1. A RAILWAY HOPPER CAR BODY OF ELONGATED BOX-LIKE FORM COMPRISING A ROOF HAVING AN ELONGATED LONGITUDINALLY EXTENDING SUBSTANTIALLY RECTANGULAR HATCH OPENING IN THE CENTRAL PORTION THEREOF THROUGH WHICH LADING IN FINELY DIVIDED CONDITION MAY BE LOADED INTO SAID BODY, A SUBSTANTIALLY RECTANGULAR COAMING CARRIED BY SAID ROOF AND SURROUNDING SAID HATCH OPENING AND PROVIDED WITH A RIM SURROUNDING THE OPEN TOP THEREOF, A COMPOSITE COVER CARRIED BY SAID ROOF AND COOPERATING WITH SAID RIM AND INCLUDING A PAIR OF END COVER SECTIONS AND A NUMBER OF INTERMEDIATE COVER SECTIONS ARRANGED IN CONTIGUOUS LONGITUDINAL POSITIONS WITH RESPECT TO EACH OTHER, FIRST MEANS MOUNTING SAID END COVER SECTIONS UPON SAID ROOF FOR INDEPENDENT HINGED MOVEMENTS LATERALLY OF SAID HATCH OPENING AND BETWEEN OPEN AND CLOSED POSITIONS WITH RESPECT TO THE RESPECTIVELY ADJACENT END PORTIONS OF SAID RIM, SECOND MEANS MOUNTING SAID INTERMEDIATE COVER SECTIONS UPON SAID ROOF FOR INDEPENDENT HINGED MOVEMENTS LATERALLY OF SAID HATCH OPENING AND BETWEEN OPEN AND CLOSED POSITIONS WITH RESPECT TO THE RESPECTIVELY ADJACENT INTERMEDIATE PORTIONS OF SAID RIM, WHEREIN SAID COMPOSITE COVER CLOSES SAID HATCH OPENING WHEN ALL OF SAID COVER SECTIONS OCCUPY THEIR CLOSED POSITIONS, A PAIR OF END CLAMPS CARRIED BY SAID ROOF AND RESPECTIVELY COOPERATING WITH THE ADJACENT OUTER ENDS OF SAID END COVER SECTIONS, THIRD MEANS MOUNTING SAID END CLAMPS UPON SAID ROOF FOR INDEPENDENT HINGED MOVEMENTS LATERALLY OF SAID HATCH OPENING AND BETWEEN CLAMPING AND RELEASING POSITIONS WITH RESPECT TO THE OUTER ENDS OF THE RESPECTIVELY ADJACENT ONES OF SAID END COVER SECTIONS IN THEIR CLOSED POSITIONS, A PLURALITY OF INTERMEDIATE CLAMPS CARRIED BY SAID ROOF AND RESPECTIVELY COOPERATING WITH ADJACENT ONES OF THE PAIRS OF CONTIGUOUS ENDS OF SAID COVER SECTIONS, FOURTH MEANS MOUNTING SAID INTERMEDIATE CLAMPS UPON SAID ROOF FOR INDEPENDENT HINGED MOVEMENTS LATERALLY OF SAID HATCH OPENING AND BETWEEN CLAMPING AND RELEASING POSITIONS WITH RESPECT TO THE RESPECTIVELY ADJACENT ONES OF THE CONTIGUOUS ENDS OF TWO OF SAID COVER SECTIONS IN THEIR CLOSED POSITIONS, WHEREIN ANY ONE OF SAID COVER SECTIONS IS RELEASED FOR HINGED MOVEMENT BETWEEN ITS CLOSED POSITION AND ITS OPEN POSITION IN RESPONSE TO HINGED MOVEMENTS OF BOTH OF THE RESPECTIVELY COOPERATING TWO OF SAID CLAMPS FROM THEIR CLAMPING POSITIONS INTO THEIR RELEASING POSITIONS, AND A PLURALITY OF FASTENING MECHANISMS CARRIED BY SAID ROOF AND RESPECTIVELY COOPERATING WITH ADJACENT ONES OF SAID CLAMPS, EACH OF SAID FASTENING MECHANISMS BEING SELECTIVELY OPERATIVE BETWEEN HOLDING AND RELEASING POSITIONS WITH RESPECT TO THE ADJACENT COOPERATING ONE OF SAID CLAMPS IN ITS CLAMPING POSITION, WHEREIN ANY ONE OF SAID CLAMPS IS RELEASED FOR HINGED MOVEMENT BETWEEN ITS CLAMPING POSITION AND ITS RELEASING POSITION IN RESPONSE TO OPERATION OF THE ADJACENT COOPERATING ONE OF SAID FASTENING MECHANISMS FROM ITS HOLDING POSITION INTO ITS RELEASING POSITION, EACH ONE OF SAID END COVER SECTIONS CARRYING A DOWNWARDLY TURNED END FLANGE AND A PAIR OF DOWNWARDLY TURNED SIDE FLANGES THAT RESPECTIVELY EMBRACE THE CORRESPONDING ADJACENT PORTIONS OF THE END AND THE SIDES OF SAID RIM WHEN SAID ONE END COVER SECTION OCCUPIES ITS CLOSED POSITION, EACH ONE OF SAID INTERMEDIATE COVER SECTIONS CARRYING A PAIR OF DOWNWARDLY TURNED SIDE FLANGES THAT RESPECTIVELY EMBRACE THE CORRESPONDING ADJACENT PORTIONS OF THE SIDES OF SAID RIM WHEN SAID ONE INTERMEDIATE COVER SECTION OCCUPIES ITS CLOSED POSITION, EACH ONE OF SAID END COVER SECTIONS ALSO CARRYING A LATERALLY EXTENDING AND UPWARDLY DIRECTED END BOSS AT THE INNER END THEREOF, EACH ONE OF SAID INTERMEDIATE COVER SECTIONS ALSO CARRYING A PAIR OF LATERALLY EXTENDING AND UPWARDLY DIRECTED END BOSSES AT THE OPPOSITE ENDS THEREOF, WHEREBY TWO OF SAID END BOSSES ARE ARRANGED IN CONTIGUOUS POSITIONS WHEN THE TWO CORRESPONDING ADJACENT ONES OF SAID COVER SECTIONS OCCUPY THEIR CLOSED POSITIONS, AND EACH ONE OF SAID INTERMEDIATE CLAMPS HAVING A SUBSTANTIALLY CHANNEL-SHAPED CROSS SECTION AND PROVIDED WITH DOWNWARDLY DIRECTED FLANGES SO THAT WHEN SAID ONE INTERMEDIATE CLAMP OCCUPIES ITS CLAMPING POSITION IT EMBRACES AND COVERS THE ADJACENT AND CONTIGUOUS TWO OF SAID END BOSSES RESPECTIVELY CARRIED BY THE TWO CORRESPONDING ADJACENT ONES OF SAID COVER SECTIONS IN THEIR CLOSED POSITIONS.