I too have family connections in Sutherland and Fife.  My great, great grandmother was Christian/Christina McLeod (1821-1877) and born in Dornoch.  She and James Fyfe (1810-1872; born in Kinghorn, Fife) married at Loth on 18 Feb 1848.  My question is: why would a soldier in the 93rd Regiment of Foot be in Helmsdale? Their marriage registration states the following: On the 18th of February 1848 were married James Fyfe Corporal 93rd Regiment of Foot, Helmsdale and Christian McLeod, Dornoch.  
 Is there a way to see if the Regiment was stationed in Helmsdale?  I have family in the area, but don't think any documents are kept locally any more.  Any ideas?