Septembee 27, 1907] 



SCIENCE 



399 



held in the Ontario basin while the Lauren- 

 tian ice-mass occupied the St. Lawrence 

 valley and forced the overflow by the Rome 

 outlet to the Mohawk and Hudson valleys. 

 This original Iroquois outlet was efi'ective 

 for several thousand years, and determined 

 the water-level for nearly the whole exist- 

 ence of the glacial waters. 



When the ice-body weakened, and the 

 front receded on the salient which projects 

 northeastward from the Adirondacks into 

 Canada, a lower escape for the ice-dammed 

 waters was opened across the Covey hill 

 ridge, precisely at the international boun- 

 dary. 



"The Gulf," as it is locally known, is a 

 great cut in Potsdam sandstone, long since 

 noted by Emmons and Gilbert, and re- 

 cently described by Woodworth. The 

 present altitude of the head of the Covey 

 outlet is over 900 feet, but at the time it 

 was opened the locality was about 460 feet 

 lower than to-day, and the initiation of the 

 river flow must have been inferior to the 

 Rome level, which is now 440 feet. 



After at least many centuries of flow this 

 predecessor of the St. Lawrence river, 

 carrying the overflow of the second stage 

 of Iroquois waters (or Hypo-Iroquois), was 

 extinguished by the ice recession opening a 

 yet lower pass, on the north slope of Covey 

 hill. This third phase of the Iroquois 

 waters was short lived and of rapidly fall- 

 ing levels, the river-flow past the ice-front 

 only terracing the sandstone slope. 



When the waters were lowered about 450 

 feet below the Gulf channel, they became 

 confluent with the oceanic waters, and the 

 Ontario basin was occupied by the Gilbert 

 gulf, a branch of the Champlain or 

 Hochelogan sea. 



On Friday the parties from Mooers and 

 Plattsburg met at Chazy where Professor 

 Gushing and Dr. Ruedemann showed the 

 visiting geologists many interesting fea- 



tures of the Chazy limestone, the local suc- 

 cession of beds, the characteristic fossils, 

 the faults, and the dissection which have 

 produced the present topography. After 

 supper, while waiting for the train to 

 Plattsburg, the party sat on the hotel porch 

 and listened to a talk by R. Rued,emann on 



THE LOWER SILURIC PALEOGEOGRAPHT OF 

 THE CHAMPLAIN BASIN 



The relations of the faunas of the Beek- 

 mantown, Fort Cassin, Chazy, Black River, 

 Trenton, and Utica beds to those of the At- 

 lantic and Pacific basins and the Missis- 

 sippian sea were discussed, and by means 

 of these relations the probable marine con- 

 nections of the Chazy basin and the Levis 

 channel with the oceanic basins traced. It 

 was suggested that the Beekmantown sea, 

 while extending as far as the Newfound- 

 land emba3rment, held an American epi- 

 continental fauna; that the Fort Cassin 

 fauna did not reach Canada, but flourished 

 in the Appalachian trough to the south of 

 the Chazy basin, and also spread westward 

 into the epicontinental sea. The typical 

 Chazy fauna is thus far recorded only for 

 the Chazy basin and the southern Ap- 

 palachian trough. It extended as far as 

 the Mingan islands, and came probably 

 from the Atlantic basin. There is also evi- 

 dence that it had some connection with the 

 American epicontinental sea. 



The Black River and Trenton faunas, 

 while largely American in their aspects, 

 contain European species as the first of the 

 Lower Siluric; and the connection of the 

 Trenton sea with the Atlantic ocean can 

 not be doubted. In Utica time the channel 

 became so wide that an oceanic current 

 could enter the epicontinental sea from the 

 northwest, bringing with it new faunal ele- 

 ments, and spreading mud shales over a 

 large area of eastern North America. 



The evidence of a deeper sea in the 



