The Second Luke AI;/ontjin')i. — TaijJt>)\ 101 
basins were lately occupied by an extensive lake, which had 
its outlet eastward across the Nipissing pass at North Bay, 
Ontario. This extinct lake comprised all three of the present 
upper lakes, hut its area was not much greater than their 
present combined areas. Its Avaves made a heavy and unmis- 
takable mark along its shores, and this abandoned beach may 
be easily distinguished from all others and traced continu- 
ously. No other beach of that region has such a clear and 
strong character anil none is so easy of access and identifica- 
tion. Its place shows that tiie water stood about 45 feet 
higher than lake Huron stands now in the straits of Mackinac 
and 50 feet above tiie level of lake Superior at Sault Ste. 
Marie. The connection of that time between lakes Superior 
and Huron was a narrow strait, probably with a sluggish cur- 
rent, but certainly with no "sault" or rapids like those of the 
present river. Since the time of this lake the lands which 
formed its shores have been slightlj^ tilted upward toward the 
north-northeast, and its southwestern shores are submerged 
beneath the present waters of the lakes. As we shall see 
presently, this extinct lake is destined to hold an important 
place in recent geological histor3^ For it marks a transition 
stage between the present order of things and a time when the 
salt water of the ocean came into the great lakes through a 
strait over lake Nipissing, 25 miles wide and 500 feet deep. 
Dr. J. W. Spencer has already tlescribed a postglacial lake 
which occupied the same basins, but his conception of its age, 
epochs and stages is not the same as is here set forth. He called 
it lake Algonquin. Following his usages as closeU^ as possi- 
ble, 1 adopt this name for the lake described below. \>'hi)e 
it differs in some important respects from Dr. Spencer's lake 
Algonquin, the abandoned beaches of the two being entirely 
independent throughout, its outlets were the same and it will 
probably be found in the end that this lake was only a sec()iul or 
later epoch of the same lake which he described.* Lake Algon- 
*"Nc)tes on th(! Ori<iin and History of tlio Girat TiaUcsof Xortli Anifi- 
ica," by .1. W. SixMiccr, Proc. A. A. .\. S., vol. xxxvh, ISSS. In ihf iioic 
at the bottom of [jaji;i; l!)i* dctinilions ari' ^ivcn lor tlic aiiciciil ■'Laiircii- 
tiau" and "Pii-iii'an" rivers, and also for lakes ■■,Vl^-on(|uin"" and ""Iro- 
([uois." Lake Ai;;on(inin is defined as liie anrienl •'Hnron-Micliii;an- 
Snperior lake." Tiie name "Alj^-'oniinin"' is applied also lo ••|lie beach 
which marked its [lake Al^-on(|nin"s| shores, and llii' ri\er wliicli dis- 
cliar^-ed ils waters b\- the Trent valle\-."" lieiiinninii' on i lie precedi iii,'- 
