I've got the book that that illustration appears in somewhere. The book was indeed written after the clearances and is the product of the Victorian romantic revision of highland culture, however, most of the equipment is drawn from genuine items in the collections of clan chiefs and the book contains a lot of anecdotes drawn from recent oral history. The highland archers are described as being inferior to their English counterparts, and their bows are described as being drawn to the chest and not the ear. Robert Bruce had archers in his army, but these archers, who were of some renown and skill apparently, were recruited from Ettrick forest. Apparently there is a very old bow in the Scottish national Museum in Edinburgh. Don't know if it's ancient or medieval. I must go and have a look at it.