What figure of speech is "trèfles de braise" in "The Hunchback of Notre-Dame"?

Question

This is an extract of Book X, chapter IV of Victor Hugo's novel Notre-Dame de Paris (The Hunchback of Notre-Dame, emphasis mine):

Tous les yeux s'étaient levés vers le haut de l'église. Ce qu'ils voyaient était extraordinaire. Sur le sommet de la galerie la plus élevée, plus haut que la rosace centrale, il y avait une grande flamme qui montait entre les deux clochers avec des tourbillons d'étincelles, une grande flamme désordonnée et furieuse dont le vent emportait par moments un lambeau dans la fumée. Au-dessous de cette flamme, au-dessous de la sombre balustrade à trèfles de braise, deux gouttières en gueules de monstres vomissaient sans relâche cette pluie ardente qui détachait son ruissellement argenté sur les ténèbres de la façade inférieure.

Here you can read a translation of this extract (translated by Isabel F. Hapsgood):

All eyes were raised to the top of the church. They beheld there an extraordinary sight. On the crest of the highest gallery, higher than the central rose window, there was a great flame rising between the two towers with whirlwinds of sparks, a vast, disordered, and furious flame, a tongue of which was borne into the smoke by the wind, from time to time. Below that fire, below the gloomy balustrade with its trefoils showing darkly against its glare, two spouts with monster throats were vomiting forth unceasingly that burning rain, whose silvery stream stood out against the shadows of the lower façade.

My question is about the expression "trèfles de braise", which can be translated as "trefoils of embers". Which figure of speech is that?

Answer 1

The figure of speech is a metaphor.

One definition of metaphor is:

A figure of speech in which a word or phrase is applied to an object or action to which it is not literally applicable.

Since what Hugo is describing are not literally trefoils of embers, this is encompassed by this (rather broad) definition of metaphor. I don't know of any other, more specific, figures of speech which would include this phrase.

The balustrade is decorated with trefoils. Over a hundred pages earlier, we have:

En ce moment, Bérangère de Champchevrier, svelte petite fille de sept ans, qui regardait dans la place par les trèfles du balcon, s'écria:

Which in Isabel F. Hapgood's translation is:

At that moment, Bérangère de Champchevrier, a slender little maid of seven years, who was peering into the square through the trefoils of the balcony, exclaimed,

So the trèfles are cut out from the balcony. And through the trefoils cut out of the darker balustrade, you can see flames or sparks. So instead of saying that you can see flames through the cut-out trefoils, Hugo just calls them trefoils of embers.

Here (from Wikipedia) is a picture of a balustrade of Notre Dame, with trefoils.

Answer 2

Perhaps the phrase can be regarded as a transferred epithet or hypallage. Hypallage is a figure of speech wherein a descriptor (epithet) appropriate to a certain noun is applied (transferred) to a different noun. Transferred epithets are so common in everyday use, we no longer notice them. An example is the term waiting room. The room itself doesn't wait; the people inside it do. So the epithet waiting has been transferred to the room.

Another example can be found in the sentence, "She took comfort in her memories of happier times." It's not the times that were happier. She was happier during those times. Again, the epithet happier is transferred from the person to the times.

Generally transferred epithets are adjectives, but descriptive phrases can also be considered transferred epithets. Take the sentence, "Upon hearing the news, I wept tears of joy." Can of joy be considered a transferred epithet? Why not? Consider a change in phrasing: "I wept joyful tears." Here, there's no question that joyful has been transferred from the first person subject to the tears. The same argument pertains for of joy, which we can therefore confidently regard as a transferred epithet.

In the phrase trèfles de braise, the trefoils aren't of embers. They're empty space, and as such, they're not of anything. Like the tears, times, or room in the previous examples, the trefoils themselves cannot justify the term applied to them. The embers, were are any, would belong to the fire. But since the fire is visible through the trefoils, they appear to be the embers from which the flames arise. So the embers are metaphorically transferred to the trefoils.