Zl6 OF THE MOTION, REFRACTION,

and full bason : and if a stick be laid across thebason, and the sun’s rays be reflected perpendi-cularly into it from a looking-glass, the shadowof the stick will fall upon the same part of thebottom, whether the bason be full or empty.The same effects will also t^ke place when theexperiment is performed with any other fluid:but the denser the medium, the more will lightbe refracted in pasting through it.

From these observations it will readily appear,that objects can seldom be seen in their trueplaces. We are deceived by every thing aroundus : the fight is no less subject to error than therest of our senses: they all contribute to ourpleasure, and promote our happiness by variousmeans. In consequence of this property of re-fraction, we enjoy the light of the fun whilsthe is yet below the horizon; this being thecause that produces the crepusculum, or themorning and evening twilight. The sun’s rays,in falling upon the higher part of the atmo-sphere, are reflected back to our eyes, and forma faint light, which gradually augments till itbecomes day. It is in those brilliant coloursthat paint the clouds, before the rising of thefun, that the poets have placed Aurora, or thegoddess of the morn : she opens the gates ofday with her rosy fingers; and the daughterof the air and the sun has her throne in theatmosphere.

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