For which services, when performed, the said Albert C. Ramsey and Edward H. Carmick, contractors, are to be paid by the said United States the sum of four hundred and twenty-four thousand dollars a year, to wit: quarterly, in the months of May, August, November, and February, through the postmasters on the route, or otherwise, at the option of the Postmaster General of the United States; said pay to be subject, however, to be reduced or discontinued by the Postmaster General, as hereinafter stipulated, or to be suspended in case of delinquency. It is hereby stipulated and agreed by the said contractors and their sureties, that the Postmaster General may increase the service or change the schedule, he allowing a pro rata increase of compensation within the restrictions imposed by law for the additional service required; but the contractors may, in case of increased service or change of schedule, relinquish the contract, on timely notice, if they prefer it to the change. It is hereby also stipulated and agreed by the said contractors and their sureties, that in all cases there is to be a forfeiture of the pay of a trip when the trip is not performed, and of not more than three times the pay of a trip when the trip is not duly performed and no sufficient excuse for the failure is furnished; a forfeiture of at least one-fourth part of it when the running is so far behind time as to lose connexion with a depending mail, unless it is shown that the same was not caused by neglect, or want of proper skill or misconduct, and a forfeiture of a due proportion of it when a grade of service is rendered inferior to the mode of conveyance above stipulated; and that these forfeitures may be increased into penalties of a higher amount, according to the nature or frequency of the failure, and the importance of the mail; also that fines may be imposed upon the contractors, unless the delinquency be satisfactorily explained to the Postmaster General in due time, for failing to take from or deliver at a post office, or a steam-vessel, the mail, or any part of it; for suffering it to be wet, injured, lost, or destroyed; for carrying it in a place or manner that exposes it to depredation, loss or injury, by being wet, or otherwise; for refusing, after demand, to carry a mail by any vessel or other vehicle which the contractors run or are concerned in running on the route beyond the number of trips above specified; or for not arriving at the time set in the schedule, unless not caused by neglect or want of proper skill, or by misconduct. And for setting up or running an express to transmit letters or commercial intelligence in advance of the mail, or for transporting knowingly, or after being informed, any one engaged in transporting letters or mail matter in violation of the laws of the United States, a penalty of five hundred dollars may be exacted for each offence, and for each article so carried.