1883.] NATURAL SCIENCES OF PHILADELPHIA. 41 



Professor Lewis was not prepared to express such a positive 

 opinion as to its artificial origin. Tiie straight, parallel sides of 

 the specimen, resemble the form of natural cleavage fragments of 

 some sandstones and flagstones. Such cleavage fragments are 

 frequently harder in the centre than along the edges, this being 

 the result of a concretionary force, and if the specimen has been 

 shaped by subsequent w^ater action, the harder central portion 

 would resist action and form the ridge already described.* The 

 regular bevelling at each extremity would, however, be a very 

 unusual form to be produced hj natural ei-osive forces. 



The implement, if such it be, would be the first that has been 

 discovered in the Philadelphia gravel, and would become of great 

 interest in its bearing upon the antiquity of man on the Delaware. 

 The implements found by Dr. Abbott in the gravel at Trenton are 

 of a much more rude type, being closely allied in shape with the 

 palaeolithic implements of the river drift of several European 

 localities. They are never ground down to an edge like the speci- 

 men now described, but are rudely chi[)ped. The Trenton imple- 

 ments, moreover, are made from Triassic argillite, while this one 

 is made from a compact yellowish-brown sandstone. 



As the speaker had endeavored to show* in a former communi- 

 cation,^ the Trenton gravel is a post-glacial deposit made at the time 

 of the final disapi)earance of glaciers from the headwaters of the 

 Delaware, while the Philadelphia red gravel is somewhat older, 

 having been formed during the glacial epoch at a time wdien this 

 region was depressed 150-180 feet lower than its present level. 

 Both gravels are true river gravels. 



Prom the geographical position of the locality where the imple- 

 ment was found, it is probable that it belongs to the older of the 

 two gravels. As, however. Professor Lewis had not seen the gravel 

 at this place, judgment was reserved upon this point. 



It would, indeed, be a curious fact if it were proved that an 

 implement of neolithic type belonged to a gravel older than that 

 which contained only pahi^olithic implements. 



Sliould the specimen under consideration really belong to the 

 gravel, and be proved to be artificial, it will carry back the antiquity 

 of man to glacial times — an antiquity already assigned by numerous 

 discoveries elsewhere. Unlike as this is to the paheolithic imple- 

 ments of Trenton, it is by no means the first neolithic implement 

 repented from a river gravel. 



Mr. John Ford" has discovered a polished stone axe in the 

 gravel forming the outer bluff" of the Mississippi River, near 

 Alton, 111., which is of great interest. This axe, now in the 

 archaeological collection of the Academy, was taken b}^ Mr. Ford 

 from a per()endicular face of gravel freshly cut and exposed by a 

 road cutting ; and, accompanied by a number of fossil land and 



» Proc. Acad. Nat. Sc. (Min. and Geol. Section), Nov. 24, 1879. 

 ^ Proc. Acad. Nat. Sc. Phila., 1877, p. 305. 

 4 



