15. Where the access and use of light or air to and for any building have been peaceably enjoyed therewith, as an easement, without interruption, and for twenty years, and where support from one person's land or things affixed thereto has been peaceably received by another person's land subjected to artificial pressure or by things affixed thereto, as an easement, without interruption, and for twenty years, and where a right of way or any other easement has been peaceably and openly enjoyed by any person claiming title thereto, as an easement, and as of right, without interruption, and for twenty years, the right to such access and use of light or air, support or other easement shall be absolute. Each of the said periods of twenty years shall be taken to be a period ending within two years next before the institution of the suit wherein the claim to which such period relates is contested. Explanation I.-Nothing is an enjoyment within the meaning of this section when it has been had in pursuance of an agreement with the owner or occupier of the property over which the right is claimed, and it is apparent from the agreement that such right has not been granted as an easement, or, if granted as an easement, that it has been granted for a limited period, or subject to a condition on the fulfilment of which it is to cease. Explanation II.-Nothing is an interruption within the meaning of this section unless where there is an actual cessation of the enjoyment by reason of an obstruction by the act of some person other than the claimant, and unless such obstruction is submitted to or acquiesced in for one year after the claimant has notice thereof and of the person making or authorizing the same to be made. Explanation III.-Suspension of enjoyment in pursuance of a contract between the dominant and servient owners is not an interruption within meaning of this section. Explanation IV.-In the case of an easement to pollute water, the said period of twenty years begins when the pollution first prejudices perceptibly the servient heritage. When the property over which a right is claimed under this section belongs to the Government, this section shall be read as if, for the words “twenty years” the words “sixty years” were substituted. Illustrations (a) A suit is brought in 1883 for obstructing a right of way. The defendant admits the obstruction, but denies the right of way. The plaintiff proves that the right was peaceably and openly enjoyed by him, claiming title thereto as an easement and as of right, without interruption, from 1st January, 1862, to 1st January, 1882. The plaintiff is entitled to judgment. (b) In a like suit the plaintiff shows that the right was peaceably and openly enjoyed by him for twenty years. The defendant proves that for a year of that time the plaintiff was entitled to possession of the servient heritage as lessee thereof and enjoyed the right as such lessee. The suit shall be dismissed, for the right of way has not been enjoyed “as an easement” for twenty years. (c) In a like suit the plaintiff shows that the right was peaceably and openly enjoyed by him for twenty years. The defendant proves that the plaintiff on one occasion during the twenty years had admitted that the user was not of right and asked his leave to enjoy the right. The suit shall be dismissed, for the right of way has not been enjoyed “as of right” for twenty years.