What kind of dreams is Mercutio describing, especially when he calls them "children of an idle brain

What is the rhyme scheme in this excerpt from longfellow's, "the tide rises, the tide falls? " (10 points) the tide rises, the tide falls, the twilight darkens, the curlew calls; along the sea-sands damp and brown the traveler hastens toward the town, and the tide rises, the tide falls.