Pseudo evidences may be classified as natural and artificial, and the latter may be separated into accidental and intentional. Nature uses varied and sundry deceptive coloring and stains (black, brown, purple, and other colors) which simulate oil sands including sandstone "dikes" and "veins," limited lenses, and small inclusions of oil sands in surrounding barren material. In addition there are deposits of chemicals which one may mistake for oil deposits. In some instances, migrated or displaced oil has moved into reservoirs of porous igneous or other rocks which are normally incapable of acting as suitable traps for commercial deposits. Other gases or even air may act like petroleum gas in producing springs, water springs, mud volcanoes, and "blow-outs." Practically all of these types of misleading occurrences are of inorganic origin. However, there are rare cases of pseudo seepages caused by animals, insects, or vegetation. In places, a combination of inorganic and organic phenomena produces deceptive deposits, such as the reducing and precipitating action of decaying organic acids on the soluble Fe in marshes and other quiet waters. Under the heading of accidental pseudo oil seepages and sands are the accidental injection of oil into porous sands or rocks from overturned railroad cars, trucks, or tanks, and a subsequent covering of the sands with mud or sand, which eventually were cut into by streams, erosion, or digging that exposed the sands as part of a series of beds. A leakage of oil down a drainage channel can produce the same results. The "discovery" of oil in water wells can usually be accounted for by oil which has been used in lubricating wind mills or pump machinery and which has trickled into the water. Intentional false evidence of oil may be produced in several ways. Among the commonest is the pouring of oil into water wells or into the ground adjacent to water springs in such a way that the oil will gradually reach the water below the surface and emerge with the spring water. Another way is to saturate outcrops of porous sands or other beds with oil and later dig into the outcrop and expose the "oil sand. " A third, and sometimes hard to detect method, is to pour oil into a drilling well thus saturating penetrated sands, and then recovering cuttings or cores of "oil sand." Lubricating stuck casing or drilling equipment by pouring oil in the well produces the same effect, but without sinister motives. Oil injected into a wildcat well may ruin it for information purposes.