A captain, a hired expert and the coming of evening are all the poem gives us, and it leaves us to work out the rest. The title, "Consultant," tells us the "her" of the second line is probably someone brought in for her knowledge. The captain, by contrast, is a figure of command. Yet at the hour when the sun stands highest and shadows are shortest, he asks to be taught about the end of the day. The central idea seems to be that authority has limits. Even someone used to giving orders must learn to read what is coming, and what is coming cannot be commanded.
The word "would" in the second line matters. "Would have her teach" suggests a habit or a wish rather than a single event. It could be something the captain does day after day, or something he intends, so the scene hangs between routine and hypothesis. The poem never says whether the lesson happens, and that uncertainty keeps it open.
The phrase "the mathematics of evening" is the poem's most surprising choice. It is the longest, most abstract phrase in a text otherwise made of plain, concrete words, and it promises numbers, angles and calculation. The dash that follows then withholds them. What comes next is a list of things seen: "the red land, the coursing water, / a moth in clear daylight / rising early." The poem seems to suggest that this is what the mathematics of evening really consists of, a set of signs read by eye rather than a set of figures. Colour, movement and one small anomaly add up to a sum the captain needs to understand. Judging by the imagery, evening here may also stand for something larger, an ending or a change of conditions, though the poem never says so.
The images are chosen carefully. "The red land" suggests ground lit by a low sun, or perhaps earth that is simply red. Either way, it is the poem's only colour, and it glows against the pale noon of the opening. "Coursing water" brings in motion. The participle gives the water a purpose and a direction, as if it were running somewhere ahead of the light. Then comes the moth, the smallest and strangest item in the list. Moths belong to dusk and night, so one flying in "clear daylight" is out of place and acts as a premature messenger. The word "clear" is worth noticing, because nothing about the day looks threatening. The warning is tiny, easy to miss, and visible only to someone who knows what to look for. That, presumably, is what a consultant is for.
The poem has no rhyme and no regular metre. It is free verse, built from short lines of roughly four to eight syllables. Still, the sound is carefully managed. The first two lines are almost identical in length and rhythm, which gives the opening a steady, official tone, like a command being issued. The lines then lengthen and loosen into the list, and the poem finishes on its shortest line, "rising early." The enjambment is what makes this work. The verb "rising" is held back at the start of the last line, so the moth lifts off in the white space after "daylight." Meanwhile the "r" of "red" returns in "rising," and the "ear-" of "early" echoes the "eve-" of "evening," quietly tying the end of the poem back to its subject.
The structure is also a single sentence. It begins with the captain's noon and ends on the word "early," so the grammar itself runs ahead of the clock, from midday toward dusk without stopping. There is no commentary and no explanation, only a scene and a list.
What makes the poem worth reading is how much it does with so little. It sets up a hierarchy, with a captain who commands and a consultant who knows, and then quietly reverses it, because the knowledge that matters concerns light and water and an insect, which no captain controls. It also treats attention as a kind of calculation. By asking us to see a moth as a figure in an equation, the poem suggests that noticing small things, and understanding when they are out of place, may be a form of precision as serious as any arithmetic.