The necessity for this will be more, rather than less, apparent with the use of underground instead of overhead wires. The cost of placing wires in subways is far beyond the cost of stringing them on poles, and if we are obliged to build our subways large enough to accommodate all the rival wires which may be offered, we have a herculean task upon our hands. The great question of the monopoly of land can be merely touched in this connection. While the fact that land is natural wealth must be freely acknowledged, it is only where population is most dense that any great monopoly appears in its ownership. The principle is well established, indeed, that private ownership of land cannot stand in the way of the public good. When a railway is to be built, any man who refuses to sell right of way to the railway company at a reasonable price may have it judicially condemned and taken from him. We have already noted in the chapter on railway monopolies the injustice of permitting a single person or corporation to control and own any especially necessary means of communication, as a mountain pass or a long and expensive bridge, and the same principle is apparent in connection with the railway terminals in our large cities. The enormous expense attendant upon securing right of way for an entrance to the heart of the city, makes it a very difficult matter for any new company to obtain a terminus there, except by securing running rights over the tracks of an older company. To give to any single corporation the sole control of the entrance to a city _and permit it to charge what toll it pleases_ for trains that pass through it, evidently places the city at the mercy of a monopoly. Practically the case is not so bad as this, as most large cities have means of water communication, and the railroads are run to the heart of the city through the public streets. But the time is fast approaching when these city grade crossings will be done away with, and in every city of importance the railways will enter the city on elevated viaducts terminating in a single union depot. Evidently it is contrary to the public welfare to sink more capital in these expensive structures than is necessary; and in general, several companies will use a single structure for entrance and exit. It is evident that the control of these terminals, if vested in a single company, may give rise to just the abuse we have set forth; and that the city itself should retain enough control over its railway terminals and freight-transfer lines to ensure that no single carrier or combination shall monopolize them.