1895.] NATURAL SCIENCES OF PHILADELPHIA. 199 



our Delaware. Near the northern entrance to the Water Gap are 

 low rapids, over the Clinton rocks; just after the river accomplishes 

 its passage through the mountain it falls in a succession of low 

 rapids over the Hudson River slates. 



For many miles both above and below these two sets of rapids the 

 average depth of the water is only six feet, according to the Geolog- 

 ical Survey, but between them, about a mile and three-quarters be- 

 low the upper, and a quarter of a mile above the lower rapids, is a 

 spot where the river has a surprising depth; no two authorities agree 

 concerning the number of feet. In 1892 the engineer of the little 

 launch which plies to and fro in the Gap, said: "It is 35 feet 

 deep." L. W. Brodhead writes me: "We took soundings about 

 forty years ago and made it 45 feet;" and he adds, "a sounding 

 some years previous reached 60 feet, while a century earlier it was 

 thought to be unfathomable." In Penna. Geol. Sur. Rept's. , 

 Vol. G6, the depth is given as 51 feet, while a local Guide Book 

 gives 70 feet. 



Two agencies" are, no doubt, slowly lessening this remarkable 

 depth. The gradual cutting down of the whole river bed from this 

 point to sea level and the slow filling of the pool, by the debris 

 dropped into its quiet waters in times of freshet. 



At the north entrance of the Water Gap the bed of the river is 

 nearly 1,500 feet wide; in half a mile it has contracted to 400 feet 

 and in the next mile reaches its narrowest, 350 feet. This portion 

 ;s nearly a quarter of a mile in length, its walls, 1,000 feet high, 

 rise at an average angle of 45°. From 350 feet the channel 

 suddenly widens to an oblong pool 500 feet wide and about 900 feet 

 long. This pool is bounded by nearly 900 feet of Pennsylvania 

 shore which rises, steeply, to a height of 1,100 feet. The New 

 Jersey side stretches in a beautiful curve, 2,100 feet long, and rises 

 in part a sheer precipice of 1,000 feet, with 200 feet of steep rock 

 still above that. This great curve rounds to the south and ends 

 suddenly at the Point of Rocks. It is just opposite this point and 

 not far from the New Jersey shore, the extraordinary, deep water 

 before described is found. Here, I believe, is the centre of the 

 amphitheatre of the gorge of the north-flowing Delaware and this 

 deep pool marks the spot where the waters of the great river plunged 

 into the chasm. But the solid rock wall over which they fell has 

 been breached by a channel 400 feet wide. Through this opening 



