1. The enjoyment of apertures admitting light and air is an enjoyment 'as of right' when it is open and manifest, not furtive or invisible, and when it is not had in such wise as to involve the admission of an obstructive right in the owner of the alleged servient tenement. The phrase does not mean a right acquired through grant from the owner of the servient tenement, though the presumption of a grant from an enjoyment for twenty years was the basis of the English law on the subject. It may seem hard that the owner of a plot of land should be divested of one of the ordinary incidents of ownership by his neighbour's building a house on his land more than twenty years before the former wants to build, and that would be so if exclusive ownership were an ultimate fact; but the truth is, that both owners occupy under the sanction of the State, because such occupation is found conducive to the general welfare. The same principle warrants the use of land for purposes beneficial to community, and the protection of an enjoyment of apparent rights which has continued for a certain time, because men's arrangements naturally become fitted to a state of things which has thus continued, and in the great majority of cases such a period as twenty years affords ample opportunity for the assertion of a contradictory right by the servient owner. The Legislature, at any rate, has taken this view; and as there has, in this case, been an enjoyment of the lights openly, and without admission of any subsisting contradictory right, for twenty years, we must reverse the decree of the District Court, and restore that of the Subordinate Judge in this sense, that the defendant be enjoined against keeping up her roof in so far as it interferes with the accustomed access of light and air to the apertures in question with costs throughout on respondent.