The velocities and spatial distribution of high- and intermediate-velocity neutral hydrogen gas in the second quadrant of Galactic longitude in the northern hemisphere are accounted for in terms of a model in which the clouds appear to be part of a vast supershell with an elliptical cross section normal to the Galactic disk. Its origin appears to be in the Perseus arm toward l=131°±4° with an apparent radius of 1920 pc and an expansion velocity of 281±10 km s −1 . The supershell is treated, to first order, as an elongated structure coaxial with the Perseus spiral arm in order to facilitate comparison between available high-velocity cloud (HVC) velocities and the model