The illustrations used in the preceding paragraph have all related to the taking of land; but there is nothing in the constitutional provisions on the subject which would limit the power of eminent domain to the taking of real property. No doubt personal property might be taken under the same restrictions, but the necessity for taking or authorizing the taking of personal property will seldom arise, since in most cases the personal property of one owner will be no more essential than that of another owner; and such property, as far as needed, can be secured by purchase from some owner willing to sell for a reasonable price, and the necessity for condemnation of the property of an unwilling owner will not arise. But in reference to real property which is of such peculiar nature that different parcels or portions thereof cannot be regarded as necessarily interchangeable or capable of substitution, there may still be a question as to the nature of the interest therein or the extent of the use thereof which may be appropriated.

For some purposes the entire, permanent, and exclusive ownership may be necessary and the fee title may be taken, compensation on the basis of the entire value of the property being required to be made. Thus if a state or a city were condemning land to be used as the site of a public building, the state or city would necessarily acquire the complete ownership of the land taken and must pay damages accordingly; but for public highways, and for the right of way for railways, the use and occupancy of the surface is all that is essential, and it may properly be provided that such use only shall be condemned, and compensation for such use paid, leaving in the original owner of the land the right to any beneficial enjoyment of it and especially of coal or mineral rights under it which he may be able to make without interfering with the easement, as it is called, which is taken over the land for public purposes. The city may be authorized in condemning land for streets to take either the fee or an easement as the legislature in its discretion may provide.

The distinction between the taking of the fee and of an easement becomes important in considering the use which may be subsequently made of the right condemned. Thus where an easement over lands is condemned for use as a highway, leaving the title in the owner for every purpose not inconsistent with the public use for highway purposes, a railway company cannot be authorized, without payment of additional compensation, to locate its track and operate its road in such highway, because this is a further infringement on the rights of the property owner for which he has not received compensation; inasmuch as his compensation when the highway was located was determined with reference to the use of his property as a highway, and not for some other public purpose. Likewise, it might well be urged that telegraph or telephone lines could not be established along such highways without additional compensation to the property owner (Pierce v. Drew). The use involved in the establishment of city streets over private property is a more extensive use than that involved in the establishment of an ordinary highway, and may well be considered as including the construction and operation of telegraph and telephone lines, street railways, grading, curbing, paving, sewering, and other forms of improvements usually incident to the public enjoyment of city streets. The nature and extent of the right acquired by condemnation will depend largely upon the statutory provisions under which condemnation has been made.

As a general rule, the appropriation of land to one public use precludes its subsequent appropriation to another and inconsistent public use. When the state has condemned land for its use in "connection with public buildings, either as furnishing the site therefor or the necessary surrounding grounds, the same land cannot be taken a second time by a city for a park, or by a school district for school purposes. Such matters are, after all, in the discretion of the legislative power (U. S. v. Gettysburg Electric R. Co.). A limitation of more practical importance is that a railway company, having the general authority to condemn land for right of way, cannot without direct legislative sanction exercise the power of eminent domain for the purpose of acquiring a right of way over land already appropriated for public use under the authority of the state. For this reason one railway company cannot, under its general power to condemn, take the right of way of another railway company, and yet the legislature has the authority to provide for one railway crossing the right of way of another, or that when any one railway has abandoned the use of its right of way, it may be condemned for the use of another.

As between the federal government and a state government, neither one can authorize the condemnation for public use of land which has already been acquired either by condemnation or purchase by the other for its public uses. Possibly the United States government could not, by any action of the state, be excluded from appropriating state property for federal purposes; but such questions are not likely to arise, for it is hardly conceivable that the federal government should find it expedient and necessary to interfere with any state in the enjoyment and discharge of its public rights and duties.

An individual or corporation which has under proper authority condemned land for public uses, though for private benefit, has a property right in the land thus acquired; but this private right is still subject to be taken for other public uses if the legislature shall so provide. Thus a company which has constructed a toll bridge across a stream and has acquired necessary land for that purpose, has a property right in maintaining such toll bridge, and deriving the profits incident thereto; but under legislative authority, such property might be taken for the construction of a public bridge, due compensation being made to the company (CentralBridge Corp. v. Lowell). Public corporations, however, do not have a vested right which the legislature may not take away without making compensation to them, for all their rights and privileges are derived from and subject to the control of the legislative power. Questions of this kind arise more frequently under the constitutional provision as to impairing the obligation of a contract, and the extent to which corporate franchises either public or private may be impaired by legislation will be discussed elsewhere. (See below, § 269.)