If the United States possessed the power contended for under this grant, might they not in adopting the roads of the individual States for the carriage of the mail, as has been done, assume jurisdiction over them and preclude a right to interfere with or alter them? Might they not establish turnpikes and exercise all the other acts of sovereignty above stated over such roads necessary to protect them from injury and defray the expense of repairing them? Surely if the right exists these consequences necessarily followed as soon as the road was established. The absurdity of such a pretension must be apparent to all who examine it. In this way a large portion of the territory of every State might be taken from it, for there is scarcely a road in any State which will not be used for the transportation of the mail. A new field for legislation and internal government would thus be opened. From this view of the subject I think we may fairly conclude that the right to adopt and execute a system of internal improvement, or any part of it, has not been granted to Congress under the power to establish post-offices and post-roads; that the common roads of the country only were contemplated by that grant and are fully competent to all its purposes. The next object of inquiry is whether the right to declare war includes the right to adopt and execute this system of improvement. The objections to it are, I presume, not less conclusive than those which are applicable to the grant which we have just examined. Under the last-mentioned grant a claim has been set up to as much of that system as relates to roads. Under this it extends alike to roads and canals. We must examine this grant by the same rules of construction that were applied to the preceding one. The object was to take this power from the individual States and to vest it in the General Government. This has been done in clear and explicit terms, first by granting the power to Congress, and secondly by prohibiting the exercise of it by the States. "Congress shall have a right to declare war." This is the language of the grant. If the right to adopt and execute this system of improvement is included in it, it must be by way of incident only, since there is nothing in the grant itself which bears any relation to roads and canals. The following considerations, it is presumed, prove incontestably that this power has not been granted in that or any other manner.