Taking Valanus, in the first place, as a proper name, the most probable original would be Valens; for the connexion of which with Mercury we must refer to Cicero (De Nat. Deor. iii. 22.), where mention is made of it in these words:—
"Alter (Mercurius) Valentis et Phoronidis filius, is qui sub terris habetur idem Trophonius."
Here the identification with Trophonius strikes us at once as affording a clue to THE CAVE into which Venus fled, giving great probability to Valens as the true solution of Chaucer's meaning.
But if we receive it as such, the following hypothesis becomes necessary, viz., that Chaucer imagined a double impersonation of Mercury—one absent, the other present,—one sidereal, the other mythological,—one Cyllenius, the other Valens.
When Venus first enters Mercury's "palais," she "ne found ne sey no maner wight." This signifies the absence from home of Cyllenius, who was abroad upon "his chirachee" in attendance upon the Sun; and here again is an instance of the nice astronomical accuracy of Chaucer. It was impossible that the planet Mercury could be in the sign Gemini, because his greatest elongation, or apparent distance from the sun, does not exceed 29 degrees; so that the Sun having but just entered Taurus, Mercury could not be in Gemini. Neither could Venus see Valens (the other impersonation of Mercury), because of his concealment in the cave; but when she entered the cave, then she was welcomed and received by him.
Now, to render the text conformable with this interpretation, some alteration in the construction is necessary, as indeed it must be in any attempt to render the passage intelligible.
Taking, away the word "Fro," and transposing "might" to the other side of "Valanus," the lines would stand thus,—
"—— it happed for to be
That, while the weping Venus made her mone,
(Cyllenius riding in his chirachee)