Captain H. M. Naglee, seventh New York volunteers, with a strong detachment of his company, is now absent in pursuit of Indians in the valley of the San Joaquin. He has with him Lieutenant Burton's company of California volunteers, which is expected to return to Monterey before the end of this month; in which case I shall cause it to be mustered out of service, and discharged on the 31st day of October. Again I have to report the death, by sickness, of an officer of my command--Lieutenant C. C. Anderson, seventh New York volunteers, who contracted a fever when on duty at Fort Sacramento, and died in consequence at San Francisco on the 13th of September. He was buried with military honors by the troops at San Francisco, under direction of Major Hardie. This death reduces the number of officers in Captain Brackett's company, seventh regiment New York volunteers, to one captain and one second lieutenant. Commodore Shubrick will sail for the west coast of Mexico from this harbor next week; and having made application to me, I have directed Lieutenant Halleck, of the engineer corps, to accompany him, and shall give Lieutenant Colonel Burton, in command at La Paz, Lower California, authority to accompany Commodore Shubrick, should the latter design an attack upon any point or points of the west coast of Mexico, with orders, of course, to resume his position at La Paz as soon as the object is accomplished for which his command is desired. NOTE.--Colonel Burton will be directed to leave a sufficient number of men at La Paz to keep the flag flying. It affords me much pleasure to assure the department that the most perfect harmony subsists between the members of the naval and land forces on this coast, and that the most friendly intercourse is kept up between the officers. I have had frequent occasion myself to ask assistance of Commodores Biddle and Shubrick, and my requests have been granted with promptness and politeness; and in return I have afforded them all the assistance in my power. Our consultations have been frequent and perfectly harmonious, resulting, I hope, in the advancement of the common cause of our country. I have the honor to be, your most obedient servant, R. B. MASON, _Colonel 1st Dragoons, Commanding_. To General R. Jones, _Adjutant-General, Washington, D.C._ APPENDIX J. We have already given the substance of Governor Mason's despatch to the government, giving an account of the gold discovery and a visit to the _placers_. There is, therefore, no necessity for inserting that official document. The appearance in Upper California, in July 1848, of Don Pio Pico, the former governor of the territory, gave rise to serious apprehensions of another insurrection. The despatch of Col. Stephenson, the commander of the garrison at Los Angeles, to Colonel Mason, contains an account of the matter, together with a description of the ex-governor.