With its own matter; or, as bodies share
Their fat and leanness, in like manner this
Must in its volume change the leaves. The first,
If it were true, had through the sun's eclipse
Been manifested, by transparency
Of light, as through aught rare beside effus'd.
But this is not. Therefore remains to see
The other cause: and if the other fall,
Erroneous so must prove what seem'd to thee.
If not from side to side this rarity
Pass through, there needs must be a limit, whence
Its contrary no further lets it pass.
And hence the beam, that from without proceeds,
Must be pour'd back, as colour comes, through glass
Reflected, which behind it lead conceals.
Now wilt thou say, that there of murkier hue
Than in the other part the ray is shown,
By being thence refracted farther back.
From this perplexity will free thee soon
Experience, if thereof thou trial make,
The fountain whence your arts derive their streame.
Three mirrors shalt thou take, and two remove
From thee alike, and more remote the third.
Betwixt the former pair, shall meet thine eyes;
Then turn'd toward them, cause behind thy back
A light to stand, that on the three shall shine,
And thus reflected come to thee from all.
Though that beheld most distant do not stretch
A space so ample, yet in brightness thou
Will own it equaling the rest. But now,