LOC Printers' Marks, Latin and Greek Mottos

Library of Congress, November 2009. Two early printers' marks painted on the ceiling of the Jefferson Building.

On the left, D. Appleton & Co. (note D A & CO on the shield). The Latin inscription in the ribbon reads INTER FOLIA FRUCTUS (fruit among the leaves) = e.g., the  "leaves" (i.e., pages of book) yield "fruit" (knowledge).

On the right, the De Vinne Press. The Greek inscription is a citation from "Prometheus Bound" (Προμηθεύς δεσμώτης), a tragedy by Aeschylus (Αἰσχύλος):

καὶ μὴν ἀριθμόν, ἔξοχον σοφισμάτων,
ἐξηῦρον αὐτοῖς γραμμάτων τε συνθέσεις,
μνήμην ἁπάντων, μουσομήτορ᾽ ἐργάνην. (Fragment β' lines 459-61)

[Prometheus speaks here: "Yes, and numbers, too, chiefest of sciences, I invented for them (humans), and the combining of letters, creative mother of the Muses' arts, with which to hold all things in memory."]

If you're interested, you can take a look at the original Greek text and an English translation.