Note 129 — Chapter XIII · ALKALI.

It will be interesting to compare with the above the following brief description of the Stassfurt salt deposits, taken from Ries’s Economic Geology of the United States, (1905), p. 127. “At the bottom is the main bed of rock salt which is broken up into layers 2-5 inches thick by layers of anhydrite. Above this come 200 feet of rock salt, with which are mixed layers of magnesium chloride and polyhalite.... Resting on this is 180 feet of rock salt, with alternating layers of sulphates chiefly kieserite, the sulphate of magnesia. These layers are about 1 foot thick. Lastly, and uppermost, is a 135-foot bed consisting of a series of reddish layers of rock salts of magnesia and potassium, kainite ... kieserite ... carnallite ... tachhydrite ... as well as masses of snow-white boracite.”