From Chapter 22 of The Princess and the Goblin by MacDonald:
And from somewhere came the voice of the lady, singing a strange sweet song, of which she could distinguish every word; but of the sense she had only a feeling--no understanding. Nor could she remember a single line after it was gone. It vanished, like the poetry in a dream, as fast as it came. In after years, however, she would sometimes fancy that snatches of melody suddenly rising in her brain must be little phrases and fragments of the air of that song; and the very fancy would make her happier, and abler to do her duty.
From Chapter 10 of The Voyage of the Dawn Treader by Lewis:
On the next page she came to a spell "for the refreshment of the spirit." The pictures were fewer here but very beautiful. And what Lucy found herself reading was more like a story than a spell. It went on for three pages and before she had read to the bottom of the page she had forgotten that she was reading at all. She was living in the story as if it were real, and all the pictures were real too. When she had got to the third page and come to the end, she said, "That is the loveliest story I've ever read or ever shall read in my whole life. Oh, I wish I could have gone on reading it for ten years. At least I'll read it over again."
But here part of the magic of the Book came into play. You couldn't turn back. The right-hand pages, the ones ahead, could be turned; the left-hand pages could not.
"Oh, what a shame!" said Lucy. "I did so want to read it again. Well, at least I must remember it. Let's see . . . it was about . . . about . . . oh dear, it's all fading away again. And even this last page is going blank. This is a very queer book. How can I have forgotten? It was about a cup and a sword and a tree and a green hill, I know that much. But I can't remember and what shall I do?"
And she never could remember; and ever since that day what Lucy means by a good story is a story which reminds her of the forgotten story in the Magician's Book.
And from Chapter 16 of The Voyage of the Dawn Treader by Lewis:
And suddenly there came a breeze from the east, tossing the top of the wave into foamy shapes and ruffling the smooth water all round them. It lasted only a second or so but what it brought them in that second none of those three children will ever forget. It brought both a smell and a sound, a musical sound. Edmund and Eustace would never talk about it afterward. Lucy would only say, "It would break your heart." "Why," said I, "was it so sad?" "Sad!! No," said Lucy.
I may not have noticed the connection between these passages if the above Narnia quotes weren't some of my favorite passages in the series. In all three instances, there is a message or moment that is valued but not quite comprehended. It has come and gone, yet, while remembered however vaguely, is a formative moment. Irene's moment is ever valued as encouragement, and when Lewis pays homage the appreciation has deepened to a longing. Longing for those fleeting moments of eternity in the now. Longing for peace, calm, wholeness, completeness. Longing for heaven. In MacDonald, the rest of heaven encourages and enables completion of labor required on earth. In Lewis, the weariness of earth creates a longing for the rest of heaven. Lewis understood this moment of not-quite-comprehended eternity in MacDonald, and the echoes are heard in Narnia.
If Lucy and Irene were to meet, they would surely be friends and would understand each other, even when what is understood is, paradoxically, inexpressible and beyond comprehension.