Mr. Bell goes on to say: “This lake suffered numerous and extensive variations of level during the Tertiary period. Some of the more recent horizons are still exposed at Pocatello, where on either side of the Portneuf estuary, in plain sight from the depot, well defined benches or terraces of shore-line gravel are left exposed one hundred feet above the town; and a succession of low step-terraces of lake-shore gravel, cut by the main track of the Oregon Short Line railroad between Pocatello and American Falls, plainly indicate the rapid recession of the lake levels of this period, and its final drainage and complete obliteration by the erosion of the Snake river channel to its present level. “Prior to the inception of the great floods of black lava that have filled the upper valley (near Pocatello), the shore lines and basin area of Lake Idaho were almost all composed of granite and Palaeozic formation. These formations were rich in placer and quartz gold.” It is thought that the Snake river deposits also contain some alloy of platinum or iridium. But gold is not the only valuable mineral deposit in Bannock county. Situated at the mouth of Sulphur canyon, five miles east of the town of Soda Springs, is a group of soda springs with associated deposits of native sulphur. These mines were worked in the late nineties and in the years 1901 and 1902 a considerable amount of sulphur was taken from them, but the enterprise was finally abandoned. The United States Geological Survey, in Bulletin 470, gives the following summary of these deposits: “The failure of an apparently well backed attempt to develop these deposits will render improbable any further attempts in the immediate future. It is extremely doubtful if the deposits can be profitably worked * * in competition with the relatively high-grade deposits of Wyoming and Utah.” The same bureau, in Part I of its publications for 1909, speaks more hopefully of the salt deposits in Bannock county. In an article on this subject, Carpel L. Breger says: “Valuable areas of salt-bearing land lie along the Wyoming-Idaho border in Bannock county, Idaho. In the old days, before the advent of railroads in the west, relatively large amounts of salt were boiled from the brine springs in this region and were hauled by ox team to supply Idaho and Montana mining camps. The emigrants to the northwest along the Lander route also drew upon this region for their salt. Indeed, some forty years ago, in the reports of the Hayden survey, this area was briefly described as containing the finest salt works west of the Mississippi. In those days as much as 200,000 pounds of salt was boiled per month, selling in the late sixties at $1.25 a hundred pounds at the springs.”