Could you please tell me if "scales" in the following excerpt from Chapter Three of The Great Gatsby by F. Scott Fitzgerald means 1) "an instrument for weighing" (with an allusion to the Libra), 2) "any of the thin plates of hard material that cover the skin of many fish and reptiles", or something else?
The moon had risen higher, and floating in the Sound was a triangle of silver scales, trembling a little to the stiff, tinny drip of the banjoes on the lawn.
The moonlight shining on slightly choppy water could be said to resemble the scales on fish or the metal scales on some kinds of flexible armor. The scales might be said to be "trembling" to the banjo music, but actually they would be trembling to the rippling of the ocean water. They would appear to have the shape of a triangle if the moonlight was expanding on the water from the horizon towards the observer, with the moon as a single point in the distance. This effect of light on water is common even in swimming pools if the water is the least bit unstable.
Fitzgerald borrowed the phrase "Tender is the night" from Keats' "Ode to a Nightingale" for the title of his novel Tender is the Night. Fitzgerald must have been fond of Keats. His prose often reminds me of Keats' poetry in its rather daring and generous use of similes and metaphors, especially metaphors. I guess I am also reminded of Shakespeare's sonnets. For example:
That time of year thou mayst in me behold
When yellow leaves, or none, or few do hang
Upon those boughs which shake against the cold,
Bare ruin'd choirs, where late the sweet birds sang.
The boughs do not shake because they are cold but because they are being agitated by the wind; but they seem to be trembling from the cold, which suggests further that they are conscious beings with physical sensations. Neither are the scales on the water in The Great Gatsby trembling because they can hear the banjo music and presumably enjoying it, even possibly dancing to it; they are trembling because the water is trembling, and the water is trembling because there is a little breeze. Fitzgerald can take such impressionistic poetic liberties in his descriptions. Aristotle said that the ability to create striking metaphors and similes is an infallible sign of genius. Of course, Keats was heavily influenced by Shakespeare, as were most English poets.