We already have a margin in our favor in the gulf service, as our steamer, the “Texas,” has performed the duty in sixty hours; and the Pacific service has been done in twenty-four and thirty hours less than schedule time. Our recent reports from Mexico justify us in the expectation of carrying the mails in fourteen days from New Orleans to San Francisco, and six months of experimental operation will, I think, show the feasibility of doing the regular service in within fifteen days. In conclusion, I would add that we are exerting every energy in pushing the thing up, and shall spare neither time nor money in proving the truthfulness of all our positions. An estafette mail will be carried from Vera Cruz and New Orleans to San Francisco next month, until the service becomes regular. I am, with great respect, your obedient servant, ROBT. G. RANKIN, _President_. We have the _highest_ assurance of _our_ favorable position in Mexico. Hon. JAMES CAMPBELL, _Postmaster General U. S., &c._ * * * * * POST OFFICE DEPARTMENT, _July 9, 1853_. SIR: Your letter of the 15th ultimo came duly to hand. My attention having been specially called to the circumstances connected with the contemplated line to the Pacific via Vera Cruz and Acapulco, I feel it my duty, after due deliberation, to inform you that the conditional contract entered into between my predecessor, Mr. Hubbard, and Messrs. Ramsey and Carmick, for the conveyance of the mails over this line to San Francisco, does not meet with my approbation. In the first place, as at present advised, I consider the route impracticable for mail purposes. In the second place, the sums of money yearly drawn from the treasury for contracts, which have for several years been, and are still in force, for the transportation of the mails between the Atlantic and the Pacific, are very considerable, amounting to about $731,868. In view of this fact, and of the many sections and neighborhoods, in the different States, which are either greatly restricted in, or deprived altogether of mail facilities, it appears to me both inexpedient and unjust to go into the expenditure of a still further sum of $424,000 for the service in question.