"A system of drainage, which would also secure irrigation, is absolutely necessary to give value to the great plain of the Sacramento and San Joaquin. This valley is so extensive and level that, if the rivers passing through it were never to overflow their banks, the rain which falls in winter would render the greater portion of it unfit for cultivation. The foundation of such a system can only be established in the survey and sale of the land. "_This can be done by laying out canals and drains, at suitable distances, and in proper directions, and by leaving wide margins to the rivers, that they may have plenty of room to increase their channels when their waters shall be confined within them by embankments._ "It would be well also to regulate the price of these lands, so as to meet, in some degree, the expense of draining them. "This system would, when agriculture shall become a pursuit in California, make this valley one of the most beautiful and productive portions of the Union." With regard to the present state of the commerce and of the commercial resources of California, it is observed, that her resources are confined almost entirely to the metallic wealth of the country, and that such a state of things would seem unfavorable to an extensive commercial intercourse. Undoubtedly, this metallic wealth of itself, could not long maintain an extensive commerce with the various nations of the earth. But when the _mineral_ wealth begins to be developed, as it soon will, there will be no lack of return freights for vessels arriving with supplies. The quicksilver mines already yield an enormous profit, and will soon be extensively worked. Respecting the present state of the commerce of the country, extent of her resources, and facilities of communication with the Atlantic States of the Union, and other countries, Mr. King's Report furnishes the following account-- "Gold is the product of the country, and is immediately available, in an uncoined state, for all the purposes of exchange. It is not there, as in other countries, where the productions of the earth and of art are sent to markets--foreign or domestic--to be exchanged for the precious metals, or other articles of value. There, gold not only supplies the medium of domestic trade, but of foreign commerce. "At first view, this state of things would seem to be unfavorable to an extensive intercourse with other parts of the world, because of the want of return freights of _home production_ for the vast number of vessels which will arrive with supplies. "These vessels, however, making no calculations on return cargoes, will estimate the entire profits of the voyage on their outward freights, and become, on their arrival, willing carriers for a comparatively small consideration. "This tendency in the course of trade, it would seem, must make San Francisco a warehouse for the supply, to a certain extent, of all the ports of the Pacific, American, Asiatic, and the Islands.