La Paz is the seat of government and the principal port of Lower California, and its extensive bay affords excellent places of anchorage for vessels of any size, and is sufficiently commodious for the most numerous fleets. The principal pearl fisheries are in this immediate vicinity, and also the most valuable mining districts. It is the outlet of the fertile valley of the Todos Santos, and of the produce of the whole country between Santiago and Loreto. The cove or estero, opposite the town of La Paz, furnishes spacious and safe anchorage, which may be reached by vessels drawing not more than eighteen or twenty feet of water; and the cove of Pichilingue, at the south-eastern extremity of the bay, and about six miles from the town, affords an excellent anchorage for vessels of any size; but the inner bay can be reached only by small merchant vessels. The bar, however, between the two is only a few yards in extent; and if the importance of the place should ever justify it, the channel might be made deeper without difficulty or great expense. The adjacent country being barren and mountainous, and the roads to the interior exceedingly difficult, this place can never be the outlet of much agricultural produce. But as the island of Carmen, nearly opposite the entrance to this bay, contains an almost inexhaustible supply of salt, very easy of access, it is possible that the trade in this article may eventually give considerable importance to the port of Escondido. The bay of Mulige contains several places of anchorage, but none of them are deemed safe for large vessels, or even from small vessels, at all seasons of the year. There are also several other parts in the gulf farther north which are occasionally visited by coasting vessels, but it is not known that any of them are likely to be of much commercial importance. II. _Proposed system of defence._--It is not supposed that, under existing circumstances, any military post will be necessary on the western coast of the peninsula; nor is it probable that, for many years, any place there will become of sufficient importance to justify the construction of military works for its defence. It is true that the whale fishery on this coast has become, from the amount of shipping engaged in it, an object of the highest consideration; but our having ports of refuge at San Francisco or San Diego, and at La Paz, strong enough to resist a naval coup de main, will, it is believed, afford sufficient security to these whalers in case of a war with a maritime power.