&6 ESSAYS anp OBSERVATIONS 
ferent altitude, may affume all the vari- 
ety of colours obferved in them at fun- 
rifing and fetting, by barely refleCting the 
fun’s incident light as they receive it? I 
have often obferved with pleafure, when 
in Switzerland, that the fnowy fummits 
of the Alps turn more and more reddifh 
after fun-fet, in the fame manner as the 
clouds. What makes the fame colours 
much more rick and copious in the clouds, 
is their fenmi-tranf{parency joined with the 
obpagaaty of their fituation, 
Doss it not greatly confirm this expli- 
cation, that thefe coloured clouds imme- 
diately, refume that dark leaden hue which 
they receive from the fky as foon as the 
fun’s direct rays ceafe to ftrike upon 
them? For, if their gaudy colours arofe, 
like thofe of the foap-bubble, from the 
particular fize of their parts, they would 
pre(erve nearly the fame colours, though 
much fainter, when illuminated only by 
the atmofphere. About the time of fun- _ 
fet, or a little after, the lower part of the 
ikky, to fome diftance on each fide from 
the place of his fetting, feems to incling 
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