Half Ben Nevis

The half-way lochan and the great north corrie of Nevis.

Distance 10 miles (16.1km)

Minimum time 6hrs 15min

Ascent/gradient 2,000ft (610m)

Level of difficulty Hard

Paths Hill paths, well-built, then very rough, 6 stiles

Landscape Slopes of Britain's biggest hill

Suggested map aqua3 OS Explorer 392 Ben Nevis & Fort William

Start/finish NN 123731

Dog friendliness On leads through Achintee grazings, by River Nevis

Parking Large car park at Glen Nevis Visitor Centre

Public toilets At start

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Directions
Background
Information

1 At the downstream corner of the car park, a bridge signed 'Ben Path' crosses the River Nevis. The path turns upstream, crossing fields to join the Mountain Trail (formerly known as the Pony Track) to Ben Nevis. After a long climb, a notice points you to a zig-zag up left on to the half-way plateau. The path passes above Lochan Meall an-t-Suidhe, the Halfway Lochan, down on the left.

2 The main path takes a sharp turn back to the right, heading for the summit. Your smaller path descends ahead, behind a wall-like cairn. Soon it climbs gently over peat bog to a cairn on the skyline. Here it becomes rough and rocky as it slants down across the steep slide slope of the valley of Allt a' Mhuilinn. Eventually it joins the stream and runs up beside it to the Charles Inglis Clark (CIC) Hut.

3 Return for 100yds (91m) and cross the stream on the right to join a clear path which leads downhill. This descends a rocky step with a waterslide and reaches a ladder stile into plantations.

4 Go down a forest road and where it bends left over a bridge, keep ahead down a rough path. This stays beside the stream to a ladder stile at the railbed of the old aluminium railway. Turn left for ½ mile (800m), when a side-track joins from the left and the track passes under power lines. In another 220yds (201m) take a smaller track on the right that rejoins the Allt a' Mhuilinn. Keep to the right of distillery buildings to reach the A82.

5 Cross the River Lochy on Victoria Bridge opposite and turn left into a fenced-off side road and left again along a street. It rises to a railway bridge. Turn left here on to a long footbridge back across the Lochy. At its end, turn right over a stile for a riverside path. This passes to the right of a rugby ground, then becomes a built path into woodland. After two footbridges, bear left on a smaller path to the edge of Inverlochy. Turn right, then left into a street with copper beeches. This leads through Montrose Square to the A82.

6 The street opposite is signed 'Ben Nevis Footpath'. Shortly, take a stone bridge to the Glen Nevis road. Turn left for ¼ mile (400m) to a track on the left. Recross the Nevis on a green footbridge and turn right to a lay-by marked 'No Overnight Parking'. Just beyond this a small riverside footpath leads up-river to the footbridge at Glen Nevis Visitor Centre.

For 21 years in the 19th century, an observatory was sited on the summit of Ben Nevis. It recorded, to the surprise of few, that this is one of the wettest spots in Britain. Averaged over the year, the summit is sunny for about two hours per day.

This walk of half the hill shows you the mountain's great northern crags and the rocky hollow of Coire Leis. The further edge of the corrie is the jagged line of Tower Ridge, Britain's longest rock climb. In early spring the damp Atlantic winds coat the crags in thick hoar-frost, over which climbers with crampons and ice axes have created hundreds of routes.

Charles Wilson, a grammar school teacher turned Cambridge professor, came to Ben Nevis on holiday in 1894. The Scottish-born professor was so struck by the effects of sunlight on the clouds above Coire Leis that he attempted to reproduce them in the Cavendish Laboratory. In so doing he invented the Wilson cloud chamber, for which he was awarded the Nobel Prize for Physics in 1927.

In summer, the moist Atlantic air that sweeps into Coire Leis condenses into cloud, and then rain. Each droplet forms around a 'nucleation centre' such as a speck of dust. Perfectly clean air can become supersaturated: it has more than enough moisture to form clouds, but can't. When moist air rises up Ben Nevis it expands due to the drop in pressure. As it expands it cools, allowing the water droplets to appear. In Wilson's Cloud Chamber, the pressure drop was achieved by means of a bicycle pump working backwards. One pull of the pump handle, and any passing particle became suddenly visible as a pencil-line of white cloud. The step-up in size is astonishing: it's as if a small model aeroplane left a vapour trail as wide as the solar system and visible to an observer on another star!

Cosmic rays - high energy particles from outer space - can be seen zipping through the cloud chamber. Thus the positron (the positive electron) was discovered in 1932 and the muon (an exotic heavy electron) in 1937. It is actually possible to make your own Wilson cloud chamber - simply cool air with dry ice and shine a torch in. The successor to the cloud chamber was devised while gazing into a glass of beer. Donald Glaser earned the Nobel Prize for his bubble chamber in 1960.

While you're there

From Fort William's Town Pier, a passenger ferry across Loch Linnhe lets you explore the woods of Camusnagaul. Longer cruises visit the fish farms and seal island, while the evening cruise along Loch Eil gives, if it's clear, the best views of Ben Nevis' great northern corrie.

Where to eat and drink

The Ben Nevis Inn, at the bottom of the Mountain Trail, offers food and music to returning walkers. It's the local of the Lochaber mountain rescue team, and featured in the BBC programme Rockface. Children are welcome, and dogs in the beer garden. The walk also passes Nevisport (at the north end of Fort William, with a bar and café) and the Nevis Takeaway, Inverlochy.