For mines of copper, zinc, lead, and similar metals, it would be best to pursue a different plan, and simply provide by statute that such mines should be leased for short terms of years to the bidder who would offer to sell his product at the lowest price per ton at the mines, all lettings and relettings to be publicly advertised, and the successful bidder to give bonds for the faithful performance of his contract. It is difficult to see how, under these conditions, a combination to defeat competition could be formed. Relettings of expired leases would be frequent; and bidding by the _selling price_, a single competitor would be sufficient to break any combination. Of course the lease should specify a minimum product which the mine should furnish. It would be advisable, too, that a manifest duty of the government, which should be undertaken even under present conditions, should be observed. It should be required to work the mine with due attention to saving the greatest possible amount of ore or mineral contained in the seam or vein. The third class of monopolies, whose legal subjection to public control is acknowledged, are those connected with our municipal public works. There is already a widespread movement toward taking the control and operation of these out of the hands of private corporations, and placing it directly with the city government, and progress in this direction is very rapid. The author believes, however, that the general law already stated is applicable here. If the public works of States and of the nation are more economically and efficiently managed when in the hands of private parties, it is surely unwise, as a general rule, to entrust the operation of municipal works to the average city official. While it is in the highest degree desirable that water-works, gas, and electric-lighting plants, street railways, and the other municipal enterprises, discussed in Chapter V., should be _owned_ by the municipality, their operation, in cases where the employment of considerable labor and the carrying on of intricate business and mechanical operations is involved, should in general be entrusted to private companies. In every case where the financial condition of the municipality obliges it to rely at first upon private corporations for the construction and ownership of its public works, the franchise should expire at the end of a short term of years, and the city should then have the privilege of purchasing the works at their actual cost. As regards works for water supply, there can be little doubt that almost invariably the municipality should operate as well as own the works, for the administration of the works requires but a small amount of labor, and that of such a class that the city can safely carry it on. But gas or electric-light plants, both for street and resident lighting, should be operated by private companies.