( oi'resjtondence. 123 
the first place, it should be noted, that the ujjper Ohio and its tribu- 
taries occupy a vast area, and present a very complicated set of phe- 
nomena. Toward the ex])loration of this region and the untangling 
of these phenomena Prof. Chamberlin tells us (p. 22) that he spent 
twenty days. But, secondly, to say nothing of the far longer time 
which I have spent in the study of the |)henomena. Prof. I. C. White, 
a geologist of the highest ability, who has spent his life in that region, 
and surveyed it most carefully, still maintains with great confidence 
that I'rof. Ohamberlin's explanation is utterly inadequate to account 
for all the facts. It should be added, however, that Prof. White's own 
mind has been wavering between the explanation afforded by the 
Cincinnati ice-dam (to whicli he at first gave his unciualified adhesion), 
and that afforded by a siip|)osed extensive subsidence during the 
Champlain epoch (see P)ull. of (tpoI. 8oc. of America, vol. i, pp. 477- 
479). 
In view of these facts, and with additional evidence which I liave 
recently collected, the Oincirmati ice-dam is an hypothesis which still 
gives fair promise of solving many of the geological anomalies in the 
(Quaternary de])()sits of the upper Ohio valley. 
6th. I am sorry to have misrepresented Prof. C-iiamberlin's posi- 
tion with reference to the wanderings of the north pole ; but in this I 
must in part lay the blame upon the Americ.vx Geologist, of which 
Prof. Salisbury was at the time editor, which thus reported I'rof. 
( 'hamberlin's paper: ''Prof. T. ('. (Uiamberlin, in the afternoon, sum- 
marized the standing of several of the theories which have been sug- 
gested to explain the occurrence of the Ice age. After stating that 
the hypothesis of Oroll now fails to account for the plienomeiia, at 
least on tiiis continent, he hastily sketched the theory of elevation as 
the cause of the cold, and offered as in his view most ])robable a 
change of the axis of the earth's rotation" (see A.^rElU('.\x (tEolocust, 
Sept., lS9i, p. 195). This was repeated in a fuller report in the Octo- 
ber number, p. 237. 
7tli. I'inally. in rt'sp(^ct to tlie occurrence in America of palnolitliic 
implements in undisturbed gravel strata of glacial age, 
it is i)ro|ier that 1 should here give a mon^ detailed statement 
than [ have elsewhere done. At the outset I may premise that the 
apparent monopoly of this evidence by Prof. Putnam and his associates 
in the I'eabody Museum at C!ambridge, ^lass., has come about by a 
legitinuite and natural process, which at the same time has probably 
interfered, to a cnnsiderable extent, with the general si)read of the 
spt^cilic inforniiition in hand. iOarly in the investigations of Dr. Ab- 
bott, at Trenton. N. .1.. professor Putnam, who had lately become 
curator of the niiiseum, with its large fund for i>rosecuting investiga- 
tions, satislicd hiinseir of the genuineness of Dr. .\bbott's discoveries, 
and at once retained him as an assistant in the work of the museum ; 
thus diverting to (Cambridge all his discoveries at Trenton. i>iving 
on tiie gronnd during long-continued andextensive excavations made 
l)y the railroad. Dr. .Abbott's opportimities were exceptionally favor- 
