JACOBS CAVERN, a cavern in latitude 36° 35´ N., 2 m. E. of Pineville, McDonald county, Missouri, named after its discoverer, E. H. Jacobs, of Bentonville, Arkansas. It was scientifically explored by him, in company with Professors Charles Peabody and Warren K. Moorehead, in 1903. The results were published in that year by Jacobs in the _Benton County Sun_; by C. N. Gould in _Science_, July 31, 1903; by Peabody in the _Am. Anthropologist_, Sept. 1903; and in the _Am. Journ. Archaeology_, 1904; and by Peabody and Moorehead, 1904, as _Bulletin I._ of the Dept. of Archaeology in Phillips Academy, Andover, Mass., in the museum of which are exhibits, maps and photographs. Jacobs Cavern is one of the smaller caves, hardly more than a rock-shelter, and is entirely in the "St Joe Limestone" of the sub-carboniferous age. Its roof is a single flat stratum of limestone; its walls are well marked by lines of stratification; dripstone also partly covers the walls, fills a deep fissure at the end of the cave, and spreads over the floor, where it mingles with an ancient bed of ashes, forming an ash-breccia (mostly firm and solid) that encloses fragments of sandstone, flint spalls, flint implements, charcoal and bones. Underneath is the true floor of the cave, a mass of homogeneous yellow clay, one metre in thickness. It holds scattered fragments of limestone, and is itself the result of limestone degeneration. The length of the opening is over 21 metres; its depth 14 metres, and the height of roof above the undisturbed ash deposit varied from 1 m. 20 cm. to 2 m. 60 cm. The bone recess at the end was from 50 cm. to 80 cm. in height. The stratum of ashes was from 50 cm. to 1 m. 50 cm. thick. The ash surface was staked off into square metres, and the substance carefully removed in order. Each stalactite, stalagmite and pilaster was measured, numbered, and removed in sections. Six human skeletons were found buried in the ashes. Seven-tenths of a cubic metre of animal bones were found: deer, bear, wolf, raccoon, opossum, beaver, buffalo, elk, turkey, woodchuck, tortoise and hog; all contemporary with man's occupancy. Three stone metates, one stone axe, one celt and fifteen hammer-stones were found. Jacobs Cavern was peculiarly rich in flint knives and projectile points. The sum total amounts to 419 objects, besides hundreds of fragments, cores, spalls and rejects, retained for study and comparison. Considerable numbers of bone or horn awls were found in the ashes, as well as fragments of pottery, but no "ceremonial" objects.