The speaker says that, on the lake isle of Innisfree, peace will come "dropping slow," "Dropping from the veils of the morning to where the cricket sings." This suggests that the calm and tranquility that the speaker expects to find on the isle will descend upon him as if from the heavens. Although the poem is not explicitly religious, there is a suggestion here that such peace is a gift from above, a gift that has descended upon the natural world like an act of grace.
The slow, dropping quality of this peace emphasizes the stately rhythms of a life lived close to nature, which stands in stark contrast to the hustle and bustle of city life. It is from just such an urban environment, from the roadway and the "pavements grey," that the speaker wishes to escape by retreating to the haven of tranquility that is the lake isle of Innisfree.