THE SUN AND SOLAR PHENOMENA. 
301 
the other bodies of the system. Imagine a degree of heat some 
three hundred thousand times greater than that which exists on 
the earth., and which would turn our purest metals into fumes. 
No end of wild conjectures or grand conceptions can be made 
in connection with the scenery of this new world. 
What wonder, then, if fields and regions here 
Breathe forth elixir pure, and rivers run 
Potable gold, when with one virtuous touch 
Th’ arch-chemic sun, from us so far remote, 
Produces, with terrestrial humour mixed, 
Here in the dark so many precious things 
Of colours glorious and effects so rare. 
It must not be forgotten, however, that the principal error 
of those who start theories on the light and heat of the sun, — 
who would reduce those elements to material fuel and agency, 
— has been in their supposition that the sun and planets — the 
donor and the recipients — are bodies of a similar nature, and 
that the same conditions are general throughout the system, 
whether it be star or planet, satellite or comet. 
Those who have looked at the sun with a telescope of even 
moderate power, have of course observed the dark spots on its 
disc. They have seen them of eveiy conceivable size and form, 
and it very seldom happens that they have any appearance 
of regularity further than that they are commonly approxi- 
mately circular. These spots are surrounded by a lighter 
shade, which is mostly of the same form as the central speck, 
and which seems like a fringe of less-dense material, parting 
abruptly from the more obscure kernel which it incloses. 
This intermediate shade does not mix with the densely black 
nucleus, at the same time it is distinctly separate from the 
illuminated surface of the sun. This is most strictly true in 
every instance : the nucleus or spot proper is of one tint, and 
that a very intense black ; the penumbra, or fringe, of an 
equally constant though much milder degree of shade — a sort of 
half-mourning; whilst the brilliant lustre of the solar surface 
makes a third tint. There are thus three distinct and sharply- 
defined grades, and these facts must be strictly borne in mind by 
all those who would endeavour to explain the physical constitution, 
of the sun. Sir W. Herschel accounted for it in this manner : 
The outer luminous surface which it blinds us to look at he 
considered is composed of a fiery and cloudy matter supported 
by a transparent medium similar to our atmosphere. When 
the bright envelope, either from volcanic disturbance or other 
agitation within, or from currents from without, is broken, we 
perceive the upper portion of the inner atmosphere illuminated 
by the light which it receives from above, and at the same 
