A 3 stanza poem, each from a different point in history. It talks about the different civilizations as time passes by.
Stanza one's ship is a quinquireme, a large vessel which people like the ancient Phoenicians employed to trade across the Mediterranean Sea. These ships were propelled both by the wind and by men rowing. This boat carries a cargo of animals, birds, exotic woods, and wine.
In Stanza two, the poem moves ahead about two thousand years to the sixteenth or seventeenth century and changes its focus to the West Indies. Its cargo contains precious (emeralds and diamonds) and semi-precious stones, spices, and gold coins.
In Stanza three, the British ship is not so pretty as the previous two (it is "dirty") nor so big. It moves through the English Channel with a force and motion that resembles an animal's butting with its head. Part of its cargo are things to burn: wood for fireplaces and coal mined near Newcastle-upon-Tyne on the eastern coast of Britain. The rest is metal that has been processed or manufactured, metal rails with which to build railroad tracks, lead ingots or "pigs," items of hardware made of iron, and "cheap tin trays."
The speaker encounters a black snake at "his" water trough. Rapt by nearly hypnotic fascination, he allows the snake to drink, without taking action. The speaker wonders whether he is a coward not to kill the snake, because in Sicily the gold snakes are venomous. The snake continues to drink until, satisfied, it climbs the broken bank of the wall face, puts its head into "that dreadful hole," and withdraws "going into blackness." At this point, the speaker throws a log at the water trough yet fails to hit the snake. Immediately, he regrets his "pettiness" and wishes that the snake would come back, for it seemed to be like a king. The speaker has missed his chance with "one of the lords of life."