i.e., which had (would have) else swelled to the full, etc.

“This that I mixed with truth, motions of mine
That quickened, made the inertness malleolable
O’ the gold was not mine,”—
I. The Ring and the Book, v. 703.
“Harbouring in the centre of its sense
A hidden germ of failure, shy but sure,
Should neutralize that honesty and leave
That feel for truth at fault, as the way is too.”
I. The Ring and the Book, v. 851.
“Elaborate display of pipe and wheel
Framed to unchoak, pump up and pour apace
Truth in a flowery foam shall wash the world.”
I. The Ring and the Book, v. 1113.
“see in such
A star shall climb apace and culminate,”
III. The Other Half Rome, v. 846.
“Guido, by his folly, forced from them
The untoward avowal of the trick o’ the birth,
Would otherwise be safe and secret now.”
IV. Tertium Quid, v. 1599.
“so I
Lay, and let come the proper throe would thrill
Into the ecstasy and outthrob pain.”
VI. Giuseppe Caponsacchi, v. 972.
“blind?
Ay, as a man would be inside the sun,
Delirious with the plentitude of light
Should interfuse him to the finger-ends”—
X. The Pope, 1564.
“You have the sunrise now, joins truth to truth.”
X. The Pope, 1763.
“One makes fools look foolisher fifty-fold
By putting in their place the wise like you,
To take the full force of an argument
Would buffet their stolidity in vain.”
XI. Guido, 858.

Here the infinitive “To take” might be understood, at first look, as the subject of “Would buffet”; but it depends on “putting”, etc., and the subject relative “that” is suppressed: “an argument {that} would buffet their stolidity in vain.”

“Will you hear truth can do no harm nor good?”
XI. Guido, 1915.
“I who, with outlet for escape to heaven,
Would tarry if such flight allowed my foe
To raise his head, relieved of that firm foot
Had pinned him to the fiery pavement else!”
XI. Guido, 2099.

i.e., “that firm foot {that} had (would have) pinned.”

. . ."ponder, ere ye pass,
Each incident of this strange human play
Privily acted on a theatre,
Was deemed secure from every gaze but God’s,”—
XII. The Book and the Ring, v. 546.
“As ye become spectators of this scene—

—A soul made weak by its pathetic want
Of just the first apprenticeship to sin,
Would thenceforth make the sinning soul secure
From all foes save itself, that’s truliest foe,”—
XII. The Book and the Ring, v. 559.

i.e., “sin, {that} would.”

“Was he proud,—a true scion of the stock
Which bore the blazon, shall make bright my page”—
XII. The Book and the Ring, v. 821.

2. The use of the infinitive without the prepositive “to”, is frequently extended beyond present usage, especially in ‘Sordello’ and ‘The Ring and the Book’. The following are examples:—