Whatcom county shall consist of the territory bounded as follows, to wit: Commencing on the forty-ninth parallel at the point dividing the American and British possessions in the Gulf of Georgia; thence along said boundary line to where it deflects at the north entrance to the Haro Strait; thence along the northeasterly boundary of San Juan county to the ninth standard parallel, or the northwest corner of Skagit county; thence due east along said parallel to the summit of the Cascade mountains; thence northerly along the summit of said mountains to the forty-ninth parallel of north latitude; thence west along said parallel to the place of beginning.