282 E. H. WILLIAMS, JR. — EXTRAMORAINIC DRIFT. 



have further discussed the subject ; but the comment of the state geolo- 

 gist on page 37 is all that remains. He notes : " Professor Prime suggests 

 in his report a possibility that the remarkable evenness of the limestone 

 plain may be partly due to a drift deposit." This suggestion is qualified 

 by the state geologist on the next page in the statement: '' The drift de- 

 posit which helps to give a plain-like aspect to the limestone belt is not 

 unstratified glacial moraine matter, but is a superficial bed of stratified 

 sand and gravel distributed by and in water." The finding of a few fiat 

 pieces of syenite is proof to him that the deposits are local, and he dis- 

 misses the subject with the statement that the Bethlehem gravels are 

 either a "high-flood river deposit, or else ancient high-level river-channel 

 deposit ; " attributes the latter to an old bed of the Lehigh which has cut 

 anew channel through solid rock for 80 feet, and brushes aside Professor 

 Prime's theory with the remark that the flatness of the limestone is not 

 due to any kind of a supposed covering of local drift. 



In 1882 Professor I. C. White discusses the "moraine " found by 'Mr 

 Chance at Lehigh Gap (G6) as follows: ': The ice undoubtedly passed 

 as far west as the Lehigh river, because there we find the old channel of 

 Aquanchicola creek choked up with drift, and the, stream compelled to 

 cut a new one around it to the south through the solid strata, before 

 entering the Lehigh." 



Of the recent findings in the region note will be made only of the 

 location of a " pebbly terrace " at Lehighton, by Professor G. F. Wright,* 

 75 feet above the river. 



Area Studied. 

 topographic features. 



The accompanying map, plate 9, shows the region examined during 

 the past year of 1893.t Only that part south of the Blue ridge was 

 studied with any attempt at thoroughness, owing to the limited time at 

 my disposal. It is proposed to finish this portion during the coming 

 ,year and to extend the work beyond the Ridge. Elevations are based on 

 mean tide, and the points noted are indicated on the map by minute 

 circles. The terminal moraine of ^Messrs Lewis and Wright is shown by 

 double lines of open circles ; the limits of the furthest ice invasion by 

 the larger black dots, and the southern limit of the larger bowlders by 

 the smaller ones. Interrogation points are placed where doubt exists 

 as to the position of the two latter lines. The dotted line from Naza- 



* Proc. Acad. Nat. Scil, Philadelphia, 1892, p. 476. 



t My assistant was Mr Joseph Barrell, and I desire to make suitable acknowledgment of the valu- 

 able work done by him. 



