The most telling of these trials were against Widgeon, which was not only the fastest of the mail packets, but also the closest ship in size and horsepower to Archimedes. Widgeon proved to be slightly faster than Archimedes in smooth seas, but Chappell concluded that as the latter had a lower horsepower-to-weight ratio, the screw propeller as a means of propulsion had proven "equal, if not superior, to that of the ordinary paddle-wheel."[22] This finding was more decisive than it may appear, because from a naval perspective, screw propulsion had only to prove itself approximately equal in efficiency to paddlewheel propulsion, as paddlewheels had well recognized shortcomings in military use. These included the exposure of the paddlewheel and its engines to enemy fire, as well as the reduction of space available for the placement of cannon which impinged upon a warship's broadside firepower.