Ferry county shall consist of the territory bounded as follows, to wit: Commencing at the point where the east boundary line of Okanogan county intersects the Columbia river; thence up the midchannel of the Columbia river to the mouth of Kettle river; thence up the midchannel of Kettle river to the boundary line between the United States and British Columbia; thence westerly along the said boundary line to the intersection thereof with the said east boundary line of Okanogan county; thence southerly along the said boundary line to the place of beginning.