Unfortunately this tree was badly damaged by heavy snow and storms in December last year, but it's still an impressive tree.
The European hornbeam (Carpinus betulus) is found across Europe but is not native to Scotland. This individual was planted along with quite a few others along the Water of Leith specifically to produce timber for the mills that once lined the river (yes its hard to believe now, as you walk along the quiet wooded river in the Dells, but this was once the industrial centre of Edinburgh). The hornbeam was used a lot in construction because its wood is particularly hard.
The hornbeam has a fluted trunk, though the bark itself is smooth. It has fairly nondescript leaves (which are just in bud at the moment, but the photos didn't come out!) but has beautiful catkins that grow in the summer and last through to early winter. They look like mini-chandeliers.