Ben Nevis the summit only to find "fragments of earthen and glass ware, chicken bones, corks, and bits of paper". It was not until 1847 that Ben Nevis was confirmed by the Ordnance Survey as the highest mountain in Britain and Ireland, ahead of its rival Ben Macdhui. The summit observatory was built in the summer of 1883, and would remain in operation for 21 years. The first path to the summit was built at the same time as the observatory and was designed to allow ponies to carry up supplies, with a maximum gradient of one in five. The opening of
Ben Nevis 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 (alpine) maritime (oceanic) Polar climate ("ET" climate in Köppen's classification). 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