On the north-east the principal heights are Ben Slioch (3217 ft.), whose sugar-loaf form dominates the landscape, Ben Lair (2817) and Ben Airidh-a-Char (2593), and, on the south-west, the peaks of Ben Eay, four of which exceed 3000 ft.
The reburnt and cooled char is collected and sent back to the char cisterns.
In the best-appointed refineries the whole of the work in connexion with the char is performed mechanically, with the exception of packing the filter cisterns with fresh char and emptying the spent and washed char on to the carrying bands.
The sea pierces the islands in deep fjords, or separates them by narrow inlets through which tidal currents set with great violence, at speeds up to seven or eight knots an hour; and, as communications are maintained almost wholly by boat, the natives have need of expert watermanship. There are several lakes in which trout are abundant, and char also occur; the largest is Sdrvaag Lake in Vaagd, which is close to the sea, and discharges into it by a sheer fall of about 160 ft.
In diameter, which afforded the first indications of the spiral structure shown in recent photographs to be the most prevalent char- Lord acteristic of nebulae.