That the generation of rains comes from the evaporation of the humid, he demonstrates, saying (I. xi. 54):—
Who sent from Heav'n a show'r of blood-stained rain,—
and (I. xvi. 459):—
But to the ground some drops of blood let fall,—
for he had previously said (I. vii. 329):—
Whose blood, beside Scamander's flowing stream,
Fierce Mars has shed, while to the viewless shade
Their spirits are gone,—
where it is evident that humors of this sort exhaled from the waters about the earth, mixed with blood, are borne upward. The same argument is found in the following (I. xvi. 385):—
As in the autumnal season when the earth with weight of rain is saturate,—for then the sun on account of the dryness of the ground draws out humors from below and brings from above terrestrial disturbances. The humid exhalations produce rains, the dry ones, winds. When the wind is in impact with a cloud and by its force rends the cloud, it generates thunder and lightning. If the lightning falls, it sends a thunderbolt. Knowing this our poet speaks as follows (I. xvii. 595):—
His lightnings flash, his rolling thunders roar.
And in another place (O. xii. 415):—