But these were far from being the only revolutionary elements. There followed in quick succession a new torpedo that ran with almost perfect accuracy for five or six miles and carried an explosive charge three or four times larger than anything previously known. It had seemed but yesterday that a mile was the torpedo’s almost outside range. Then, at the beginning of the decade of which I speak, the submarine had a low speed on the surface, and half of that below it, with a very limited area of manœuvre in which it could work. It seemed little more, many thought, than an ingenious toy capable, perhaps, of an occasional deadly surprise if an enemy’s fleet should come too near a harbour, but seemingly not destined to influence the grand tactics of war. But in an incredibly short time the submarine became a submersible ocean cruiser, with three times the radius of a pre-Dreadnought battleship, with a far higher surface speed, and able to carry guns of such power that they could sink a merchant ship with half-a-dozen rounds at four miles. In this, even the dullest could see something more than a change in naval tactics. Might not the whole nature of naval war be changed? For the long range torpedo that could be used in action, at a range equal to that at which the greatest guns could be expected to hit; the submarine that, completely hidden, could bring the torpedo to such short range that hits would be a certainty, the invisible boat that could evade the closest surface cordon and, almost undisturbed, hunt and destroy merchantmen on the trade routes--that, but for the submarine, would have been completely protected by the command won by the predominant fleet--wonderful as these new things were, they were far from exhausting the new developments of under-water war. Great ingenuity had been shown not only in developing very powerful mines, but in devising means of laying them by the fastest ships, so that not only could these deadly traps be set by merchantmen disguised as neutrals, but by fast cruisers whose speed could at any time enable them to evade the patrols. And, finally, it was equally obvious that the submarine could become a mine layer also. There was, then, literally no spot in the ocean that might not at any moment be mined.