lire in them when blown 1>\ a u in. I. m- to tin- rending and disruption of clouds, or to the friction and splitting up of clouds when they have become as linn as ice. As in the whole survey, so in this particular point, the facts invite us to give a plurality of explanations. Lightnings too happen in a variety of ways. For when '"the clouds rub against each other and collide, that collocation of atoms which is the cause of lire generates lightning ; or it may be due to the flashing forth from the clouds, by reason of winds, of particles capable of producing this brightness ; or else it is squeezed out of the clouds when they have been condensed either by their own action or by that of the winds ; or again, the light diffused from the stars may be enclosed in the clouds, then driven about by their motion and by that of the winds, and finally make its escape from the clouds ; or light of the finest texture may be filtered through the clouds (whereby the clouds may be set on fire and thunder produced), and the motion of this light may make lightning ; or it may arise from the combustion of wind brought about by the violence of its motion and the intensity of its compression ; or, when the clouds are rent asunder by winds, and the atoms which generate fire are expelled, these likewise cause lightning to appear. And it may easily be seen that its occurrence is possible in many other ways, so long as we hold fast to facts and take a general view of what is analogous to themj | Lightnmgprecedes thunder, when the clouds are constituted as mentioned above and the configuration which produces lightning is expelled at the moment when the wind falls upon the cloud, and Of Lncr. vi. 271-284.