152 



SCIENCE. 



[N. S. Vol. XVIII. No. 448. 



layers. To this part of the formation the 

 name St. Joe limestone has been applied. The 

 St. Joe is sometimes sixty feet or more thick, 

 and often weathers into characteristic pre- 

 cipitous or overhanging bluffs extending for 

 miles along the streams. 



Immediately beneath the St. Joe limestone 

 is a mass of shales sometimes attaining a 

 thickness of fifty feet, known as the Eureka 

 shales. These shales are usually black and 

 papyraceous, weathering into thin flakes or 

 tablets. Throughout the region thousands of 

 springs issue from between the Eureka and 

 the St. Joe. 



Jacobs' cavern is located in the St. Joe 

 limestone some forty feet above the level of 

 Little Sugar Creek. The cave faces south- 

 west, overlooking the narrow valley. The bluff 

 above the cave continues to the height of one 

 hundred and fifty feet or more, the upper part 

 being composed of Boone chert. 



The cave is in fact but a rock shelter, 

 irregularly V-shaped in outline, with floor, 

 walls and roof of limestone. The flat top is 

 composed of a single stratum of limestone, and 

 stratification lines are well exhibited on the 

 sides of the cave. Along the front the entire 

 length of the rock shelter is approximately 

 seventy feet; the extreme depth is fifty feet. 

 Before removing any of the contents the 

 height was from four to seven feet. The 

 floor was covered, however, by two deposits, 

 one of clay and one of ashes, aggregating six 

 feet thick, so that the distance from the lime- 

 stone floor to the limestone roof is approx- 

 imately twelve feet. 



The rock floor was covered to the depth of 

 three feet with clay, usually yellowish-brown 

 in color, containing numerous fragments of 

 limestone. This clay was probably formed by 

 the disintegration of the limestone and so 

 far as noticed has never been disturbed. On 

 the clay was a layer of wood ashes averag- 

 ing three feet in thickness. Throughout the 

 greater part of the cave these ashes were so 

 loose and dry that the men engaged in re- 

 moving them were obliged to use sponges in 

 order to avoid breathing the ashes. In fact 

 several of the men were unable to continue 



the work on this account. Mingled with the 

 ashes and sometimes extending into the sub- 

 jacent clay were slabs and blocks of limestone 

 fallen from the roof. 



At the back of the cave there is a fissure 

 extending upward to the height of ten feet or 

 more, separating the roof of the cave from the 

 rear wall. This fissure, which is probably a 

 master joint in the limestone, is from eighteen 

 inches to three feet wide and continues for 

 some distance beyond the main part of the 

 cave, where it divides into a lower and an 

 upper part separated by a block of limestone. 



All along this fissure and also along part of 

 the back of the cave beyond the point where the 

 fissure extends, there are numerous stalactites, 

 stalagmites and pilasters formed by water 

 dripping from the roof. In places the entire 

 fissure above the level of the roof is filled with 

 this material. The continued dripping of 

 water carrying CaCOj on the ashes covering 

 the floor of the cave has formed a sort of 

 stalagmitic ash breccia often enclosing flint 

 flakes, implements . and bones. In these sta- 

 lagmites charcoal is often present. That this 

 ash breccia was formed gradually and after 

 the deposition of the ashes is proved by the 

 peculiar toadstool-like shape of some of the 

 pillars. It seems from the shape that ashes 

 were first laid down, then the dripping of the 

 water formed the brecciated mass, then other 

 ashes were deposited, other breccia formed, 

 then further deposits of ashes, and so on till 

 the entire pillar was formed. The clay be- 

 neath the ashes near the back part of the 

 cave is in many places cemented by the action 

 of lime forming a clay and limestone breccia. 



Scattered about in the ashes and enclosed 

 in the stalagmitic breccia at the back of the 

 cave were found a number of objects which 

 point to the fact that the cave has been oc- 

 cupied by man. These objects may be divided 

 into eleven groups, of which seven may be 

 considered as witnessing to human occupancy, 

 and four may or may not bear such testimony. 

 The objects are as follows : 



A. Objects witnessing to the human oc- 

 cupancy of Jacobs' cavern: (1) Human bones, 

 (2) pottery, (3) flint implements, (4) stone 



