"There is an extensive ocean current of cold water, which coming from the northern regions of the Pacific, or, perhaps, from the Arctic, flows along the coast of California. It arrives charged with, and in its progress, emits air, which appears in the form of fog when It comes in contact with a higher temperature of the American coast, as the Gulf-stream of the Atlantic exhales vapor when it meets, in any part of its progress, a lower temperature. This current has not been surveyed, and, therefore, its source, temperature, velocity, width, and course, have not been accurately ascertained.
"It is believed by Lieut. Maury, on what he considers sufficient evidence—and no higher authority can be cited—that this current comes from the coasts of China and Japan, flows northwardly to the peninsula of Kamptschatka, and, making a circuit to the eastward, strikes the American coast in about latitude 41° or 42°. It passes thence, southwardly, and finally loses itself in the tropics.**
"As the summer advances in California, the moisture in the atmosphere and the earth, to a considerable depth, soon becomes exhausted; and the radiation of heat, from the extensive naked plains and hill-sides, is very great.
"The cold, dry currents of air from the north-east, after passing the Rocky Mountains and the Sierra Nevada, descend to the Pacific and absorb the moisture of the atmosphere to a great distance from the land. The cold air from the mountains, and that which accompanies the great ocean current from the north-west, thus become united, and vast banks of fog are generated, which, when driven by the wind, has a penetrating or cutting effect on the human skin, much more uncomfortable than would be felt in the humid atmosphere of the Atlantic at a much lower temperature.
"As the sun rises from day to day, week after week, and month after month, in unclouded brightness during the dry season, and pours down his unbroken rays on the dry, unprotected surface of the country, the heat becomes so much greater inland than it is on the ocean, that an under-current of cold air, bringing the fog with it, rushes over the coast-range of hills, and through their numerous passes, towards the interior.
"Every day as the heat, inland, attains a sufficient temperature, the cold, dry wind from the ocean commences to blow. This is usually from eleven to one o'clock; and as the day advances the wind increases and continues to blow till late at night. When the vacuum is filled, or the equilibrium of the atmosphere restored, the wind ceases: a perfect calm prevails until about the same hour the following day, when the process re-commences and progresses as before,
