Note to Julius Caesar, Act 2, Scene 1, line 44, "exhalations"
Brutus refers to a meteor shower as "exhalations" because the people of Shakespeare's time generally accepted Aristotle's explanation of meteors. Aristotle (in Meteorology, 350 B.C.) said that moist exhalations, such as mist and fog, rise from the earth and return as rain, sleet, and snow. This is what we think today, but Aristotle also wrote that the earth gives off dry exhalations, which rise into the upper atmosphere where they are lighted into fire (either by the speed of their motion or by being condensed by the surrounding cold) and return to earth as meteors.
