Dr. Herschel’s Observations to investigate 
3 ° 4 « 
Formation of Corrugations. 
When this empyreal gas has reached the higher regions of 
the sun's atmosphere, it mixes with other gases, which, from 
their specific gravity, have their residence there, and occasions 
decompositions which produce the appearance of corrugations. 
It has been shewn, that the elevated parts of the corrugations are 
small self-luminous nodules, or broken ridges ; and I have used 
the name of self-luminous clouds, as a general expression for all 
phenomena of the sun, in what shape soever they may appear, 
that shine by their own light. These terms do not exactly con- 
vey the idea affixed to them ; but those of meteors, corusca- 
tions, inflammations, luminous wisps, or others, which I might 
have selected, would have been liable to still greater objections. 
It is true, that when speaking of clouds, we generally conceive 
something too gross, and even too permanent, to permit us to 
apply that expression properly to luminous decompositions, 
which cannot float or swim in air, as we are used to see our 
planetary clouds do. But it should be remembered, that, on 
account of the great compression arising from the force of 
gravity, all the elastic solar gases must be much condensed ; 
and that, consequently, phenomena in the sun's atmosphere, 
which in ours would be mere transitory coruscations, such as 
those of the aurora borealis, will be so compressed as to become 
much more efficacious and permanent. 
Cause of Indentations. 
The great light occasioned by the brilliant superior regions, 
must scatter itself on the tops of the inferior planetary clouds, 
and, on account of their great density, bring on a very vivid re- 
flection. Between the interstices of the elevated parts of the 
