With reference to the proposed boulevard link on Michigan Avenue, connecting the north and south sides, it is to be borne in mind that the city under its general powers can enlarge Michigan Avenue to any desired width and can alter the grade of the whole or any portion of the street. There were, however, passed by the legislature May 25, 1907, four acts which were designed to facilitate the construction of this boulevard link. It was in contemplation at that time that the South Park and Lincoln Park boards would do part of the work and defray part of the expense, and that the city would meet the balance of the cost by annual appropriations extending over a series of years. The first of these four acts[62] was designed to enable the South Park board to contribute such part of the expense as to it might seem best. This bill provides that the corporate authorities of any public park district having control of any park in a city wherein other park districts and parks are situated, but not connected therewith by any boulevard or driveway or other park thoroughfare, may from time to time in their discretion issue and sell additional bonds, not exceeding the five per cent limitation, in order to defray the expense of connecting any park under their control with any other public park or parks by means of a boulevard and driveway in the city, and altering and improving any connection or connections between such parks. Such bonds must, however, be authorized by the voters of the park district at an election. By the second act,[63] the Lincoln Park board is authorized to issue, upon a favorable vote of the electors of the district, bonds not exceeding $1,000,000 for the purpose of constructing surface and elevated boulevards and the approaches thereto over or along streets and alleys, when authorized to do so by any city having control thereof. The other two acts referred to were passed in order to dispel any doubt about the power of municipalities to erect an elevated structure in a public street. One[64] empowers any city to grant, by ordinance, to any board having jurisdiction over parks and boulevards the right to take and improve, by means of surface or elevated ways, a street not more than one mile in length, with all convenient or necessary approaches, inclines, and superstructures; while the other[65] confers power upon any city to construct and maintain an elevated way in any street, with all necessary approaches, inclines, and superstructures, and to authorize any commission or board having jurisdiction of a public park to take over, maintain, and control, upon terms fixed by ordinance, any street and any incline, approach, or superstructure therein.