The dominant owner cannot, by merely altering or adding to the dominant heritage, substantially increase an easement.

Where an easement has been granted or bequeathed so that its extent shall be proportionate to the extent of the dominant heritage, if the dominant heritage is increased by alluvion, the easement is proportionately increased, and if the dominant heritage is diminished by dilluvion, the easement is proportionately diminished.

Save as aforesaid, no easement is affected by any change in the extent of the dominant or the servient heritage.

Illustrations

(a) A, the owner of a mill, has acquired a prescriptive right, to divert to his mill part of the water of a stream. A alters the machinery of his mill. He cannot therbey increase his right to divert water.

(b) A has acquired an easement to pollute a stream by carrying on a manufacture on its banks by which a certain quantity of foul matter is discharged into it. A extends his works and thereby increases the quantity discharged. He is responsible to the lower riparian owners for injury done by such increase.

(c) A, as the owner of a farm, has a right to take, for the purpose of manuring his farm, leaves which have fallen from the trees on B's land. A buys a field and unites it to his farm. A is not thereby entitled to take leaves to manure this field.