War, whether it be _on_ the sea, _under_ the sea, on the land or in the air, is a science in which the human element is of at least equal importance with that of the purely mechanical. It is a science of both "blood and iron." The armed motor launches described in earlier pages, after being built in Canada to the number of over 500, and engined by the United States, were transported across the Atlantic on the decks of big ocean-going steamships--more than one of which was torpedoed on the voyage. On their arrival in Portsmouth dockyard the guns and depth charges were placed aboard and the vessels thoroughly equipped and fitted out for active service. Officers and men were drafted from the training establishments of the new navy at Southampton, Portsmouth, Chatham, Greenwich and elsewhere. Each little vessel was given a number, and within a few weeks of their arrival from the building yards on the St Lawrence they sailed in flotillas out past the fortifications of Spithead, _en route_ for their respective war bases. Great secrecy had surrounded the construction of these small but powerful craft, and but few naval men, except those directly engaged in the anti-submarine service, had either seen or heard much of them until they commenced arriving at the different rendezvous. Among the early flotillas to leave Portsmouth dockyard was one of four ships destined for a base on the east coast of Scotland, and as these speedy little craft raced away north the expectations of both officers and men ran high. It was in the early summer of 1916, and although the air was crisp, the sea sparkled in the bright sunlight and the sky was a cloudless blue. Only a heavy-beam sea off Flamborough Head had marred the maiden voyage, and they were now on the last hundred miles, with the low-lying Farne Islands fading into the mist astern. By nightfall, if the wind remained light, they would make the Scottish port which was to form their base of operations. Hitherto these four brand-new little warships, all white wood, grey paint and polished metal, had been plodding over the 600 miles of sea from Portsmouth at what was termed "cruising speed"--a mere 10 knots. The engines had not been opened out to "full ahead" because these delicate pieces of mechanism needed time to settle down to their work before it was safe to drive them to the utmost limit of speed and power, but now that pistons and bearings had been given time to "run in" it was considered safe for the flotilla to increase speed in order to make harbour by nightfall.