A West Highland Line crosses the Glenfinnan Viaduct, with Loch Shiel in the background. (Norman McNab)

My first glimpse of the West Highland Line comes before I board the train. I’ve just bought a newspaper from a shop outside Glasgow Queen Street Station, and there it is, in with my change: the stately, sweeping curve of the Glenfinnan Viaduct set against a mountainous Highland background — on the back of a Scottish 10-pound note.

Details: West Highland Line

A good omen, surely, for a trip on which the promise of magnificent countryside will go hand in hand with the reality of looking after a 22-month-old boy on a train for five hours. My wife and I are heading to Arisaig, on Scotland’s west coast, for my brother’s wedding, and we’ve decided to take the slow train from Glasgow. Magnificent, I’d repeatedly heard from friends and family, but hard work with a toddler — especially since, rather optimistically, I’m planning to make some final amendments to my best-man’s speech en route.

As we arrive at the station, it’s buzzing with activity. It’s Friday lunchtime, and everywhere you look there are groups of people — tourists, weekenders and locals — with suitcases and bicycles and plastic bags bulging with sandwiches and beer cans. The sound of excited chatter reverberates around the station, a high-roofed shed yards from George Square, Glasgow’s huge central plaza. “Run in the station and your next stop could be [the ER],” bellows a huge billboard in front of the trains: There seems little risk of that, given the relaxed ambiance.

Aboard the train, the atmosphere is similarly bright, even if the conditions aren’t exactly Orient Express plush. The seats on this four-carriage train are small, to put it bluntly, and our carriage is very nearly full: I’m competing for leg space with the friendly Australian woman sitting opposite me. We eventually come to an accord, but for those trying to pass each other in the corridor, negotiations prove rather more protracted: Letting someone through with a bag in hand requires the flexibility of an Olympic gymnast.

No one seems to mind too much, however. My wriggling son ensconced on my knee, I stare out the window as the train moves off. Initially, there isn’t much to look at: the gray-brown brick wall of a Glasgow railway tunnel, a stern red tenement block, estates full of box-shaped houses. As the city begins to give way to lush greenery, though, there’s a foretaste of the Highlands: a warehouse owned by whisky distillers Morrison Bowmore, with barrel upon barrel piled up in the yard.

My son is less interested than I in all this. Before I can stop him, he’s in the aisle, looking for a bit more excitement, smiling and chatting with his fellow passengers. In some places, this would have meant scowls and tuts — but Glasgow, despite its formidable reputation (the city is scarred by religious sectarianism, most evident in the soccer rivalry between Catholic Celtic and Protestant Rangers), is a friendly place, and he meets mostly smiles and winks before his recapture.

Outside, the scenery is improving: the Clyde, the river that runs through Glasgow and the source of the city’s historical significance, is at low tide, and its retreat has exposed a pleasingly wide expanse of red-brown mud.

At Dumbarton, my wife takes my son up the carriage to see whether he’ll go to sleep in her arms. No luck. A soldier in full military fatigues — including a purple-blue feather in his beret, a sign that he’s a member of one of Scotland’s two reserve regiments — is one of the few people to get on. “Oh my goodness,” he says to my wife. “If you’ve no’ got a seat, I’ve got no chance!” Overhearing the conversation, a man nearby points at the seat beside him: “Don’t worry. There’s one here!”

Soon enough, it’s my turn to try to rock my son to sleep. By now, we’re gliding along the side of Gare Loch, and squatting slightly to see out the window, I catch a glimpse of HMNB (Her Majesty’s Naval Base) Clyde, where Britain’s nuclear submarines are docked. It’s an incongruous site amid the bluebells, the tree-lined slopes and the brooding brown-green hills.

Across the moor

My son — at last — is slumbering, but the atmosphere on board is heating up. Loch Lomond is coming into view, but it’s something else that’s causing a commotion. A group of four whoops with delight at the sound of another man’s ringtone: It’s “Smoke on the Water,” a rock anthem from the not-quite-forgotten Deep Purple. Closer to us are two girls, students, who are sipping lager as they discuss a third student. “Where’s he from? Argentina?” one asks with a smile. The atmosphere is part school-bus trip, part Glasgow pub.

The students tumble off the train at Arrochar and Tarbet, one hour into our trip. A shame for them, perhaps, because the best is still ahead. Just past the station, the train plunges through a verdant tunnel of trees before emerging into a panoply of colors that belie our northerly location. There’s the stern gray rock, of course, but also fields of bluebells, streams rushing down steep green banks, yellow-tipped gorse and even some shaggy brown Highland cattle here and there. And what’s that? It looks suspiciously like a glimpse of blue sky.

At Crianlarich, we stop for five minutes. The train divides here: two carriages go to Oban, the other two (including us) farther north to Mallaig. “Anyone who smokes, get off here,” a man with an earring — the same one with the Deep Purple ringtone — tells the carriage. Plenty take his advice.

