Davis.] 
334 
[Nov. ig, 
terraced the clays of the Marcellus valley ranch deeper than 
they are terraced by the Catskill. The cross valley of the 
Kaaterskill is evidently not post-glacial ; it is too wide for a 
valley of so young a date ; and it can hardly be regarded as of 
glacial excavation, as it extends across both the local rock struc- 
ture and the trend of glacial motion. It must therefore be 
chiefly of preglacial origin. As such, it offers a much more 
likely course for the preglacial cross valley of the Catskill than 
the present shallow notch at Leeds. But even the Kaaterskill 
cross valley is not so deep as the rock bottom of the Marcellus 
valley ; and hence it is highly probable that both of these trans- 
verse stream courses are of post-glacial, superimposed origin. 
The preglacial course of these streams east of the Marcellus valley 
cannot now be certainly defined. 
The course of the Catskill southeast from Leeds is chiefly 
upon the rocks for two miles ; but the walls of the valley are not 
often so nearly vertical as in most post-glacial gorges or chasms ; 
it is therefore probable that the Catskill here flows along the 
course of some small preglacial stream, whose head may have 
been near Leeds ; its divide from the Marcellus valley being 
naturally placed on the hard rim of Corniferous limestone, over 
which the Catskill now falls. Had it not been for the compara- 
tively high level and considerable strength of this rim, the valley 
filling above Leeds would be much more deeply terraced than it 
is. 
5. Briefly then, the Champlain submergence of the Hudson 
valley allowed the formation of the cobbly delta near Cairo in 
the fiorded valley of the Catskill, and the deposition of the 
Hudson clays in the deeper waters of the main valley. Since 
emergence from the Champlain depression, the Catskill above 
Leeds has excavated a flood-plain meadow in its valley-filling; 
but below Leeds it has been turned from its former course and 
superimposed on the Corniferous ridge. The height of the old 
delta of the Catskill is now 280 feet above sea-level ; and the 
flood-plain near Leeds is a hundred feet lower. The latter 
would be lower, still if the notch in the Corniferous ridge at 
Leeds had been deeper. 
Baron Gerard de Geer, of Stockholm, spoke of his exploration 
of the fossiliferous marine beds, belonging to the Champlain 
