_Franchises._—A still more noticeable monopoly is granted by municipalities under what is called a franchise for the establishment and maintenance of water supply, public means of artificial lighting and heating, or means of public transportation. These are under government control usually in cities, because they employ the public streets for carrying on the enterprise. The franchise is really an extension of the license in particular directions. This is usually issued with the expectation of great public benefit from a large investment of capital which would not be made without relief from competition, because not immediately profitable. The franchise usually carries with it certain restrictions as to use of public highways and limitation to a term of years. It necessarily involves the right of government inspection and control for the general welfare. _Difficulties from monopoly privileges._—All of these monopolies are granted for the purpose of conferring upon the whole community benefits that could not otherwise be secured. They are wise only so far as they secure this result. If the patent right system wastes the energies of inventors in contrivance of useless devices, there is loss; if it builds up a class of mere speculators, there is waste; if it fosters monopoly beyond the giving of a fair reward for invention, it is robbery. The exact limit of time during which a patent is good stimulates to the utmost exertion for wide introduction of its benefits, and at the same time prevents the burden of lasting monopoly. The dangers are chiefly in the administration of patent laws, from the careless issue of undeserved patents, or in a combination under a series of patents to maintain a constant monopoly. It is a safe rule to issue patents only for particular applications of scientific principles and not for the discovery of the principle, which can be protected in publication by copyright. Departures from this rule cut off the possibility of more perfect contrivances and fair competition in devices and methods. There can be no question of the general advantage of protecting a genuine inventor from the trespass of others to secure him a fair compensation. No other plan for a fair exchange of such services has even been suggested. The unsettled question is the proper limit of time for a patent to run.