340 



PAST CLIMATES AND CLIMAXES. 



spot cycles at this time must rest upon a study of the rings of growth of the 

 buried trunks of the different peat horizons. Huntington's studies of the 

 cycles of historic times make it probable that all grand sun-spot cycles consist 

 of major cycles of 1000 ± years, and of 300 to 400 years, and these of cycles of 

 100 to 150, 72, 35, 21, 11, and 2.5 years. While all of these sun-spot cycles 

 telescope into each other, so to speak, the volcanic episodes and cycles fall in 

 independently and irregularly to modify them. Thus, while it is manifestly 

 impossible to construct a complete series of climatic cycles, it is possible to 

 indicate their essential correlations in a fairly plausible manner. If the cycles 

 of the Permian and Pleistocene glacial times are assumed for all cooled or 

 cold periods, and the sun-spot cycles and volcanic episodes of historic times 

 for all periods, we obtain a complete though necessarily hypothetical picture 

 of the march of cycles throughout geological times. 



The sequence of grand and major deformational cycles is best shown in 

 Schuchert's chart of geological climates, which is shown in figiu-e 26, with the 

 addition of major volcanic periods. The striking correspondence of the curves 

 of climatic factors and of biotic sequences is the convincing feature of his 

 interpretation. The table below is an endeavor to show the correlations of 

 the various kinds of climatic cycles from the grand deformational cycle to the 

 normal sun-spot cycle of 11 years. 



Table oj climatic cycles. 



Grand defonnation 

 cycles. 



Major deformation cycles. 



Grand sun-spot cycles. 



1. Eophytic. 



2. Paleophytic. 



{■• 



3. 



3. Mesophytic. 



4. Cenophytic. 



Proterozoic. 



Proterozoic. 



Cambrian. 



Ordovician. 



{Silurian. 

 Devonian. 

 Misaissippian. 



/Mississippian. 

 \Pennsylvanian. 



I Permian. 

 Glaciation. 

 Triassic. 

 Jurassic. 



/Comanchean. 

 \Cretaceous. 



fCretaceous. 

 \Eocene. 



roiigocene. 

 \Miocene. 



Pliocene. 



Pleistocene. 

 Glaciation. 



Human or Recent. 



Glaciation. 

 Glaciation. 



Glaciation. 



Glaciation. 



f9 or 10 glacial-interglacial cy- 

 1 cles in Australia. 



Cooling. 



Cooling. 



1. Jerseyan-Aftonian Cycle. 



2. Kansan- Yarmouth Cycle. 



3. lUinoian-Sangamon Cycle. 



4. lowan-Peorian Cycle. 



5. Earlier Wisconsin Cycle. 



6. Later Wisconsin Cycle. 



