in Eastern North America. 409 



western European Caledonian deformation, when grand 

 mountains were made all the way from Britain across 

 Norway far into arctic Spitzbergen. This movement de- 

 veloped the very thick Old Eed sandstone, through whose 

 fossils we get the first good vista of the animals of the 

 fresh waters and of the first known land floras. But 

 where is the student of Historical Geology who would 

 divide the Paleozoic into twT> eras, one to embrace the pre- 

 Devonian periods, and another the post-Silurian ones? 

 If the Europeans did this, would we Americans follow 

 their example, since we have no Caledonides and have 

 great difficulty in deciding where the line should be drawn 

 between the undeformed Silurian and Devonian forma- 

 tions f We would be more in favor of dividing the Pale- 

 ozoic into two sub-eras at the close of the Devonian, for 

 at this time we have decided mountain-making and of a 

 strength not far from that of the Caledonides. And in 

 this the Europeans might agree. 



In regard to the minor orogenies, the disturbances, 

 the writer's views have changed somewhat with wider 

 knowledge. We now know that the deformations do not 

 all fall at or near the close of the accepted periods, as was 

 formerly stated. It is still true, however, that most of 

 them do occur in the last third or fourth of the periods as 

 they are now defined. The exceptions to the rule are that 

 mountains were made in Europe between the Lower and 

 Middle Cambrian, the Upper Cambrian and Ozarkian, the 

 Middle and Upper Ordovician, and the Tournacian and 

 Visean or the Waverlian and Tennessean (see Figs. 4' 

 and 5). These are facts, however, that appear only to 

 make for a dismembering of the old and accepted periods. 

 A revision of the periods, on the basis of diastrophism, 

 would then place all of these orogenies in the latter part of 

 the redefined periods. On the other hand, there are yet 

 other orogenies that do not point this way. In New- 

 foundland, block-faulting and apparently folding as well 

 occurred after Normanskill time of the Middle Ordovician 

 (see Fig. 2). The most striking exception to the rule, 

 however, fa the Pennsylvanian, with its various crustal 

 pulsations ; according to the regions studied there are 

 either one or two that fall near the middle of this period. 

 If in addition we take cognizance of the thick sedimentary 

 deposits, then orogeny also took place in earliest Cham- 



