These ships have become notorious for breaking all flying records for non-rigid airships. Even the first ship of the class, despite the unsatisfactory power units, so long ago as in the summer of 1917 completed a flight of 49 hours 22 minutes, which at the time was the record flight of any British airship. Since that date numerous flights of quite unprecedented duration have been achieved, one of 61 1/2 hours being particularly noteworthy, and those of upwards of 30 hours have become quite commonplace. Since the Armistice one of these ships completed the unparalleled total of 101 hours, which at that date was the world's record flight, and afforded considerable evidence as to the utility of the non-rigid type for overseas patrol, and even opens up the possibility of employing ships of similar or slightly greater dimensions for commercial purposes. N.S. 6 appeared several times over London in the summer months of 1918, and one could not help being struck by the ease with which she was steered and her power to remain almost stationary over such a small area as Trafalgar Square for a quite considerable period. The flights referred to above were not in any way stunt performances to pile up a handsome aggregate of hours, but were the ordinary flying routine of the station to which the ships were attached, and most of the hours were spent in escorting convoys and hunting for submarines. In addition to these duties, manoeuvres were carried out on occasions with the Fleet or units thereof. From the foregoing observations it must be manifest that this type of ship, in its present modified state, is a signal success, and is probably the best large non-rigid airship that has been produced in any country. For the purposes of comparison it will be interesting to tabulate the performances of the standard types of non-rigid airships. The leading dimensions are also included in this summary: Type S.S. Zero S.S. Twin Coastal North Star Sea Length 143' 0" 165' 0" 218' 0" 262' 0" Overall width 32' 0" 35' 6" 49' 3" 56' 9" Overall height 46' 0" 49' 0" 57' 6" 69' 3" Hydrogen capacity (cubic feet) 70,000 100,000 210,000 360,000 Gross lift (lb.) 4,900 7,000 14,500 24,300 Disposable lift (lb.) 1,850 2,200 4,850 8,500 Crew 3 4 5 10 Lift available for fuel and freight (lb.) 1,370 1,540 4,050 6,900 Petrol consumption at full speed (lb. per hour) 3.6 7.2 18.4 29.8 Gals. per hour 0.36 0.72 2.05 3 CHAPTER VII NAVAL AIRSHIPS.--THE RIGIDS--RIGID AIRSHIP No. 1