Sonora. (Measure on the map the land transportation to Tucson, respectively, from San Pedro, Cal., and from Guyamas.) I have made all the calculations herewith submitted with reference to passing through our own territory, without knowin the plands of the general or his authority in regard to Guymas, and merely hazard these suggestions in case Guaymas is to be held. Please get by telegraph this information from Washington, and sent it to me by mail, i. e., "from Colonel Canby's reports what is the strength of the rebels now in New Mexico and at Fort Bliss; what the description of the troops, and where are they stationed?" You will see by memorandum C the amount of forage, subsistence stores, &c., which must all be at Fort Yuma except 250,000 pounds of barley, before the troops cross the desert this side of the Colorado; because it will not to do concentrate the command at Fort Yuma until the supplies that they will consume after leaving there have been actually deposited at that point, and all risks of the river and accidents to the boat, &c., have been overcome. While this transportation is going on every preparation must be made here, so that the moment I am apprised that these supplies have reached Fort Yuma the march can be commenced. The quarters should employ at San Francisco strong, energetic Union men as teamsters. They should be armed with revolvers and the riflemen's knives now in the arsenal at Benicia. I have said nothing about a military chest for the expedition. Captain Kirkham will be able to tell the amount of ready money which should be taken along in the quartermaster's and commissary departments. The necessity of small coin should not be overlooked; for this purpose it can be specially prepared in the mint. For all purchases to be made in Sonora we must have specie. I shall send Surgeon McNulty to San Francisco, there to consult with the medical director as to what hospital stores, &c., are indispensably required, and none other. On is noted to send these stores by water to Fort Yuma. On consulation with Surgeon McNulty I find, to avoid accidents, they had better be shipped to San Pedro to go overland.

Please have purchased for the expedition by the commissary at San Francisco and shipped to Yuma two barrels unground black pepper. As the troops will carry no knapsacks, I wish to have straps prepared, so that each man can carry upon his back his blanket and great coat. In case the general approves of the latter suggestion, I have asked Lieutenant-Colonel West to have a pattern prepared while he is in San Francisco. I earnestly beg that the general will telegraph to Oregon and have the horses that were turned in there sent to San Pedro for the use of the First Cavalry. Those horses are accustomed to the noise of arms and to the saber exercise and in other respects are well trained. Some of them may be unfit for service, but eighty or ninety of the best I require. They are doubtless American stock and better capable for heavy men than the small California horses; besides, to supply this number from this neighborhood we should have just so many unbroken animals with which to commence a campaign. There should be twenty-five good pack mules in addition to those working in the train starting with aparejos and laden with forage. These will doubtless be required for expeditions to localities incaccessible to wagons. The aparejos are in the depot here and at Fort Yuma. I observed among the public wagons which came down on the Senator two metallic pontoon wagon beds. If you have more at Benicia, please have four additional ones sent down for the use of the expedition. There should be two coils lariat rope one-half inch in diameter come with these wagons; fifteen coils, say five-eighths inch in diameter, should be shipped to Yuma for