“Everything that is dead quivers. Not only the things of poetry, stars, moon, wood, flowers, but even a white trouser button glittering out of a puddle in the street… Everything has a secret soul, which is silent more often than it speaks.”

Lecture, "Seemliness" (Glasgow, 1902), as cited in: David Brett, C. R. Mackintosh: The Poetics of Workmanship, (2004), p. 56

Quoted by Plutarch, De gloria Atheniensium 3.346f http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A2008.01.0234%3Astephpage%3D346f.
Variant translations:
Painting is silent poetry, and poetry is painting with the gift of speech.
Painting is silent poetry, poetry is eloquent painting.
See also: Ut pictura poesis

"The Earth an Evolution", p. 35
The Universal Kinship (1906), The Physical Kinship

Source: The Letters of Gustave Flaubert, 1830-1857

Source: The Bell Jar

"The Letters of the Dead"
Poems New and Collected (1998), Could Have (1972)

Whether the Athenians were more Warlike or Learned, 3
Bartlett's Familiar Quotations, 10th ed. (1919)