426 FRANK BURSLEY TAYLOR 
ing a series of complex loops, that the system appears at pres- 
ent confused and a complete and simple series is not easily 
made out. The moraines of the Saginaw lobe in all probability 
make a simple series of at least eight or ten members, but they 
have not yet been fully explored. The chief element of con- 
fusion in these several areas appears to be due mainly to the 
influence of a relatively complex topography. There may have 
been other causes of complexity, but the land relief is clearly 
the most important. 
The individual moraines of the Cincinnati-Mackinac series 
are also as a rule simpler in their reliefs, in the curves by which 
they cross the valleys, and the intervals between them are wider 
and more regular. .Their relations to each other and to the 
adjacent higher lands are also simpler. 
On account of their completeness and simplicity, therefore, 
the moraines of the Cincinnati-Mackinac series constitute the 
best body of facts now known for the study of the cause of the 
oscillations of the retreating ice-sheet, and there appears to be 
little prospect of ever finding a better one. With few exceptions 
a comparison of other moraine series shows at once that the 
reason the Cincinnati-Mackinac series is so simple is that the 
land relief which the ice encountered along this line was of the 
simplest sort. Such a comparison in nearly every instance 
strengthens the conclusion that if the ice-sheet had moved over 
a perfectly plane surface the moraines would have been laid 
down at regular intervals or else at intervals varying progress- 
ively in a regular way. In short, the departure from perfect 
simplicity and regularity in the moraine series of any ice-lobe 
seems to be ina general way proportional to the magnitude, 
number, and complexity of arrangement of the larger topo- 
graphic features which it encounters. 
KNOWN PERIODIC OSCILLATIONS OF CLIMATE. 
It has been supposed by many, and apparently with good 
reason, that northern lands were elevated to relatively high 
altitudes during the Iceage. This is held by some to have been 
