"The clans were divided by blood feuds and animosities stretching back over centuries. Their members would serve only under their chiefs, and were quite as ready to come to blows with other clansmen as with the common enemy. MacDonalds from Glen Garry and Moidart would have nothing to do with Mackintoshes and Macphersons from Badenoch; Camerons from Lochaber were at permanent feud with the Frasers' MacLeans from the Isle of Mull looked with gravest suspicion at the MacNeils from the Isle of Barra, and so on."
A Letter From Rob Roy (referred to in the Tranter book - see link for the letter):
FROM Robert Campbell, alias M'Gregor, commonly called Rob Roy, To Field-Marshal Wade
Then receiving the submission of disaffected Chieftains and Clans.*
* ...published in the Appendix to an Edition of Burt's Letters from the North of Scotland, 2 vols. 8vo, Edinburgh, 1818.
Rob Roy by Sir Walter Scott (also referred to in the Tranter book).