Other mistake: Halfway in the first fight scene, Montrose "confesses" to Argyll about his weariness, as the POV changes there is a heavy blurry skip at the top of the screen. (00:15:24)
Other mistake: In the scene around the camp fire, Rob Roy can be clearly seen with with plasters on his hand.
Answer: Cow patties leaving the cow and plopping on the ground leave a distinctively odor and start to harden up after a certain length of time. It isn't to hard to speculate that, since these are cattlemen by trade, they would have a systematic way of knowing how long it would take for a cow pie to harden & lose it's odor. Example: they would know that a cow pie left out for 2 days would lose half it's odor & become semi-hard but still have a mushy center.
CCARNI ★