The great difficulty in applying such a tax lies in the methods of reaching an understanding on the value of the franchise. How can this indefinite something be made visible on the tax books? In many instances the franchise may be regarded as inseparable from the real property of the corporation. The rails of a tramway, the poles and wires of a telegraph company, the pipes and conduits of a gas company, are real and tangible things, necessary to a proper conduct to the respective functions of the corporations. But the right to lay tracks in the public streets, to sink pipes under the streets, or to string wires overhead is as necessary a possession and as essential to the performance of what the corporation was created to accomplish. Whether this permits the franchise to be regarded as "real estate" and so offers it for taxation is a question of some theoretical interest, but of little practical importance.[16] Unless the franchise is regarded in this way, as belonging to real estate, or as forming a taxable entity apart from other property, it would be simpler to reach it through a corporation tax in one of the many ways open for applying that tax. [Footnote 16: A recent law of New York is very full on this point: "The terms 'land,' 'real estate,' and 'real property,' as used in this chapter, include the land itself above and under the water, all buildings and other articles and structures, substructures, and superstructures, erected upon, under, or above, or affixed to the same; all wharves and piers, including the value of the right to collect wharfage, cranage, or dockage thereon; all bridges, all telegraph lines, wires, poles, and appurtenances; all supports and inclosures for electrical conductors and other appurtenances upon, above, and underground; all surface, underground, or elevated railroads, including the value of all franchises, rights or permission to construct, maintain, or operate the same in, under, above, on, or through streets, highways, or public places; all railroad structures, substructures, and superstructures, tracks, and the iron thereon, branches, switches, and other fixtures permitted or authorized to be made, laid, or placed on, upon, above, or under any public or private road, street, or grounds; all mains, pipes, and tanks laid or placed in, upon, above, or under any public or private street or place for conducting steam, heat, water, oil, electricity, or any property, substance, or product capable of transportation or conveyance therein, or that is protected thereby, including the value of all franchises, rights, authority, or permission to construct, maintain, or operate in, under, above, upon, or through any streets, highways, or public places, any mains, pipes, tanks, conduits, or wires, with their appurtenances, for conducting water, steam, heat, light, power,