564 The Theory of a Glacial Dam at Cincinnati, etc. (June, — 
ter of boulders was by my barometer 4 50 feet above the river, and 
the water-shed was at least a hundred feet higher. Two of the 
boulders are veritable specimens of the jasper conglomerate, $o 
abundant about the outlet of Lake Superior. Granitic boulders 
and striated pebbles were also found at numerous other points 
over the northern part of Boone county, from Greenwood lake to 
Bellevue. Glacial accumulations also occur upon all points of 
the river north of this down to the river valley. It thus appears 
that from Moscow, in Clermont county, about twenty-five miles 
above Cincinnati, to Petersburg, Ky., about the same distance be 
low Cincinnati, that is, for a distance of about fifty miles, the val- 
ley of the Ohio was for a short time during the glacial period 
filled with ice, forming an obstruction to the water at least 550 
feet high. The water: shed to the west, between the Licking and 
the Ohio, is nowhere less than this height. Walton station, se 
enteen miles south and a little to the west of the water-shed, !$ 
473 feet above the river, 913 feet above the sea. 
-= Throughout nearly its whole extent the Ohio river oe 
narrow valley of erosion less than a mile in width, and from 
hundred to five hundred feet in depth. There are epe 
in this trough wherever tributaries come in, either from the 1 
lleys of erosion 
or from the south, which also uniformly occupy v4 
; i size 
of corresponding depth, the width varying according to the 
of the stream. | 
this supposed 8è 
It is evident that during the continuance of pee" 
‘cial dam at Cincinnati, a narrow lake corresponding p d all it 
the ice-barrier, must have extended far up bedaa Licking in 
tributaries; among which may be specially noted. the a 
Kentucky, the Kanawha in West Virginia, the A le 
Monongahela in Pennsylvania. The difference w . 50 
of Pittsburgh and Cincinnati is about three hundres merge 
a barrier of six hundred feet at Cincinnati would Je 
city of Pittsburgh to a depth of about three hundre a 
It is also evident that if there was, for any — ught t0 
‘such a glacial back-water dam as is supposed, ther en 
arking 
margin. Such evidence was not long in com! 
is all the more significant because furnishe 
ties. In March, 1883, I read a paper before 
Natural History in which I reported the main 
the Boston 5 | 
facts just ree? 
