There was considerable excitement in California, during the latter part of December, about a supposed monopoly of flour. The article had been very scarce and high for some time, and the exorbitant rates it commanded were attributed in a great measure to an organized effort to force up prices. Indignation meetings were held in the interior, and in San Francisco several of the public prints endeavored to expose the supposed plots of the speculators. The timely arrival of cargoes from Chili and elsewhere, however, soon caused a decline, and the excitement on the subject consequently abated. Vallejo has been made the capital of the state. It possesses many advantages of situation, and promises to be a large city. If the government should continue to have its seat there, Vallejo may prove a formidable rival to San Francisco. At Sacramento city much alarm prevailed, in consequence of the rise of the water in the river and its tributaries. The papers say:-- The warm and unprecedented heavy rains of the last forty-eight hours have brought down upon us an avalanche of water from the snowy regions skirting the forks of the American River, and swollen the latter stream to a greater height than at any former period of the present season. At 9 o'clock, yesterday morning, the water was even with its natural banks, and soon after commenced percolating through the unfinished embankments at the gaps of the old levee. These were speedily torn away by the force of the current, and the water, now running on unobstructed through the breach of the new levee, and so on down towards the city. By dusk last evening, that portion of the town lying south of J and east of Fifth street, was entirely submerged, to the depth of from one to three feet. During the whole of yesterday the rain poured down in torrents, and the weather was warmer than we have known it for a month past. The American river continued to rise, up to a very late hour, and, at last accounts, was eleven and a half feet higher than on Wednesday. It is useless to deny the fact that the highest mark has not yet been reached, for there is a great body of snow that, under the influence of the present storm, must dissolve, and find its way to the Sacramento. The latter stream also rose steadily during Thursday, but still lacks some two feet of being up to the top of the levee. There is no danger whatever of the embankment yielding at any point in front of the city--the only danger to be apprehended is that it may not prove sufficiently high to retain the stream within its appropriate bounds. A small breach was discovered early yesterday morning in the new levee, near Dudley's farm, but it was repaired before any damage was done. There was a rumor prevailing last evening that Lisle's bridge had been swept away, but could be traced to no reliable source.