And then we’re off again, the train rattling along on the jointed rails: clackety-clack, clackety-clack, clackety-clack. I find myself looking from side to side as remarkable view follows remarkable view. It’s quickly becoming clear to me why so many people advised us to take the train and why it was voted the top rail journey in the world by readers of the independent British travel magazine Wanderlust in 2009.

One of the most interesting and quirky aspects of the line comes just north of Tyndrum. Here the train takes a horseshoe curve around a broad valley, offering views of two huge, conical hills, Beinn Odhar and Beinn Dorain, before heading back in the direction it had come from and then turning north.

And then there’s Rannoch Moor, a unique and rather spooky place. It’s a lumpy, boggy stretch of country pockmarked with rocky outcroppings and tiny streams. The train tracks are laid on a mattress of turf, ash and brushwood over the soft, yielding peat. It’s alive with creatures both great and small and as close to wilderness as Britain gets: Corrour, one of the stations on the moor, is more than 10 miles from a public road.

Indeed, the station exists only because Sir John Stirling-Maxwell, the aristocratic landowner at the time the railway was built in the late 1800s, insisted on its construction for the benefit of his guests in return for allowing the railway to cross his property. A scene in the 1996 film “Trainspotting” occurs here as the central character, Renton, delivers an impassioned, vodka-fueled dissection of the Scottish people’s shortcomings.

You can understand how Rannoch might get you down a bit, but what comes next lifts the spirits: the startlingly beautiful Loch Treig. The line runs along the loch’s eastern bank, and the carriage noticeably quietens as we stare across the blue-gray water toward the imposing green bank on the opposite side. Suddenly, the train slows, and looking out the window I can see why: There, on the steep slope down toward the loch, lies an overturned train engine, a reminder that not all Highland days are as gentle as this one.

Impossible romance

Fort William, the largest town in this part of the Highlands, marks a turning point on our journey. It lies in the shadow of Ben Nevis, Britain’s highest mountain, and it’s here that the sleeper from London — which runs every night except Saturday — terminates and the Jacobite, a daily tourist steam service, makes the run up to Mallaig, a busy fishing town where you can catch a ferry to the islands between May and October.

A first-class round-trip ticket on the Jacobite is 56 pounds (about $74), about the same as it has cost me to get all the way to Arisaig from Glasgow. The Jacobite’s for the steam-train fetishists, I think, especially since the views from our train can surely be no worse. A perfect example comes shortly after Fort William, when we pass close to the impressive Neptune’s Staircase, a neat series of 19th-century locks on the Caledonian Canal.

My son has awakened, although he doesn’t seem that interested in canals or brooding Scottish mountains: He’d rather watch an episode of “Postman Pat,” a British children’s cartoon about, well, a postman called Pat, on his mother’s iPad. Meanwhile, in the seats beside us, a new conductor, who got on at Fort William, has sat down to have a chat with what appear to be regular customers. They must be, because they hardly look up when we stop at Corpach Station, which is festooned with tulips, or at the bluebells that cover vast swaths of otherwise green-black mountainside.

And then comes the marvel on the 10-pound note: the Glenfinnan Viaduct. Our train slows almost to a halt as we approach, and I lean to the left to get a better view. It’s an almost impossibly romantic spot. Built entirely in concrete, the bridge consists of 21 arches; Loch Shiel stretches away to the south, the River Finnan valley to the north. Down by the loch, there’s the Glenfinnan Monument, which marks the spot where Bonnie Prince Charlie raised his standard and began the Jacobite Rising in 1745.

Given its extraordinary elegance, it’s no surprise that the viaduct was used in three of the Harry Potter films. The station just after (Glenfinnan) boasts a museum devoted to the railway line, but we’re on the homestretch now and, charming as this trip has been, the prospect of a lengthy wait for the next train does not appeal. And anyway, there’s still more to surprise and delight: As we pass Loch Eilt (which boasts numerous strange little wooded islands), it almost feels as if you could lean over and trail your fingers in the icy-blue water.

After a glimpse of the abandoned, rather careworn hilltop Church of Our Lady of the Braes, there’s the first sight of the sea just before we reach Beasdale. The train doesn’t stop at Beasdale, though: So few passengers get on and off it here that it’s a request stop, and clearly today there have been no requests.

Finally, five hours after leaving Glasgow, there’s Arisaig. The train actually calls at two more stops (Morar and Mallaig), but the wedding is here, and anyway, it seems a suitable place to end a journey into the Western Highlands: This is the westernmost station in Britain.

As we stumble off, toddler and numerous bags in tow, I realize that I haven’t gotten much work done on that best-man’s speech. There just wasn’t time.

Hawkes is a freelance writer in London.