The day of Wednesday, April 3, was spent in crossing the low hills east of Concord and in traveling along the southern shore of Suisun Bay as far as Antioch Bridge. Neither Anza nor Font has particular comment concerning the one and one-half leagues, which brought them to the summit of Willow Pass, overlooking the area of Pittsburg. Beyond this point the explorers entered the northwest corner of the San Joaquin Valley, or the western tip of the delta. They probably had just left Costanoan territory, although, to be sure, the exact tribal boundaries are unknown. At any rate it is preferable to limit the present discussion to the region west and south of the low hills which extend from Port Chicago southeast to the vicinity of Byron. The rancherias which were seen near Antioch would therefore be more profitably considered in a survey of the valley tribes than in one of the East Bay and adjacent coast ranges. Thursday, April 4, was spent in the famous attempt to cross the great tule swamps. In the course of this effort the party bore southeastward along the margin of the tules as far as the latitude of Bethany (Bolton, 1930, III: 148n). Thence they turned inland over Patterson Pass and, if Bolton's reconstruction is correct, followed up the ridge to the east of Arroyo Mocho. No trees or water were encountered until a point was reached not far southeast of Livermore. In the meantime, no Indians were seen and no traces of villages observed along the line of march. The journey of Friday, April 5, took the party into the rough country due east of Mt. Hamilton as far as the southeastern edge of San Antonio Valley at the head of the east fork of Coyote Creek. The terrain was extremely hilly and was covered with oak and coniferous trees, probably principally digger pine, although Font says he saw "spruce." Great stretches of chamise (_Adenostema fasciculatum_), which Anza calls "Mattal," were observed. The descriptions make it clear that the type of vegetation and the general appearance of the country were essentially as they are today. Only a few streams are mentioned: Arroyo Mocho is described merely as an "arroyo in a canyon." There were several small watercourses near the upper end of San Antonio Valley, and water in pools was found at the lower end near the night's camp. These streams may have been Sulphur Spring Creek and San Antonio Creek. The area was destitute of natives. The only mention of Indians is by Font (F2, p. 414). In the course of the valley [San Antonio Valley] we saw some ruinous and abandoned little huts, but the only Indian seen was at a distance and running, for as soon as he saw us he fled for the brush of the Sierra like a deer.