Desiring to open the Northern Pacific to travel and traffic a year earlier than was possible if they waited for the completion of the huge tunnel through the Cascades, a great passage blasted through the mountains ninety-eight hundred and fifty feet in length, the officers decided to construct a line over the summit on the “switchback” principle, at a cost of $300,000.00. It was completed early in the summer of 1887, having seven miles of track and an average grade of nearly three hundred feet to the mile. Huge decapod (ten drive wheels) locomotives were built for this service, the most powerful ever constructed. Two decapods are used, one at each end of the short train. The bottom line of the diagram represents the main track at the mouth of the tunnel. The train moves ahead until it passes the switch S, and then moves backward and upward until it passes the next switch, thus alternating until the summit is gained, when it descends on the opposite side in the same manner. The general principle of the “switchback” is clearly shown in the following diagram: