^8 On the Phenbmtha, of the Morning and Evening Dew. 



that there (hbiild be on all fides a lateral divergence, which muft evidently take place where 

 the preiTure is leaft. Thus on the fanle fuppofition of the earth being a plane, we thould 

 obferve the upper air defcend and precipitate itfelf along the fides of the cone, producing 

 by this oblique direction to the axis, a current on all fides directed from the fun ; and thts 

 curtetlt would be incrcafed by the vacuum formed at thofe places where the air is fuffi- 

 ciently elevated, and could precipitate its fupetabhndant water. 



This image will require very little more dificaticn to apply it to the exterior of our globe. 

 The conical furface will be converted into a cap, enveloping thejenlightencd portion of the 

 earth, and following the curvature produced by the currents. 



Infpedlion alone of the 6gure in Plate 3, will (hew this curvature. The globe may be 

 readily feen placed in the center of a circular ftratum, fuppofed to be filled by the atmof- 

 phere. The circumference of the earth has twenty-four divifions, from which are raifed a 

 like number of perpendiculars to its furface, or vertical lines, in order to afford a notion of 

 the change of phenomena from hour to hour. The fun fuppofed to be placed at S, in'the 

 in the continuation of the line TS, is fuppofed to have all its mafs united in the center; 

 and laflly, the curve a-, b, c, though arbitrarily drawn, becaufe its law is unknown, will be 

 fufficient to fhew the exiftence of the efFe£ts which we are interefted to explain. 



Such, therefore, will bs the refult of the fuppofed circumftances. Water diffolved by 

 the lower air expofed to the fun ; a motion of afcent in this part ; defcending divergent 

 currents on all fides, fpreading over the earth. Thefe currentrs, moreover, communicate 

 their Water to the heated columns, which rife and diverge laterally ; and this water is pre- 

 cipitated, becaufe the air of the currents proceeding from the upper regions is too cold 

 to keep it in folution, or becaufe the preflure is lefs from the diminithed weight of the 

 columns, as their diftance from the line immediately beneath the fun is greater, as well as 

 becaufe they may mix with other cold air near the furface ; an4 laflly, the ground, and all 

 other bodies in the direction of this precipitated water, will be wetted therewith. 



The morning and evening dews are here evident to our confideration, with the wind 

 and the cold which attend them ; but a few more remarks are wanting to complete the 

 defcription. We muft firft obferve that the defcending currents are prolonged till the 

 refiftance of the air, through which they pafs, has entirely deftroyed their motion. Again, 

 we fhall fee immediately beneath the fun, a circular fpace greatly heated, which does not 

 prefent to the inhabitants of that region the phenomenon we have been defcribing. As 

 we depart from this fpace, and in proportion as the fun appears in a more oblique direc- 

 tion, we arrive at a region lefs heated, where the wind from the diredtion of the fun, and 

 the precipitation of moillure, begins to be perceived. This region forms a crown round 

 the circular fpace before mentioned. And, laftly, by departing ftill more from the inner 

 border of this crown, the wind is found to be ftronger, the cold more perceptible, and the 

 ptecipitation of water more abundant ; which effefts afterwards diminifh to a certain 

 diftance, and entirely ceafe at the furface of the earth diametrically oppofite the fun. 



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