102 The Amen'cdu Geologist. February, 1895 
(luiu a;^ (lescriln'cl in this article isdeilnecl as a post^'lacial lake, 
now extinct, but which recently (since the marine invasion) 
had its outlet eastward across the Nipissin^- pass at North Bay, 
in the province o1' Ontario. 
Tlie great al)andoned shore line wiiich marks the highest 
level of lake Algonquin as just defined is known as the Nipis- 
sing beach, and its extension westward from North Bay along 
the north coast of lake Huron and the south coast of lake 
Superior to Dulutli has been described by the writer in other 
articles. It is the object of the present paper, after first trac- 
ing the identity of theNipissing beach to points farther south, 
to sum up our present knowledge of the whole extent of lake 
Algonquin and to tell as much as is now known of the history 
of its subsequent deformation. Most of the facts referred to 
are contained in the following series of descriptive articles, 
which are given below in the order of their publication and 
Avill be referred to hereafter by number. The maps which 
accompany these papers show the details described much bet- 
ter than the one which illustrates this article.* 
p.iije is an account of the dismembermt'nt of "lake Warren" and of the 
formation of lake Algon(iuin with its Trent valley outlet. Evidently 
Dr. Spencer did not know at that time of the abandoned river outlet at 
the Nipissing' pass, northeast of Georiiian l)ay. liut he lias since recog- 
nized this fact. When we come U) discuss in another paper the relations 
of the higher shore lines of the up])er lakes it will be shown that lake 
Algon(iuin has ])robably had two distinct and separate epochs of exi.st- 
ence, both in postglacial time, and the iVlgonquin beach, extending from 
near Port Hm-on to a point north of Kirkfield, Ontario, where Dr. Spen- 
cer's tracing ceased, is probalily mereh' a deformed or elevated shore-Hue 
of the first epoch of the lake's existence. There is considerable evidence 
to siq)i)ort this view. The lake described in thispaper is then in reality 
the .vecowr/ lake AlgoiKiuin. If Ihi' Algonquin beach is not the shore of 
a first lake Algon<iuiii. then it is merely a much deformed extension of 
the Iro(|Uois beach 
In coinersalion, \)v. Spencer inroi'incd llir wi-il<M- lately that the sup- 
posed Trent valley outlet had been found to be obstructed below the 
place of his i)revious observations and had i)robably not been an outlet 
at all. The two epochs of lake Algoiupiin's existence were sep- 
arated by a long jteriod of time during which the sea entered the 
basin of the upper lakes through the ancient Nii)issing strait. During 
this interval great iq)lifls took place and produced large deformations 
of the marine shores and also of the shores of the first lake Algonquin. 
J^ut all this ]>rece(les the tiine of the events discussed in this payier, and 
inasmuch as the first ('jjoch of the lake's existinice has not yet b(>en dis- 
cussed, it is not deemed necessary t<j use the jilirase "second hike .\lgon- 
quin" throughout this article. 
*.\]1 these papers except the first and sixth were ])ublished while I 
was absent in I'^.urope. so thai 1 had no chance to see the j)roofs. Con- 
