188 The American Geologist. March i89o. 
ten feet between the south and north parts of the same building enclos- 
ure. No doubt this preglacial channel was uniform in depth to the old 
bed of the Ohio — about one hundred and fifty feet deeper than at 
present. Both on the Kentucky and Indiana sides of the river there 
are several depressions and raised beaches, and after the parting 
above the falls it would be difllcult to determine which was the main 
channel of the preglacial Ohio. Probably the largest branch was on 
the Kentucky side, although the Indiana valley is the most extensive. 
This much is certain, however, that the site of the falls in preglacial 
times was an island, and must have stood up more than a hundred 
feet above the level of the surrounding waters, for as we have seen, 
the old channels are filled in at least one hundred and fifty feet. This 
island, covered doubtless with a luxuriant vegetation, the wide, pre- 
glacial valleys and countless streams, must have formed a picture 
beautiful to behold. On the Indiana side of the falls the old and new 
channels come very close together, so close in places that only a bank 
of clay or a thin edge of rock separates them. In fact, there are places 
over the falls where the present current of the river runs in an old pre- 
glacial channel, making the bed of the present stream much deeper in 
some places than others, but for the most part the falls of the Ohio at 
Louisville consist merely of a shallow channel worn in the surface of 
the preglacial island already referred to. 
The old channels being filled in with glacial debris the river was 
forced into its present course. The amount of post-glacial erosion has 
been very slight as the present channel does not admit of the passage 
of vessels of the lightest draft except at very high water ; therefore a 
canal had to be constructed to avoid the falls and permit navigation. 
From personal observation the writer, as already intimated, is con- 
vinced that most of the rock erosion took place, not during nor since 
the ice age, but in preglacial times. 
Louisville, Ky., Feb. S, 1S90. John Bryson. 
Mr. H. T. Cresson and the Delaware river dwellings. A gener- 
al impression has been held for the last two years that there were 
river dwellings on the Atlantic coast. This impression was gained 
from a letter which was published in the American Antiquarian for 
November, 1887, entitled "Eiver dwellings on the mud flats of the 
Delaware river." This letter was written by Mr. H. T. Cresson, and 
was published exactly as it was written, title and all. The letter was 
quoted by Mr. H. AV. Haynes in the "Narrative and Critical History," 
with the addition of a sentence stating that he, (Mr. Cresson) has 
also kindly sent to the writer (Prof. Haynes) a small illustrative col- 
lection from each site for his study." Mr. Cresson, after two years 
time, seeks to withdraw from his position about "river dwellings," 
but in order to do so furnishes to Science a letter which he pretends is 
a copy of the one sent November, 1887. There are several discrepan- 
cies between the two letters, which, if you will allow me, I would be 
glad to set before your readers. They are as follows : 
