[I subsequently learned, and insert the facts here to make my report more connected, that these instructions reached Mr. Doyle on the 13th of July; the steamer for San Diego would sail on the 18th, thus leaving him only five days for making his preparations. Mr. Doyle agreed to take an interest, and to advance the money needed to commence service on the Pacific end of the line. The purchase and shipment of the necessary saddles, bridles, blankets, rations, arms, &c., as well as the selection of the first conductors and guard, was a work requiring more than five days. The first outfit, all but the animals, was shipped to San Diego on the 18th; the steamer arrived there on her usual time, namely, July 21st, leaving three days only in which to purchase the required animals. The difficulty in finding suitable mules proved greater than was anticipated, and the outfit, though nearly complete, could not be made ready to leave at 6 a. m. of the 24th, according to contract. The first mail for San Antonio left San Diego on the 9th of August; relays of animals having previously been sent forward to Fort Yuma.] _June 23._--From the 12th, the date of the signing of the contract, up to this date, I had been engaged in the necessary preliminary preparations for my journey to San Diego; also in making such purchases as I deemed indispensably necessary to be made in New York. My purchases in New York were limited, in comparison with the requirements of the line. I hardly knew myself what I wanted; therefore I determined to make the bulk of my purchases in San Antonio, where I hoped to get some reliable information as to my new duties. To-day Mr. Birch gave me my authority to act for him, which authority was made out in the form of a common letter, addressed by him to me, instead of a power of attorney. His purpose was to convey to me the most unlimited powers. I enclose a copy of this document. NEW YORK, _June 23, 1857_. DEAR SIR: I have taken a contract with the Postmaster General to carry the United States mail between San Diego and San Antonio twice a month for four years, a copy of which contract you have been furnished with. I wish you to take charge, for me, of the fulfilment of this contract, and of any additions that may be made to it, as my general agent for the purpose. After making all preliminary arrangements which you deem proper, I desire you to proceed to the line of the route, put it into operation, and perform the service. You are authorized by me to make all the contracts, and do all things you may deem necessary or proper for the purpose, having the same authority in the premises that I would myself if present. To carry out the above, I hand you certificates of deposit--