=Oil and Gas.= Although prospecting had been done in earlier years, the real development of oil and gas in Kansas began about 1892, with the discovery of the big Kansas-Oklahoma field. The oil and gas area is included within an irregular strip, forty to fifty miles wide, extending from Kansas City southwesterly into Oklahoma. It is frequently spoken of as the “oil and gas belt.” By 1900 nearly every town in the gas belt had more gas than it knew what to do with, and various manufacturing enterprises, such as brick plants, zinc smelters, glass factories, and Portland cement mills, were soon attracted to these towns. A little later gas was being supplied to cities outside of the gas belt. Pipe lines were laid to Wellington, Wichita, Hutchinson, Topeka, Lawrence, Kansas City, Leavenworth, Atchison, and many of the towns between. After ten years of this greatly increased use of gas the supply became less abundant, and now it is feared that the supply from this field may fail at no distant date. [Illustration: OIL WELL, OR “GUSHER.”] In the earlier years the oil was all carried in tank cars, but a system of pipe lines for carrying it was soon laid. Many refineries were soon established. The crude oil is used chiefly for fuel and for machine oil. In the refineries it is made into benzine, gasoline, and kerosene. Vaseline and paraffin are among the by-products. In 1914 oil and gas were discovered in Butler County. Within two years this field was yielding such large quantities of oil that the total production of the State was more than doubled. During the next year, 1917, more than three times as much oil was produced as in 1916, and Kansas had become the greatest oil-producing state in the Union. The output of the Butler County field is still increasing, and its remarkable yield will probably continue for several years. [Illustration: SALT PLANT AT HUTCHINSON.] =Salt.= Salt is found in Kansas as a brine in the salt marshes, and as beds of rock salt lying beneath the surface. The marshes were known to the early hunters and settlers, and through the early years of statehood a little salt was manufactured from this brine. In the late ’80’s the rock salt beds were discovered and the salt-making industry was rapidly developed. The center of the salt industry is now, as it has been from the beginning, at Hutchinson. Salt is found in a large part of Kansas, but the most valuable area extends across the middle of the State from north to south. This great bed of salt is in most places from two hundred and fifty to four hundred feet thick. Some salt is made by crushing the rock salt, but the greater portion is made by the evaporation of brines. The brines are obtained by forcing a stream of water through rock salt.