When one person becomes seized in fee of both the dominant and servient tenement, easements of light and all other easements are extinguished absolutely as regards those estates.

When one person becomes owner of dominant and servient tenements, for different estates in each, the easements are only suspended during unity of ownership and revive again on severance.

Easements may also be extinguished by release or abandonment by the dominant owner. A regular formal abandonment must be by deed, for a deed being necessary to create an easement by grant or covenant, so a deed is necessary to destroy one ; and just as the servient owner was the only person who could create an easement over his property by a deed or grant to the dominant owner, so a dominant owner is the only person who can extinguish an easement by a deed of regrant to the servient owner.

Similarly, as a grant may be implied under circumstances such as were referred to in the last chapter, so a regrant or release may sometimes be implied from circumstances. Non-use, coupled with other evidence of intention to abandon, may under some circumstances justify a conclusion that an easement has been abandoned, but mere non-use for some time will not ordinarily suffice to prove abandonment.

A class of case in which a doubt may often be raised whether an easement of light has been abandoned or not is where buildings with ancient lights have been demolished.

There can, of course, be no use or enjoyment when there is no building in existence, but the dominant owner may intend to rebuild, and to do this in such manner as to make beneficial use of the privilege of ancient lights which had been acquired for the demolished building. Sometimes he may set to work to build on the old site without any delay, and he may have all plans and designs for the new building ready in hand before the demolition of the old one ; and the architectural designs for the new buildings may clearly show that he distinctly intends to reopen windows in the new building in the same positions as the ancient lights of the old one.

In such a case there would be no room to doubt that the dominant owner wished and intended to preserve his easement, and, if anyone were to start building on the servient tenement in such fashion as to threaten to obstruct his ancient lights for the new building as designed, he might have a good cause of action for injunction.

Then there may be other cases where a building with ancient lights has been pulled down, but from one or other of many possible causes or from various causes combined no immediate or early rebuilding operations are commenced. In some such cases neighbours may be apparently justified in thinking that the ancient light rights have really been abandoned, and they may think themselves justified in building on their own land as though the ground on which the demolished building once stood were just a piece of ordinary vacant ground.

In some such cases there may be real grounds for doubt after some time whether the easement right is in existence or not, and the doubt can only be resolved by full and careful inquiry into all attendant circumstances which bear upon the question.

If it could be shown that the dominant owner had caused careful drawings or photographs of the old building to be prepared immediately or shortly before it was demolished, and marked the ancient lights on those drawings or photographs, or if there were other documentary evidence to show solicitude concerning the ancient lights, this kind of evidence might suffice to show that there was clearly no intention at the time of demolition to abandon the easement. Further, if there were any evidence of an intention at the time to erect new buildings with windows in positions corresponding to the ancient lights, there might be very satisfactory proof that there was a positive intention to preserve the privilege, and under such circumstances the privilege would survive ; but subsequent circumstances would have to be considered if there were any question of any subsequent abandonment. Speaking generally, the questions which arise in such cases are almost exclusively questions of fact to be tried and decided like any common jury case. The actual intention of the owner or occupier should commonly be inquired into when there is evidence of actual intention, but an intention to abandon may be presumed against him if he has acted in such manner as to induce the servient owner to believe that he would never resume the use and enjoyment of the casement, and more particularly if he were to stand by and allow a servient owner to expend a lot of money in building on an assumption that the easement was abandoned.

There are cases where, after a time, a man may be precluded from reasserting a right of easement unless he is reasonably vigilant and careful lest his conduct, considered in relation to that of his neighbour, may bring about a state of affairs where he may be estopped from setting up a claim.

It is here important to note that any question of abandonment can only arise after it is clearly established that an easement actually existed when the old building was pulled down.

Suppose, for example, that a building with windows which had been in existence for more than twenty years, but concerning which there had never been any suit or action, were pulled down, and suppose there had been no special privileges secured as easements by actual or implied grant, but that the owner had only his rights under the Prescription Act, then clearly, having only an inchoate right to an easement not yet complete, the demolition of the building would destroy the use, and after a year of non-use at latest the owner could not acquire an easement under the Prescription Act. It must not be forgotten by owners of household property that 50, 60, 70, or any other number of years of uninterrupted enjoyment of light through old windows will not alone suffice to create an easement, and that non-use or interruption, consented to or acquiesced in for one full year, will at any time suffice to destroy all claim for an easement under the Prescription Act.

When a house is pulled down the owner cannot use his old lights, and he may very soon lose all right to claim an easement for any new building which he may erect.