the western terminus at Halsted street or east thereof; provided, however, that this company shall have the right from said city to construct said tunnel under any intervening street or streets and said river within said limits, but such location and construction shall be such as not to interfere with the capacity, usefulness or grade of said streets; said tunnel to be used by this company for street railroad tracks, and the construction thereof shall be commenced within three years and be completed within four years after the said City Council shall grant permission to said railroad company to make said improvements, unless prevented by injunctions or strikes, and the time said construction is so interfered with shall be added to said four years, all work to be done in a manner satisfactory to the Commissioner of Public Works, and the tracks through the tunnel shall be connected with the street railroad tracks controlled by this company. Now, therefore, be it ordained by the City Council: That the agreement in said resolution contained be and the same is hereby accepted by and on behalf of the city of Chicago as a consideration from said company for the passage and approval by the Mayor of the ordinances in said resolution specified, and authority is hereby granted said company to make the improvements therein mentioned."

When this ordinance was passed there was in force what is known as the Horse and Dummy Act, passed in 1874, which provided: "That any company which has been or shall be incorporated under the general laws of this State, for the purpose of constructing, maintaining or operating any horse or dummy railroad or tramway, may enter upon and appropriate any property necessary for the construction, maintenance and operation of its road, and all necessary siding, side tracks and appurtenances, and may, subject to the provisions contained in this act, locate and construct its road upon or over any street, alley, road or highway, or across or over any waters in this State, in such manner as not to unnecessarily obstruct the public use of such street, alley, road or highway, or interrupt the navigation of such waters."

In West Chicago Street R. R. Co. v. The People, 214 Illinois, 9, 19, the Supreme Court of Illinois, referring to this act, said: "This act was an addition to the charter of any company organized under the general incorporation act, and its provisions have existed under some form ever since, conferring powers, upon street railroad companies organized as the defendant is. It gave the defendant the right to construct its railroad either over or across the Chicago river, which included the tunnel, subject to the condition contained in it. Defendant could only hold real estate for the transaction of its business of maintaining and operating a street railroad, and the statute fixed the conditions under which it might use its real estate for building the tunnel."

The tunnel was completed by the railroad company in March, 1894, and has ever since been used and is now being used as a passageway under the river for its cars. When constructed (as well as at the present time) the water in the South Branch of the Chicago river over the tunnel near Van Buren street varied in depth from seventeen to eighteen and three-tenths feet.

On the third day of March, 1899, Congress passed a River and Harbor Act, among the provisions of which was one directing the Secretary of War to cause surveys to be made and the cost of improving certain rivers and harbors to be estimated and reported to Congress, as follows: "Improving Chicago river in Illinois: survey and estimate of cost for a channel twenty-one feet deep from its mouth to the stock yards, on the South Branch, and to Belmont avenue, on the North Branch so far as may be permitted by existing docks and wharves, exclusive of cost of removing or constructing bridges or piers or lowering tunnels; and the aforesaid depth of twenty-one feet is hereby adopted as the project depth for the improvement in lieu of that fixed by the act of June third, eighteen hundred and ninety-six; Provided, that all the work of removing and reconstructing bridges and piers and lowering tunnels necessary to permit a practicable channel with said depth to

be obtained shall be done, or caused to be done, by the city of Chicago, without expense to the United States." 30 Stat. 1121, 1156.

After the passage of that act steps were taken to dredge the Chicago river so as to deepen its channel in accordance with the provisions of the act of Congress, and, it is alleged, such work "has been proceeding under the authority and supervision of the Government of the United States, for the purpose of providing a sufficiently deep channel for the uses and purposes of commerce and navigation as aforesaid."

