HEADQUARTERS SOUTHERN MILITARY DISTRICT, _Los Angeles, California, July 20, 1848_. SIR: By the last mail I informed you of the arrival of Don Pio Pico in this district. I subsequently learned that he had passed through San Diego without presenting himself to Captain Shannon, or in any manner reporting his arrival. Immediately after his arrival, rumors reached me of conversations had by him with his countrymen, in which he stated that he had returned with full powers to resume his gubernatorial functions, and that he had only to exhibit his credentials to you to have the civil government turned over to him. I found the people becoming very much excited, and some rather disposed to be imprudent. I sent for Jose Ant. Carrillo and some others in the town, who were giving currency to these reports, and informed them that I should hold them responsible for any imprudent or indiscreet act of their countrymen, and that, at the first appearance of any disrespect to the American authorities, I should arrest and confine them in the guard-house. This had the effect to check all excitement here; but as Don Pio removed up the country, the same excitement began to spread among the rancheros. In the mean time, his brother Andreas informed me that he, Don Pio, would come in and report to me in person in a few days, as soon as he had recovered from the fatigue of his journey. On Saturday, the 15th instant, he reached the ranch of an Englishman named Workman, some eighteen miles from here. This man has ever been hostile to the American cause and interest, and is just the man to advise Pico not to come in and report to me.