and military marine in case of war with any naval power, will, it is believed, fully justify the expenditures necessary for securing this port against a maritime attack. III. _Commercial and military importance of Lower California._--Thus far in my report I have proceeded on the supposition that it is the intention of our government to retain the whole of California in any treaty of peace with Mexico; but doubts have recently been expressed on the policy of retaining this peninsula, on account of its being of little or no value to the United States. As the guerrilla forces which were sent over from Mexico the past summer, during the absence of our squadron from this coast, to regain possession of Lower California, and force the inhabitants to their allegiance to the Mexican government, have been defeated and completely dispersed, leaving our own troops in undisputed possession of the territory, nothing but a conviction of the utter worthlessness of the country could now induce our government to consent to its abandonment. On this subject I beg leave to add a few remarks: The peninsula of California lies between twenty-two degrees fifty minutes and thirty-two degrees thirty minutes north latitude, being about seven hundred miles in length, and varying from fifty to one hundred miles in breadth. An irregular chain or broken ridge of mountains extend from Cape St. Lucas to the frontiers of Upper California, with spurs running off on each side to the gulf and ocean. Between these spurs are numerous broad plains covered with stunted trees, and during the rainy months with a thin but nutricious grass. In the dry season this grass is parched up like hay, but from its nutricious character it affords abundant food for the herds of cattle and horses which constitute the principal wealth of rancheros. The dryness of the soil prevent the growth of trees of any considerable magnitude, except on the borders of a few mountain streams. This timber, though far from being plentiful, is exceedingly durable and much esteemed in ship-building. The greatest height of the mountains is estimated five thousand feet; many of them are piles of mere broken rocks, while others are covered with grass, shrubbery, and small trees. The plains are sandy and mostly unproductive--not, however, from any natural barrenness in the soil, but from a deficiency of water. There are but few durable streams in the whole country, and streams of good water are extremely scarce. But in the plains and most of the dry beds of rivers water can be obtained by digging wells only a few feet in depth; and wherever irrigation has been resorted to by means of these wells, the produce of the soil, from its remarkable fertility, has abundantly rewarded the labor of the agriculturist. Much of this soil is of volcanic origin, having been washed from the mountains by the action of heavy rains, and the produce extracted by means of irrigation from these apparently barren