For the purpose of obeying the act of Congress, and in order to obtain a free and unobstructed navigation of the Chicago river for the benefit of commerce, interstate and domestic, the City Council of Chicago, on the nineteenth day of March, 1900, duly passed the following ordinance: "Whereas, by act of Congress of March 3, 1899, it is provided that in the survey and estimate of cost for a channel twenty-one feet deep, in the improvement of the Chicago river from its mouth to the stock yards on the South Branch, and to Belmont avenue on the North Branch, the aforesaid depth of twenty-one feet is adopted as the project depth for such improvement; whereas, it is in said act further provided that all the work of removing and reconstructing bridges and piers and lowering tunnels necessary to permit a practicable channel with said depth to be obtained, shall be done or caused to be done by the city of Chicago, without expense to the United States; whereas, the tunnel under the South Branch of the Chicago river at Van Buren street was constructed by the West Chicago Street Railroad Company under a certain ordinance of the city of Chicago, passed April 2, 1888; whereas, a channel in the Chicago river, of the depth of at least twenty-one feet is now made necessary by the requirements of navigation and by the increase in the draft of vessels engaged in the shipping trade of the Lakes; whereas, the said tunnel is an obstruction to said proposed improvement to the Chicago river and to the navigation thereof, and as such obstruction must be lowered so that there may be above it in

said river a depth of at least twenty-one feet of water, or be removed altogether: Now, therefore, be it ordained by the City Council of the city of Chicago: That the West Chicago Street Railroad Company be and it is hereby ordered and directed within three months after the date of the passage of this ordinance, at the sole cost and expense of said West Chicago Street Railroad Company and without cost, damage, loss or expense of any kind, whatsoever to the city of Chicago, to proceed to lower the tunnel under the South Branch of the Chicago river at or near Van Buren street, being the same tunnel heretofore constructed by the said West Chicago Street Railroad Company under an agreement dated April 2, 1888, between the said West Chicago Street Railroad Company and the city of Chicago, and an ordinance passed by the City Council of the city of Chicago, April 2, 1888, authorizing the construction of said tunnel in accordance with the provisions of said agreement, so as to provide for a clear depth above said tunnel of at least twenty-one feet of water at all times. Said work shall be performed by the said West Chicago Street Railroad Company under the supervision and direction and subject to the approval of the Commissioner of Public Works of the city of Chicago, and shall be completed on or before March 1, 1901."

In execution of the provisions of that ordinance the city caused notice to be given to the railroad company, demanding compliance with its provisions. The company did not heed that notice.

The present action was thereupon instituted by the people of Illinois, on the relation of the city of Chicago, against the railroad company. The specific relief asked was the issuing of a writ of mandamus directing the railroad company, without cost, damage, loss or expense of any kind whatsoever to the city, to proceed to lower its tunnel under the South Branch of the Chicago river at or near Van Buren street, so as to provide for a clear depth above it of at least twenty-one feet of water at all times, for its entire width and length, or to wholly remove it "so that the same shall cease to be an obstruction to the free

navigation of said Chicago river or the South Branch thereof, and to perform said work under the supervision and direction of the Commissioner of Public Works of the city of Chicago."

The Circuit Court found the issues for the defendant, and denied the application for a mandamus. Upon error to the Appellate Court, First District, the judgment of the Circuit Court was reversed and the cause remanded with directions "to issue a writ of mandamus commanding the railroad company to remove its tunnel, said writ not to be executed until the Washington street and La Salle street tunnels are both removed or lowered to a sufficient depth to be no longer an obstruction to navigation."

Upon appeal to the Supreme Court of Illinois a final judgment was there entered awarding a peremptory writ of mandamus as prayed for in the petition. West Chicago Street R. R. Co. v. People, 214 Illinois, 9.

As explanatory of the reference to the tunnels on Washington and La Salle streets it may be here stated that those tunnels belonged to the city, and were located between the tunnel at Van Buren street, owned by the railroad company, and the mouth of the river at the Lake. Of course, until the city's tunnels are lowered or removed, the lowering or removal of the tunnel on Van Buren street would not be of material aid to navigation.

We come now to consider the questions arising on the record and discussed at the bar.

1. The contention of the city that the writ of error should be dismissed for want of jurisdiction in this court cannot be sustained. It is true that the judgment of the state court rests partly upon grounds of local or general law. But, by its necessary operation-although the opinion of the state court does not expressly refer to the Constitution of the United Statesthe judgment rejects the claim of the company, specially set up in its answer, that the relief asked by the city cannot, in any view of the case, be granted consistently, either with the contract clause of the Constitution or with the clause prohibiting