'It may, however, be proper to notice a distinction between the case of a single principal and his agent, and that of several principals and their joint agent, which might otherwise cause some confusion. In both cases, as between the agent and a principal, the construction of the principal, whether he be a single principal, or one of several, is equally conclusive; but, in the latter case, both the principal and the agent bear a relation to the other principals, which must be taken into the estimate, in order to understand fully all the results which may grow out of the contest for power between them. Though the construction of the principal is conclusive against the joint agent, as between them, such is not the case between him and his associates. They both have an equal right of construction, and it would be the duty of the agent to bring the subject before the principal to be adjusted according to the terms of the instrument of association; and of the principal to submit to such adjustment. In such cases, the contract itself is the law, which must determine the relative rights and powers of the parties to it. The General Government is a case of joint agency,--the joint agent of the twenty-four sovereign States. It would be its duty, according to the principles established in such cases, instead of attempting to enforce its construction of its powers against that of the State, to bring the subject before the States themselves, in the only form in which, according to the provisions of the Constitution, it can be, by a proposition to amend, in the manner prescribed in the instrument, to be acted on by them in the only mode they can rightfully pursue, by expressly granting or withholding the contested power. Against this conclusion there can be raised but one objection, that the States have surrendered or transferred the right in question. If such be the fact, there ought to be no difficulty in establishing it.'