The Second Lake Alf/onqiiiii. — T<ii//ur. 171 
the eastward uplift, and that until after its independence lake 
Superior was atfected onl}^ by a northward element of defor- 
mation. The eastward uplift oecurred, therefore, at a con- 
siderable time after the aband')nment of the North Bay out- 
let. 
By these facts relating to lake Superior and the Niagara 
gorge we are enabled to put the date of the eastward uplift, 
or rather of its beginning, at a considerable period of time 
after the extinction of lake Algonquin. The water must have 
fallen away from the Nipissing beach at Sault Ste. Marie 
more than 50 feet before lake Superior became independent. 
But a fall of 35 feet at North Bay closed the outlet, and it 
follows, therefore, that the closure took place before the 
Sault began its career. It is probable that the water at the 
Sault fell away even farther — more than 50 feet — before the 
beginning of the eastward uplift, because the submerged Sault 
beach necessarily required a considerable time to attain the 
pronounced development which the Pictured rocks and other 
products of its action show. In a word, the eastward uplift 
began only at a considerable tinie after the independence of 
lake Superior had been com[)leted by the simple northward 
uplift. This is as far, however, as the order of changes can 
be made out at present on evidence which traces forward from 
the time of lake Algonquin. But over against this there are 
facts of another kind which enable us to put the beginning of 
the eastward uplift well back from the present time. 
2"he St. Clair Flats. Not the least im[)ortant of the nuiU}^ 
tilings that find an explanation in this study of lake Algon- 
quin is that curious formation called the St. Clair Hats. It is 
in realit}^ a great modern delta of pure sand. But the waters 
of the St. Clair river, coming directly from lake Huron, are 
almost as clear as crystal. No other stream in that region, 
not even the muddy streams that empty into lake Erie, have 
any deltas, but all have open estuaries instead. Dr. Spencer, 
as quoted above, describes tlie lieavy cutting of the waves 
aU)iig the present sandy shore of tiie east side of lake Huron. 
By their predominant run toward the south the waves are 
constantly carrying the sand in tliat direction, and the same 
is the case in a less degree on the west side. There is on this 
account a c<tustant teiuleiu-v for sand to collect at the south 
