The following four paragraphs are from Under the Sea Wind: A Naturalist’s Picture of Ocean Life (1941) by Rachel Carson. I have added punctuation to them to help with flow and clarity, as was the goal of the assignment.
“To stand at the edge of the sea – to sense the ebb and flow of the tides, to feel the breath of a mist moving over a great salt marsh, to watch the flight of shore birds that have swept up and down the surf lines of the continents for untold thousands of years, to see the running of the old eels and the young shad to the sea – is to have knowledge of things that are as nearly eternal as any earthly life can be.”
“Before sunset, the skies lightened and the wind abated; while it was yet light, the sanderlings left the barrier island and set out across the sound beneath them. As they wheeled over, the inlet was the deep, green ribbon of the channel that wound, with many curvings, across the lighter shallows of the sound. They followed the channel: passing between the leaning, red spar buoys, past the tide rips where the water streamed broken into swirls and eddies, over a sunken reef of oyster shell, and came at last to the island there they joined a company of several hundred white-rumped sandpipers – least sandpipers and ring-necked plovers – that were resting on the sand.”
“While the tide was still ebbing, the sanderlings fed on the island beach. As they slept, and as the earth rolled from darkness toward light, birds from many feeding places along the coast were hurrying along the flyways that led to the north; for with the passing of the storm, the air currents came fresh again and the wind blew clean and steady from the southwest. All through the night, the cries of curlews and plovers and knots, of sandpipers and turnstones and yellowlegs, drifted down from the sky. The mockingbirds who lived on the island listened to the cries: the next day they would have many new notes in their rippling, chuckling songs to charm their mates and delight themselves.”
“About an hour before dawn, the sanderling flock gathered together on the island beach where the gentle tide was shifting the windrows of shells. The little band of brown-mottled birds mounted into the darkness and, as the island grew small beneath them, set out toward the north.”
In the first paragraph, the dashes were added because the middle chunk of the paragraph all felt like an aside, like an addition to the two end caps of the paragraph. The middle thoughts felt like they built on each other, so each were separated by commas to help them build to the end of the descriptions within the paragraph. They could also be taken out and still have a complete thought for the sentence. The middle two paragraphs contained more detailed descriptions, demonstrating the channel and the journey of the sanderlings. Commas were added to differentiate the different thoughts in the paragraphs. After “channel” in the second paragraph, a colon was added because the following seemed like a descriptive list, and it places more of an emphasis on what follows. The paired dashes in that paragraph add separation and descriptions to the bird types. The semicolon in the third paragraph was added to break the two thoughts, because they felt too similar and connected to completely separate them into two sentences. The colon in the last sentence elucidates the clause proceeding it. The final paragraph felt like two sentences, broken between “shells” and “the.” Other than that addition, a few commas were added for overall clarification.