43. Where, by any permanent change in the dominant heritage, the burden on the servient heritage is materially increased and cannot be reduced by the servient owner without interfering with the lawful enjoyment of the easement, the easement is extinguished, unless- (a) it was intended for the beneficial enjoyment of the dominant heritage, to whatever extent the easement should be used; or (b) the injury caused to the servient owner by the change is so slight that no reasonable person would complain of it; or (c) the easement is an easement of necessity. Nothing in this section shall be deemed to apply to an easement entitling the dominant owner to support of the dominant heritage.