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Constantino Brumidi, 1805-1880, from "The Apotheosis of Washington," 1865, ceiling fresco in oculus of rotunda, U.S. Capitol Building, Washington, D.C.

The marine god Neptune directs the laying of the Transatlantic Cable with assistance from Amphitrite and various oceanic divinities (tritones), commemorating one of the great civil engineering projects of the American 19th Century. Over Neptune's head thirteen angelic persons represent the first 13 States/Colonies as they celebrate around George Washington in apotheosis. On the same level of the fresco as Neptune, other Olympians engage in the instruction of America. Neptune's peers are War=Lady Liberty (in lieu of Ares), Science=Athena/Minerva, Marine Arts=Poseidon/Neptune, Commerce=Hermes/Mercury, Mechanics=Hephaistos/Vulcan, Agriculture=Demeter/Ceres.

The image at right of Neptune is pretty much standard iconography — the hippocamps, triangular arrangement, nude Amphitrite, etc. — for triumphs of Neptune and Amphitrite from classical and neo-classical art. Making Neptune an engineer is pretty novel.
Note: the image at right is technically derived from Wikipedia, but it is used there in an undocumented copy from the Architect of the Capitol webpages. I have cropped it slightly for focus.