a digression in order to describe what Satan observed
in the Sun after having landed there. The poet embraces an opportunity
for exercising his imaginative and descriptive powers by giving an ideal
description of what, judging from the appearance of the orb, might be
the natural condition of things existing on his surface--

There lands the Fiend, a spot like which perhaps
Astronomer in the Sun's lucent orb
Through his glazed optic tube, yet never saw.
The place he found beyond expression bright,
Compared with aught on Earth, metal or stone;
Not all parts like, but all alike informed
With radiant light, as glowing iron with fire;
If metal, part seemed gold, part silver clear;
If stone, carbuncle most or chrysolite,
Ruby or topaz, to the twelve that shone
In Aaron's breastplate, and a stone besides,
Imagined rather oft than elsewhere seen;
That stone, or like to that, which here below
Philosophers in vain so long have sought,
In vain, though by their powerful art they bind
Volatile Hermes, and call up unbound
In various shapes old Proteus from the sea,
Drained through a limbec to his native form.
What wonder then if fields and regions here
Breathe forth elixir pure, and rivers run
Potable gold, when, with one virtuous touch,
The arch-chemic Sun, so far from us remote,
Produces, with terrestrial humour mixed,
Here in the dark so many precious things
Of colour glorious, and effect so rare?
Here matter new to gaze the Devil met
Undazzled; far and wide his eye commands;
For sight no obstacle found here, nor shade,
But all sunshine, as when his beams at noon
Culminate from the equator, as they now
Shot upward still direct, whence no way round
Shadow from body opaque can fall; and the air,
Nowhere so clear sharpened his visual ray
To objects distant far, whereby he soon
Saw within here a glorious Angel stand.--iii. 588-622.

The physical structure of the interior of the Sun is unknown; all that
we see of the orb is the photosphere--the dazzling luminous envelope
which indicates to the eye the boundary of the solar disc, and which is
the source of light and heat. Milton, in his imaginative and beautifully
poetical description of the Sun, is not more fanciful in his conception
of the nature of the refulgent orb than a renowned astronomer (Sir
William Herschel) who writes in the fo