ane THE JOURNAL OF GEOLOGY. 
is cut by a narrow gap, whose bottom is 303 A. T. Under cer- 
tain conditions this gap might have served as an outlet for a 
brief period. Examination of the gap failed to reveal data 
which could be regarded as proving either that the lake did or 
did not drain through it at any time. 
The drift-filled gap at Short Ffills—\West of Short Hills the 
crest of Second mountain is broken by a sag whose bottom has 
an elevation of 380 feet, an elevation 170 to 200 feet lower than 
the average height of the trap crest of the mountain. The 
terminal moraine crosses Second mountain through this sag. 
Some years since a deep well was bored just below the summit 
of this sag at an elevation of 370 feet. The well was sunk 200 
feet without reaching the trap rock. Vhe rock bottom of this gap, 
therefore, must be below 170 feet A. T. There is good reason to 
believe that it is much below this figure. A quarter of a mile 
east of the Short Hills depot, at an elevation of 200 feet, there 
is a well 200 feet deep. At this depth, that is at sea level, rock 
was reached. This well is located in the shale valley between 
First and Second mountains, and is in line with the gaps in Sec- 
ond mountain west of Short Hills, and in First mountain at 
Millburn. These facts and relations clearly indicate a deeply 
buried channel across Second mountain at Short Hills, and across 
First mountain at Millburn, the rock bottom of which at one 
point between the two trap ridges, is known to be at sea level. 
If the rock bottom at the gap in Second mountain be no lower 
than 170 feet—the bottom of the boring —the preglacial stream 
must have had a fall of 170 feet on the south face of Second 
mountain. The width of the gap is such as negative this con- 
clusion. It is so great as to indicate that the stream which 
occupied it was of considerable age. It is probable, therefore, 
that the bottom of the rock gap in Second mountain is very 
much lower than 170 feet, the height at which the boring 
ceased. 
It follows, therefore, that the main drainage of the Upper 
Passaic basin in preglacial times was almost certainly through 
the Short Hills and Millburn gaps. Manifestly Lake Passaic 
