A cargo of Florida sugar moved up the North River towards Yonkers Wednesday on the Sugar Express barge with the East Coast tug pushing. The Express was moving slowly against a ripping ebb tide bolstered by melting ice up north. But there was probably no rush, as the bulk ship which arrived at the plant earlier in the week with a load of Caribbean sugar would not leave the dock there for another few hours. Sugar Express waited in the anchorage near the plant and was delivered after the bulker left.