346 PROCEEDINGS OF THE ACADEMY OF [1880. 



b}' the advance of fitting arboreal vegetation, until a point was 

 reached when the present climatic conditions were such as to 

 limit any higher advance of the trees. 



September 21. 

 The President, Dr. Ruschenberger, in the chair. 

 Twenty-eight persons present. 



Bone Caves of Pennsylvania. — Prof. Leidy remarked that in 

 the early part of August, in company with Dr. T. C. Porter of 

 Easton, he had visited Ilartman's Cave, in the vicinity of Strouds- 

 burg, Pa. They had been invited by Mr, T. Dunkin Paret, of 

 that place, who had recently undertaken the exploration of the 

 cave, and had obtained from it an interesting and important col- 

 lection of animal remains, which had been submitted to Prof. 

 Leidy 's examination. 



The cave is situated about five miles from Delaware Water 

 Gap in a ridge which separates Cherry Valley from the valleys of 

 the Pocono and McMichael's Creeks. The ridge is an anticlinal 

 fold of the Ileiderberg or Upper Silurian limestone, and the cave, 

 occupies the axis of the fold and opens in the face of a clitf formed 

 by a cross section of the ridge. An accumulation of debris forms 

 a slope at the base of the cliflT, and above the deliris and just 

 below the arching roof of the cave, a low passage waj^ has long 

 been known into which adventurous bojs would creep. 



Mr. Paret commenced the exploration by having a passage dug . 

 through the del)ris to the entrance of the cave, and then extended 

 the trench within the latter for upwards of a hundred feet, and to 

 a depth siifficient to walk erect. At one place within the cave the 

 digging was carried to^the rock floor. It would thus appear that 

 the cave is occupied by a bed of clay about 10 feet in depth. On 

 this is a thin layer of stalagmite and on this again about a foot of 

 black frial)le earth mingled with animal and vegetal remains. 



No remains have been found imbedded in the. cla}^ nor on the 

 rocky floor in the pit dug through the latter. * 



Prof. Leidy supposed that during the glacial period, a stream 

 of water, from melting snow and ice at a higher level, had made 

 a passage way through the fissured limestone of the anticlinal axis 

 and had left in it the abundant clay deposit. When the cave 

 ceased to be a water course the layer of stalagmite was formed 

 and subsequently the more frialjle eartli accumulated from mate- 

 rials, such as (lust and leaves, blown in and mingled with the 

 remains of animals, occupants of the cave, and of their food. The 

 recess of the cave above the clay floor api)ears to have been too 

 small to be inhabited by the larger carnivorous animals or mah, 

 and therefore no large entire bones of these have been found in 

 the ossiferous stratum. 



