SECT, xviii.] ATMOSPHERIC ABSOEPTION. 177 



great a quantity of light is lost in passing through the 

 atmosphere, many celestial objects may be altogether in- 

 visible from the plain, which may be seen from elevated 

 situations. Diminished splendour, and the false estimate 

 we make of distance from the number of intervening ob- 

 jects, lead us to suppose the sun and moon to be much 

 larger when in the horizon than at any other altitude, 

 though their apparent diameters are then somewhat less. 

 Instead of the sudden transitions of light and darkness, 

 the reflective power of the air adorns nature with the rosy 

 and golden hues of the Aurora and twilight. Even when 

 the sun is eighteen degrees below the horizon, a sufficient 

 portion of light remains to show, that at the height of 

 thirty miles it is still dense enough to reflect light. The 

 atmosphere scatters the sun's rays, and gives all the beau- 

 tiful tints and cheerfulness of day. It transmits the blue 

 light in greatest abundance; the higher we ascend, the 

 sky assumes a deeper hue; but, in the expanse of space, 

 the sun and stars must appear like brilliant specks in pro- 

 found blackness 



