Reposted from January 23, 2011
Blake uses the rainbow more as a visual image than a verbal image. Jerusalem appears here as a butterfly within the arc of a rainbow in the image at the bottom of Plate 14 of Jerusalem which shows Albion in his death-sleep. The heavenly bodies are portrayed in the plate as reminders of the universe measured in eons not minutes.
Jerusalem, Plate 13 & 14, (E 158)
"And all that has existed in the space of six thousand years:
Permanent, & not lost not lost nor vanishd, & every little act,
Word, work, & wish, that has existed, all remaining still
In those Churches ever consuming & ever building by the Spectres
Of all the inhabitants of Earth wailing to be Created:
Shadowy to those who dwell not in them, meer possibilities:
But to those who enter into them they seem the only substances
For every thing exists & not one sigh nor smile nor tear,
One hair nor particle of dust, not one can pass away.
He views the Cherub at the Tree of Life, also the Serpent,
Orc the first born coild in the south: the Dragon Urizen:
Tharmas the Vegetated Tongue even the Devouring Tongue:
A threefold region, a false brain: a false heart:
And false bowels: altogether composing the False Tongue,
Beneath Beulah: as a watry flame revolving every way
And as dark roots and stems: a Forest of affliction, growing
In seas of sorrow. Los also views the Four Females:
Ahania, and Enion, and Vala, and Enitharmon lovely.
And from them all the lovely beaming Daughters of Albion,
Ahania & Enion & Vala, are three evanescent shades:
Enitharmon is a vegetated mortal Wife of Los:
His Emanation, yet his Wife till the sleep of death is past.
Such are the Buildings of Los! & such are the Woofs of
The permanence and the multiplicity of the created world are described in the text. Blake has used words and images to remind us that there is an eternal world which underlies the vicissitudes of the temporal world. Because the image of the rainbow (which appeared after the Flood of Noah) is seen on this plate, Blake is going beyond the idea of an account of the physical body or the world of matter. The use of the rainbow makes the plate a token of a benevolent God's infinite care. We must remember that Blake uses water as a symbol for the material. To say that the world will not be destroyed by flood is to say the materiality shall not overcome spirituality.
When we seek out the biblical references for the rainbow we find this passage in Genesis 9:
 And I will establish my covenant with you; neither shall
all flesh be cut off any more by the waters of a flood; neither shall
there any more be a flood to destroy the earth.
 And God said, This is the token of the covenant which I make between me and you and every living creature that is with you, for perpetual generations:
 I do set my bow in the cloud, and it shall be for a token of a covenant between me and the earth.
 And it shall come to pass, when I bring a cloud over the earth, that the bow shall be seen in the cloud:
 And I will remember my covenant, which is between me and you and every living creature of all flesh; and the waters shall no more become a flood to destroy all flesh.
 And the bow shall be in the cloud; and I will look upon it, that I may remember the everlasting covenant between God and every living creature of all flesh that is upon the earth.
 And God said unto Noah, This is the token of the covenant, which I have established between me and all flesh that is upon the earth.
Genesis states that God covenants not to repeat the destruction of the earth and all living things by flood. The covenant is among God, man and the living creatures of the earth. The rainbow is a token of the covenant which is everlasting.
In Blake's 28 illustrations to Pilgrim's progress the rainbow colors appear frequently as reminders of the rainbow as a token. The rainbow image itself is prominent in three plates: the first, the last, and Plate 17. In Plate One the arc of the rainbow previews the pilgrim's journey as a reminder of God's providence as man travels through life. Christian at the Arbor shows the linkage between God and man, a reference to the incarnation through which physicality and spirituality become one. The rainbow above the arbor symbolizes that linkage. In the final picture, in which the fourfold ascension is portrayed, the pilgrims and angels are embedded in the rainbow becoming themselves tokens of the process of reaching the visionary goal.
Plate 1The Dreamer Dreams a Dream