So a return to the breech-loading ordnance became inevitable, and the change was made. The old Armstrong moveable vent-piece was avoided, however, in the new designs; of the two alternative breech-closing systems in use, viz. the wedge system of Krupp and the “interrupted screw” system of the French, the latter was adopted. A steel tube, rifled on the polygroove system, formed the body of the piece, and this was strengthened by hoops of iron or steel shrunk on its exterior. The new gun yielded a very great increase of power. Muzzle-loading guns were at once displaced, in the projected programme of new battleships, for the new type of ordnance, and a further series of revolutionary changes in ship armament at once took place. Other nations had already augmented the length and power of their guns. By the adoption of the improved breech-loading ordnance, Great Britain, who for the last few years had been falling behind her rivals, not only drew level with them but definitely took the lead in the power of her heavy ordnance: a lead which from that time to this she has successfully maintained. CHAPTER IX PROPELLING MACHINERY No aspect of old naval warfare is so difficult for the modern reader to visualize, perhaps, as that which displays the essential weakness of the sailing warship: its impotence in a calm. It was a creature requiring for its activities two elements, air and water. Ruffle the sea with a breeze, and the sailing ship had power of motion towards most of the points of the compass; withdraw the winds, and she lay glued to the smooth water or rolling dangerously in the heavy swell, without power either of turning or translation. For centuries this weakness told heavily against her and in favour of the oar-propelled vessel, particularly in certain latitudes. Through many years, indeed, the two types held ascendancy each in its own waters; in the smooth stretches of the Mediterranean the oar-driven galley, light, swift, and using its sharp ram or bow-cannon as chief means of offence or defence, was a deadly danger to the becalmed sailing ship; in the rougher north Atlantic the sailing ship, strong, heavy, capacious, and armed for attack and defence only along its sides, proved far too fast and powerful for the oar-driven rival. Progress--increase of size, improvement in artillery, the development of the science of navigation--favoured the sailing ship, so that there came at last the day when, even in the Mediterranean, she attained ascendancy over the galley. But always there was this inherent weakness: in a dead calm the sailing ship lay open to attack from a quarter where her defence lay bare. Ninety-nine times out of a hundred, perhaps, she could move sufficiently to beat off her attacker by bringing her broadsides to bear. The hundredth, she lay at the mercy of her adversary, who could, by choosing his range and quarter of attack, make her temporary inferiority the occasion of defeat. For this military reason many