After the deposition of the borax bed a general subsidence of the region occurred, the waters of the great Tertiary lake once more covering the whole country. Again the sands and finer sedimentary material—the erosion of the mountains—were carried down and found a resting place on the floor of the lake, the borax bed being finally covered with several hundred feet of this detritus. Now, as the same formation in which the borax mine is found, and even the lower members of the rocks of that age, are seen resting upon the high ridges and on some of the peaks of the Calico hills, it would seem highly improbable, to say the least, that these sediments were built up from the ruins of the Calico Mountains themselves, but their source was in more distant ranges. Besides the regular vein-like deposit of calcium borate found at the borax mine, there are numerous small veinlets in other parts of the district in which calcium borate and gypsum are found filling cracks and cavities, probably as the result of infiltration. So common are these small fissures and beds of borax and gypsum that that portion of the sedimentary strata lying east of the town of Calico is usually spoken of as the borax formation by the miners of the district. To thoroughly investigate all the phenomena connected with these wonderful deposits and their mode of formation would require more time than was at my disposal. As has been previously stated, remnants of the sediments are still found lying high up on the flanks of the mountains, and even far into the interior of the hills, and there is every probability that the entire region included in the Calico District, as well as the country for many miles around, was at one time buried a thousand feet beneath these stratified rocks. With the uplift, the strata inclosing the borax mine were tilted and folded, and now the sheet of white calcium borate which once lay glistening in the sun on the bed of a desert dry lake stands like a great vein traversing the country. There are apparently two of these veins in close proximity to each other, but I believe them to be one and the same, being repeated as the result of an anticlinal fold. An ideal cross-section of the borax mine is here given (p. 347), showing the nature of the folding at that point; it is not drawn to a scale, being a sketch only. To the southward of the mine is seen a large mass of liparite, which has been pushed up from below. I had not the time necessary to trace out the line of fracture, but I am of the opinion that it occurs on the line of the great fault shown on the map of the fault system of the region.