They reached the ramps that would launch them into the air, and shot off the end, Lyra and Crystal crying out in pain as the boulders crashed through their shields, but holding them long enough to alter their trajectory slightly. The right boulder flew directly at the nearest bridge, punching directly through the shield and hitting the edge of the wooden structure, smashing through most of it so that the barest bit of solid structure remained. It couldn't support the weight of the ponies on it, and snapped, throwing them into the river.