"Passing now to the eastern strip or portion, the slope of the Nevada, the heat, except in those deep cañons where the reverberation makes it sometimes even insupportable, is qualified in degree, according to the altitude. A gentle west wind, warmer in the lower parts or foothills by the heat of the valley, fans it all day. At points which are higher, the wind is cooler; but here also, on the slope of the Nevada, the nights are always cool in summer, so cool that the late and early frosts leave too short a space for the ordinary summer crop to mature, even where the altitude is not more than 3,000 or 4,000 feet. Meantime, at the top of the Sierra, where the west wind, piling up from below, breaks over into Utah, travelers undertake to say that in some of the passes it blows with such stress as even to polish the rocks, by the gravel and sand which it drives before it. The day is cloudless on the slope of the Sierra, as in the valley; but on the top there is now and then, or once in a year or two, a moderate thunder shower. With this exception, as referring to a part uninhabitable, thunder is scarcely ever heard in California. The principal thunders of California are underground. "We return now to the coast-wise mountain region, where the multiplicity and confusion of climates is most remarkable. Their variety we shall find depends on the courses of the wind currents, turned hither and thither by the mountains; partly also on the side any given place occupies of its valley or mountain; and partly on the proximity of the sea. Sprinkled in among these mountains, and more or less inclosed by them, are valleys, large and small, of the highest beauty. But a valley in California means something more than a scoop, or depression. It means a rich land-lake, leveled between the mountains, with a sharply defined, picturesque shore, where it meets the sides and runs into the indentations of the mountains. What is called the Bay of San Francisco, is a large salt water lake in the middle of a much larger land-lake, sometimes called the San Jose valley. It extends south of the city forty miles, and northward among islands and mountains, about twenty-five more, if we include what is called San Pueblo Bay. Three beautiful valleys of agricultural country, the Petaluma, Sonora, and Napa valleys, open into this larger valley of the bay, on the north end of it, between four mountain barriers, having each a short navigable creek or inlet. Still farther north is the Russian River valley, opening towards the sea, and the Clear Lake valley and region, which is the Switzerland of California. East of the San Jose valley, too, at the foot of Diabola, and up among the mountains, are the large Amador and San Ramon valleys, also the little gem of the Suñole. Now these valleys, which, if we except the great valley of the two rivers, comprise the plow-land of Middle California, have each a climate of its own, and productions that correspond.