Sail and steam ships of this age had quite inefficient engines (simple as opposed to compound) that had a high consumption of coal. So the engines were run for much less time than the ship would be under sail. But if it was calm, or for entering or leaving port you had the engine.

Many of these Glasgow ships were purpose-built blockade runners running into Confederate ports (with military supplies?) and taking out cotton. Of course, to avoid US cruisers you would need both sail and steam.

Of course your story-teller needs a reason to be leaning on the taffrail. He'd be an officer, or an apprentice officer, or perhaps a passenger of sufficient status. Astern he sees the wake and possibly following seabirds. Looking forrard he sees the mass of sails, if it's calm most or all of them, or if it's that calm and the engine is being used, clouds of thick black smoke. There's also the sounds and smells. Forrard he also sees the helmsman, the duty officer, and the men at work at the many large and small tasks to keep the ship both safe and clean.

Good luck with the song!