The interest of the university school of mines in lignite experimentation did not end with the perfecting of the briquet process. The most recent achievement of the school is the production from lignite of activated carbon, a substance (hitherto produced largely from animal bones) used in water purification, sugar refining, rubber tire manufacture, and other commercial processes. The development of this product should furnish a new and profitable industry for western North Dakota. Western North Dakota has, in addition to its lignite beds, large deposits of clay. These, like lignite, engaged the interest of the late Dean E. J. Babcock of the university school of mines, and largely as a result of his efforts are being developed. Upon his urging, a ceramics department was created at the university in 1910 to determine the commercial value of native clays. From experiments conducted, it was found that certain varieties made excellent brick, tile, and other building materials, while others were especially suitable for pottery. Reproductions of fine European pottery and original pieces of local design turned out at the university have attracted attention at exhibitions throughout the United States. Large-scale commercial development of the State's clay deposits is centered at Dickinson, where both building materials and pottery are produced. Sodium sulphate and bentonite are two of the more recent mineral discoveries in North Dakota. In the southwestern part of the State are large beds of bentonite which, because close to the surface, are easily accessible for commercial purposes. Bentonite is used in the manufacture of paint, rubber, soap, cosmetics, dynamite, and a variety of other products; it has also been found to give rich gold and brown tones to decorative designs on pottery. The chalky-white crystals of sodium sulphate, sometimes known as Glauber's salts, are found in few places in the United States outside of the old lake beds of northwestern North Dakota. Sodium sulphate is principally used in the manufacture of paper. Millions of tons of it are easily accessible in the open lake beds where it has been deposited by springs. Development of mineral resources should help to solve the unemployment problem of the State--a problem which is constantly growing. Except in recent years, residents have had no difficulty in finding work, because agricultural pursuits usually require the same amount of labor year after year regardless of agricultural prices. Despite this, new factors are increasing unemployment. In the period between 1930 and 1935, North Dakota was the only State in the spring wheat belt to show an increase in population. Another primary cause of increasing unemployment is the steadily growing percentage of persons over 40 years of age: in 1900, 18.4 percent of the population was over 40, in 1920 this had increased to 20.8 percent, and in 1930 to 25.6 percent.