First National Bank v. Amarillo v. Amarillo National Bank, 531 S.W. 2d 905, 906-907 (Tex. 1975) (citations omitted).
“An easement appurtenant is an easement interest which attaches to the land and passes with it. An easement by implication is established when the owner of a single tract of land conveys any part and, although the deed is silent, the circumstances at the time of the conveyance are such as to cause an easement to arise between the two parcels of land thus created. Depending on whether the dominant estate is retained or conveyed, an implied easement may be reserved or granted. The law will read into the instrument of conveyance that which the circumstances show both the grantor and grantee must have intended had they given the obvious facts of the transaction proper consideration. In order to establish an implied grant of an easement appurtenant, the plaintiff must prove, along with other elements, that there was unity of title of the alleged dominant and servient estates.”
Des Moines & Southern Railway v. Am. Community Stores Corp., 131 N.W. 2d 515, 531 (Iowa 1964):
“A negative easement is defined in 28 C.J.S. Easements § 3d as a right in the owner of the dominant tenement to restrict the owner of the servient tenement, in respect of the tenement, in the exercise of the general and natural rights of property. In § 4 an easement appurtenant is defined as an incorporeal right which is attached to a superior right and inheres in the land to which it is attached. It is in the nature of a covenant running with the land. There must be a dominant and a servient tenement.”