Ben Nevis. Ben Nevis is the highest mountain in the British Isles. Standing at 1,345 metres above sea level, it is at the western end of the Grampian Mountains in the Lochaber area of the Scottish Highlands, close to the town of Fort William. The mountain is a popular destination, attracting an estimated 100,000 ascents a year, around three-quarters of which use the Pony Track from Glen Nevis.The 700-metre cliffs of the north face are among the highest in Scotland, providing classic scrambles and rock climbs of all difficulties for climbers and mountaineers. They are also the principal locations in Scotland for ice climbing. The summit, which is the collapsed dome of an ancient volcano, features the ruins of an observatory which was continuously staffed between 1883 and 1904. The meteorological data collected during this period are still important for understanding Scottish mountain weather. C. T. R. Wilson was inspired to invent the cloud chamber after a period spent working at the observatory. Ben Nevis is an Anglicisation of the Scottish Gaelic name Beinn Nibheis. Beinn is the most common Gaelic word for mountain, Nibheis is variously understood, though the word is commonly translated as malicious or venomous. An alternative interpretation is that Beinn Nibheis derives from beinn nèamh-bhathais, from nèamh heavens, clouds and bathais top of a man's head. One translation would therefore be the mountain with its head in the clouds, though mountain of Heaven is also frequently given. As is common for many Scottish mountains, it is known both to locals and visitors as simply the Ben. Ben Nevis forms a massif with its neighbour to the northeast, Càrn Mòr Dearg, to which it is linked by the Càrn Mòr Dearg Arête. Both mountains are among the nine in Scotland over 4,000 feet; Aonach Beag and Aonach Mòr are also on the Nevis massif. The western and southern flanks of Ben Nevis rise 1,200 metres in about 2 kilometres above the River Nevis flowing down Glen Nevis-the longest and steepest hill slope in Britain-with the result that the mountain presents an aspect of massive bulk on this side. To the north, by contrast, cliffs drop some 600 metres to Coire Leis A descent of 200 metres from this corrie leads to the Charles Inglis Clark Memorial Hut, a private mountain hut 680 metres above sea level, owned by the Scottish Mountaineering Club and used as a base for the many climbing routes on the mountain's north face. The hut is just above the confluence of Allt a' Mhuilinn and Allt Coire na Ciste. In addition to the main 1,344.527-metre summit, Ben Nevis has two subsidiary tops listed in Munro's Tables, both of which are called Càrn Dearg. The higher of these, at 1,221 metres, is to the northwest, and is often mistaken for Ben Nevis itself in views from the Fort William area. The other Càrn Dearg juts out into Glen Nevis on the mountain's southwestern side. A lower hill, Meall an t-Suidhe, is further west, forming a saddle with Ben Nevis which contains a small loch, Lochan Meall an t-Suidhe. The popular tourist path from Glen Nevis skirts the side of this hill before ascending Ben Nevis's broad western flank. Ben Nevis is all that remains of a Devonian volcano that met a cataclysmic end in the Carboniferous period around 350 million years ago. Evidence near the summit shows light-coloured granite lies among dark basaltic lavas. The two lying side-by-side is evidence the huge volcano collapsed in on itself creating an explosion comparable to Thera or Krakatoa.The mountain is now all that remains of the imploded inner dome of the volcano.Its form has been extensively shaped by glaciation. Research has shown igneous rock from the Devonian period intrudes into the surrounding metamorphic schists; the intrusions take the form of a series of concentric ring dikes. The innermost of these, known as the Inner Granite, constitutes the southern bulk of the mountain above Lochan Meall an t-Suidhe, and also the neighbouring ridge of Càrn Mòr Dearg; Meall an t-Suidhe forms part of the Outer Granite, which is redder in colour. The summit dome itself, together with the steep northern cliffs, is composed of andesite and basaltic lavas. Ben Nevis has a highland maritime polar climate. Ben Nevis's altitude, maritime location and topography frequently lead to cool and cloudy weather conditions, which can pose a danger to ill-equipped walkers. According to the observations carried out at the summit observatory from 1883-1904, fog was present on the summit for almost 80 per cent of the time between November and January, and 55 per cent of the time in May and June.