_August 8._--Our morning drive brought us about breakfast time just outside the lines at Fort Lancaster. I learned that Captain Skillman had purchased a pair of mules here, and gone on in good condition. We have had a fine road, with abundance of good grazing, all the way from Fort Clarke to this post. Now that we have been a number of days on our journey, we find that many of our mules are becoming foot sore or tired; these are such as are new to the service, and they become, by the time the night drive is over, very much fatigued. Mules, with us, have to go through a period of hardening and a process of acclimation before they become adapted to the purposes of prairie staging. The speed at which we trot them, their hard work, the drinking of different kinds of water at different stopping places, all try the constitution of the animal, while even eating corn, which we feed to them at all times, whether on the road or at stations, is something to be learned. On the journey up from San Antonio to El Paso we change the limestone water of the coast for the water impregnated variously with vegetable matter, alkali, or sulphur. This change is found to affect men as well as all descriptions of stock, and mules often times give out when hard driven immediately after drinking either the waters of the Pecos or those of any of the watering places between that river and Fort Davis. Coming down the road from El Paso to San Antonio, reversing the course of this change, the water is not found to have the same effect. Took in a supply of corn, for which we paid $2 50 per bushel. Made 28 miles, camping on the Pecos at 8 p. m.