estates. Windows which have been opened for twenty years or more, and enjoyed without molestation by the owner of the house. 2. It is proposed to consider, 1. How the right of ancient light is gained. 2, What amounts to interruption of an ancient light. 3, The remedy for obstructing an ancient light. 3. 1. How the right of opening or keeping a window open is gained. 1. By grant. 2. By lapse of time. Formerly it was holden that a party could not maintain an action for a nuisance to an ancient light, unless he had gained a right to the window by prescription. But the modern doctrine is, that upon proof of an adverse enjoyment of light; for twenty years or upwards, unexplained, a jury may be directed to presume a right by grant, or otherwise. But if the window was opened during the seisin of a mere tenant for life, or a tenancy for years, and the owner in fee did not acquiesce in, or know of, the use of the light, he would not be bound. If the owner of a close builds a house upon one half of it, with a window lighted from the other half, he cannot obstruct lights on the premises granted by him; and in such case no lapse of time necessary to confirm the grantee’s right to enjoy them. Where a building has been used twenty years to one purpose, (as a malt house,) and it is converted to another, (as a dwelling-house,) it is entitled in its new state only to the same degree of light which was necessary in its former state. It has been justly remarked, that the English doctrine as to ancient lights can hardly be regarded as applicable to narrow lots in the new and growing cities of this country; for the effect of the rule would be greatly to impair the value of vacant lots, or those having low buildings upon them, in the neighborhood of other buildings more than twenty years old.