Abstract: In a hopper or the like wherein the flow of particulate material is controlled by a gate the improvement wherein the gate is mounted to be swingable towards an open position within the hopper so as to break arches and rat holes which form in the material above the gate or a gate adjacent thereto.

Abstract: A navigation channel is made in the ice covering the surface of a waterway by propelling a vessel so that its bow breaks the ice to form a channel having a width of the beam of the ship and an auxiliary channel is similarly formed at each side of the ship in rear of its bow to provide leeway for the ship to turn. As the ship is turned, the auxiliary channel is enlarged by breaking the ice on the edge of the auxiliary channel toward the stern of the ship to give it greater leeway to turn. The auxiliary channel may be broken out by fin means projecting from the side of the ship effective to exert forward, upward and outward force against the ice blanket to break pieces from it.