign of wind. And if, as the same poet infers, [*]( Verg. G. i. 422. ) the condensation and rarification of the atmosphere causes that

concert of bird-voices

of which he speaks, we may agree in regarding it as a sign. We may further note that great things are sometimes indicated by trivial signs, witness the Vergilian crow; that trivial events should be indicated by signs of greater importance is of course no matter for wonder.