Their intended journey was described by Mendelssohn in a letter home from Edinburgh on 28 July.
Felix Mendelssohn – letter, Edinburgh, 28 July 1829:
The Highland journey will be as follows: via Stirling, Perth, Dunkeld, and the waterfalls to Blair Atholl; thence on foot over the hills to Inverary, to Glencoe, the Isle of Staffa, and the Isle of Islay; there a stay of several days will be made, because Sir Alexander Johnston has sent after me a letter of introduction to Sir Walter Campbell, the lord, owner, and tyrant of the island, whom a word of Johnston’s tames and turns into a willing guide. From thence up the Clyde to Glasgow, then to Ben Lomond, which with the Loch Lomond forms the Highland Lion, to Loch Earn, Ben Voirlich, Loch Katrine; then to Cumberland.
In fact they never got as far as Islay; perhaps they ran out of time, or perhaps Felix’s experience of being sea sick on their trip to see the Isle of Staffa was enough to put him off another ferry journey to a Hebridean island! Their actual route once they reached Scotland can be seen on the map below.