The MacGregors verify this account of the feud by appealing to a proverb current amongst them, execrating the hour _( Mult dhu an Carbail ghil)_ that the black wedder with the white tail was ever lambed.

To avenge this quarrel, the Laird of MacGregor assembled his clan, to the number of three or four hundred men, and marched towards Luss from the banks of Loch Long, by a pass called _Raid na Gael,_ or the Highlandman's Pass.
Sir Humphrey Colquhoun received early notice of this incursion, and collected a strong force, more than twice the number of that of the invaders.

He had with him the gentlemen of the name of Buchanan, with the Grahams, and other gentry of the Lennox, and a party of the citizens of Dumbarton, under command of Tobias Smollett, a magistrate, or bailie, of that town, and ancestor of the celebrated author.
The parties met in the valley of Glenfruin, which signifies the Glen of Sorrow---a name that seemed to anticipate the event of the day, which, fatal to the conquered party, was at least equally so to the victors, the "babe unborn" of Clan Alpine having reason to repent it.

The MacGregors, somewhat discouraged by the appearance of a force much superior to their own, were cheered on to the attack by a Seer, or second-sighted person, who professed that he saw the shrouds of the dead wrapt around their principal opponents.

The clan charged with great fury on the front of the enemy, while John MacGregor, with a strong party, made an unexpected attack on the flank.