Since, then, Scripture says that the dew or the rain falls from heaven, we understand that it is from those waters which have been ordered to occupy the higher regions.  When the exhalations from the earth, gathered together in the heights of the air, are condensed under the pressure of the wind, this aerial moisture diffuses itself in vaporous and light clouds; then mingling again, it forms drops which fall, dragged down by their own weight; and this is the origin of rain.  When water beaten by the violence of the wind, changes into foam, and passing through excessive cold quite freezes, it breaks the cloud, and falls as snow. cf. Arist., Meteor. i. 9–12, Plutarch περὶ τῶν ἀρέσκ. etc. iii. 4.  You can thus account for all the moist substances that the air suspends over our heads.