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On the Nature of Things

Titus Lucretius Carus · c. 60–55 BCE (books composed over this period) primary

passage 128 of 143 · BOOK I > BOOK VI (11/26)

in brief
Lucretius describes cloud formation from interlinked airborne particles: mists rise with upward winds and evaporation from sea, rivers, and shores, condense into small clouds, merge into larger thunderheads, and the atmosphere provides “exits and entrances” for particles.

most but rarely, and on land the hills Must block its way, 'tis seen more oft out there On the broad prospect of the level main Along the free horizons.

Into being The clouds condense, when in this upper space Of the high heaven have gathered suddenly, As round they flew, unnumbered particles-- World's rougher ones, which can, though interlinked With scanty couplings, yet be fastened firm, The one on other caught. These particles First cause small clouds to form; and, thereupon, These catch the one on other and swarm in a flock And grow by their conjoining, and by winds Are borne along, along, until collects The tempest fury. Happens, too, the nearer The mountain summits neighbour to the sky, The more unceasingly their far crags smoke With the thick darkness of swart cloud, because When first the mists do form, ere ever the eyes Can there behold them (tenuous as they be), The carrier-winds will drive them up and on Unto the topmost summits of the mountain; And then at last it happens, when they be In vaster throng upgathered, that they can By this very condensation lie revealed, And that at same time they are seen to surge From very vertex of the mountain up Into far ether. For very fact and feeling, As we up-climb high mountains, proveth clear That windy are those upward regions free. Besides, the clothes hung-out along the shore, When in they take the clinging moisture, prove That nature lifts from over all the sea Unnumbered particles. Whereby the more 'Tis manifest that many particles Even from the salt upheavings of the main Can rise together to augment the bulk Of massed clouds. For moistures in these twain Are near akin. Besides, from out all rivers, As well as from the land itself, we see Up-rising mists and steam, which like a breath Are forced out from them and borne aloft, To curtain heaven with their murk, and make, By slow foregathering, the skiey clouds. For, in addition, lo, the heat on high Of constellated ether burdens down Upon them, and by sort of condensation Weaveth beneath the azure firmament The reek of darkling cloud. It happens, too, That hither to the skies from the Beyond Do come those particles which make the clouds And flying thunderheads. For I have taught That this their number is innumerable And infinite the sum of the Abyss, And I have shown with what stupendous speed Those bodies fly and how they're wont to pass Amain through incommunicable space. Therefore, 'tis not exceeding strange, if oft In little time tempest and darkness cover With bulking thunderheads hanging on high The oceans and the lands, since everywhere Through all the narrow tubes of yonder ether, Yea, so to speak, through all the breathing-holes Of the great upper-world encompassing, There be for the primordial elements Exits and entrances.

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topics: experiment, observation, and evidence · matter, motion, and cause · the earth and its formation · weather, storms, and the seasons

On the Nature of Things · Titus Lucretius Carus · 60–55 BCE