In the statement of the boundaries in this article:
1. "To," "on" or "along" a mountain range or mountains means the summit point or summit line of the mountain range of mountains.
2. "Up" or "down" a creek or river means the middle of the main channel thereof.
3. "Mouth" of a creek or river or "junction" of a creek or river with a river is the point where the middle of the channel of each intersects the other.