We have seen that the functions of co-operation with the Navy--Coast defence and Fleet assistance--were very complicated, and that at the outbreak of war the splendid pilots and excellent equipment of the R.N.A.S. were not so highly organized and were wanting in cohesion, but that the R.N.A.S. had advanced further than the Royal Flying Corps in specialized technical development. In the earlier part of the war, in addition to its main duties, the R.N.A.S. ventured in many directions, many of them of considerable value to the Army, as, for instance, at Antwerp. _Coast Defence, Patrol and Convoy Work._ Immediately war broke out a system of coastal patrols was established between the Humber and the Thames Estuary and over the Channel--the latter serving as an escort to the Expeditionary Force crossing to France. Patrols were at first, through limitations of equipment, mainly confined to the Home coast, but, as the war went on and machines improved, they were rapidly extended, especially in connection with the detection and destruction of submarines; reconnaissances were carried out over the enemy's shores, and in 1918 there were forty-three flights of seaplanes, thirty flights of aeroplanes, together with flying boats and airships, operating from, and communicating with, an ever-increasing number of shore stations. Not only was anti-submarine work carried out in the vicinity of the coast, but organized hunts were made for submarines, ships were convoyed on the high seas, shipping routes were protected, and action was taken to bar the passage of submarines through narrow channels. This was effected by an intensive system of combining and interlocking patrols, and by maintaining, in close co-operation with surface craft, a protective barrage across suitable stretches of water, such as the Straits of Dover. Airships from the beginning, when patrols operated from Kingsnorth during the crossing of the Expeditionary Force to France, proved particularly useful for escort, in addition to patrol work, and twenty-seven small airships, known as the S.S. type, were completed in 1915. In 1916 the Coastal type with a longer range was designed and constructed and new airship bases were established. _Fleet Assistance, Reconnaissance, Spotting for Ships' Guns._