"On the 25th of March, 1742, West had asked Gray's opinion of the 4th Book of the Dunciad which had just appeared ("the New Dunciad: Qu'en pensez-vous?"). Gray between this date and April sent West a brief criticism of it. It was fresh in his mind when he wrote this fragment, obviously inspired by Pope; the new Dunciad gave him also in part the expression "the silken son of dalliance" in Agrippina, which he had in hand at the date of the above letters. In July 1742 in a letter hitherto assigned to 1745), he wrote to Chute, "I am just going into the country for one easy fortnight, and then in earnest intend to go to Cambridge, to Trinity Hall"—(he in fact returned to Peterhouse, I believe as a fellow-commoner).
Gray had left Cambridge in September 1738. From the lines

''Thrice hath Hyperion roll'd his annual race,
Since weeping I forsook thy fond embrace,''

we may safely conclude that this 'Hymn' was written before September 1742. It is probable that it was written much earlier in that year; and the lines just quoted perhaps indicate that Gray had reluctantly made up his mind to return to Cambridge, even before the death of West. This Hymn forms a prelude—though a very sinister prelude—to his long residence at Cambridge, and the poems he there composed, and this seems the best place for it.
Perhaps also this may be the best place to point out a singular parallel between moments in the life-story of Milton and of Gray. If we combine this Hymn to Ignorance with the letters which Gray between his return from the Continent and his return to Cambridge wrote to West and Chute, we have a picture which corresponds detail for detail with the account which Milton gives in the first of his Latin elegies of his feeling towards Cambridge, and the way in which he spent his time during his supposed rustication from the University, to which like Gray he professes himself reluctant to go back, though he forces himself to do it:

''Stat quoque juncosas Cami remeare paludes
  Atque iterum raucae murmur adire Scholae.''
            Eleg. I. 89, 90.
''And I will e'en repass Cam's reedy pools
To face once more the warfare of the Schools.'' (Cowper.)

It was to his father's house in London that Gray went when he came from abroad; and probably from the same house that his letters from town of this period were written, though his father died about two months after his return. Milton's father was a money-scrivener; so was Gray's; London was the native city of both poets. Milton writes (Eleg. I. 9, 10)

''Me tenet urbs refluâ quam Thamesis alluit undâ
  Meque, nec invitum, patria dulcis habet,''

and implies that it was no banishment ''patrios adiisse penates'' (l. 17). Cambridge and its surroundings are uncongenial to a lover of the Muses:

''Nuda nec arva placent, umbrasque negantia molles:
  Quam male Phoebicolis convenit ille locus!''
''Nor aught of pleasure in those fields have I,
That to the musing bard all shade deny.'' (Cowper.)

His life he says is pleasantly spent between his books, the public parks and gardens and the theatre (compare Gray's later letters to West and those to Chute of Sept. 7, 1741, and July 1742). The friendship between Milton and Charles Diodati, to whom this Elegia is written, has its exact counterpart in that between Gray and West. Milton and Diodati were schoolfellows at S. Paul's, as Gray and West were schoolfellows at Eton. In both instances the friends were separated by a different choice of University; Milton and Gray went to Cambridge: Diodati and West to Oxford. Both pairs of friends corresponded in much the same fashion; in particular they cheered and advised each other with much solicitude; the Elegia I. of Milton is called forth by a letter from Diodati, rebuking him for poring too much over his books, which exactly resembles extant letters from Gray to West, and West to Gray. The parallel extends yet further. Both Diodati and West died prematurely; Diodati while Milton was upon his foreign travels; West, not very long after Gray had returned from his. Diodati's death is the subject of the most beautiful of Milton's Latin poems, the Epitaphium Damonis; West's, of the sonnet we have annotated, and of the beautiful tribute which closes all that Gray has written of his ''De Principiis Cogitandi.'' "

Gray's English Poems, Original and Translated from the Norse and Welsh. Edited by Duncan C. Tovey. Cambridge: Cambridge UP, 1922 [1st ed. 1898], p. 102-103.