give an explanation of these lines 'Half-flush that dies along her throat:' such stuffWas courtesy, she thought, and cause enoughFor calling up that spot of joy. She hadA heart -- how shall I say? -- too soon made glad,Too easily impressed; she liked whate'erShe looked on, and her looks went everywhere.Sir, 't was all one! My favour at her breast,The dropping of the daylight in the West,The bough of cherries some officious foolBroke in the orchard for her, the white mule ....
The speaker in the poem "My Last Duchess" is presumably the Duke, her husband. Throughout the poem, he expresses his displeasure at the young lady's joy. She finds joy in things like a sunset ("the dropping of the daylight...) and cherries from an orchard. For the Duchess, these were simple things of beauty, and worthy of her joy. It might also be assumed that she is blissfully unaware of the Duke's unhappiness.
The Duke, in turn, appears to harbor some jealously, not only at the "officious fools" who bring her cherries, but also towards innocent symbols of joy such as the sunset. For the Duke, the money and pleasure that he provides her should be the only things that make the Duchess happy.
The fact that these do not take priority in her pleasure drives the Duke to distraction, and he meticulously lists everything that makes her heart glad "too soon" and that calls that "spot of joy" to her cheek. In short, he is jealous and past the verge of letting this jealously get the better of him.
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