Hopkinsʼ Plate 4. The oriented grain of the crystalline rocks seems to show that they have been modified by the polar magnetic attraction. From Hopkins (1844).

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... forming the most western part of the great northern transverse land mass that extended unbroken far into Asia. Therefore, at the very beginning of Devonian time there came into existence an almost circumpolar land, whose only submerged portion lay in the North Pacific, and which was formed by the union of Laurentia, Baltica, and Angara (see Fig. 434.) The great Canadian geologist, Sir William Dawson, of McGill University, labored long to make known the plant life of the Devonian, and since he termed it the Erian flora after the Erian rocks in which it is entombed, taking the name from lake Erie and the Erie division of the New York state geologists, Suess in 1909 gave the ...

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... the plant life of the Devonian, and since he termed it the Erian flora after the Erian rocks in which it is entombed, taking the name from lake Erie and the Erie division of the New York state geologists, Suess in 1909 gave the continent the name of Eria. It is the old ancestral continent of the modern Holarctic region of the zoölogists (see Fig. ...

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... Their footprints are known in eastern North America in great variety (Figs. 460, 461), but good skeletons are exceedingly rare. In Europe, on the other hand, their skeletons are more common, and, so far as known, the animals were of the same kinds as those of America. From this and other evidence it appears that the great northern continent Eria (Fig. 434) was still intact and was the land across which the plants and animals of Triassic time readily migrated to and fro. Crocodile-like reptiles of the sprawling type (Mystriosuchus, Fig. 458) and other active forms (Aëtosaurus, Pl. 31, Fig. 9) were common. Genuine turtles occur in the Triassic rocks, showing the group originated in the ...

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... glacial deposits (Talchir) preceded the Permian submergence. In North America, tillites seemingly of Permian age are known about Boston, Massachusetts, and striated stones have been reported on Prince Edward Island; in England and Germany also they occur at the base of the Permian. For the complete distribution of these glacial deposits, see Fig. ...

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... must be given. Such evidence relates mainly to the wide-spread deposits of Permian age which have a flora in their lower beds that has been called the Glossopteris flora (Fig. 432). This flora occurs throughout the southern hemisphere, and paleobotanists hold that it could only have been so widely distributed across a continuous land (see Fig. 434). Belief in the existence of Gondwana is widespread among European geologists, but many American workers do not yet believe in it, mainly because they hold strongly to the theory of the permanence of the oceanic basins and continents. Without this continent, on the other hand, paleontologists cannot explain the known distribution of ...

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... the Greater Mediterranean. -To the north of Gondwana lay the great medial ocean which Suess has named Tethys, after the consort of Oceanus (see Fig. 434). The present Mediterranean is a remnant of this once grand middle ocean which widely extended unbroken from France and Spain into the eastern Indian and Pacific oceans, from time to time connecting with the Arctic Ocean by way of the Ural geosyncline. How often it was in open connection with the Atlantic is not yet clear, but that it ...

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... the 1915 edition, Wegener showed a sketch of continents before the Atlantic Ocean had opened (Fig. 30). Since we have already seen the Snider-fit and the Bullardfit, it is appropriate to now call this one the Wegener-fit. Wegener did not try to plot much geologic evidence on this fit-map. But note two geologic elements that he did try to represent by dashed lines: the continuation of the fold-belt from France, Britain, and Ireland ...

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... his drawings seemed to show that the poles had indeed moved, even though polar wander was not a requirement of his theory. The horizontal lines across his globes encourage this misunderstanding. They seem to show the Equator lying across ancient Africa. These horizontal lines were not needed, and were not shown in a few of his globes (such as Fig. 33). Climate indicators convinced Wegener that the continents had moved with respect to the poles, but the evidence could not rule out the possibility of some polar wandering as well. ...

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... for his second textook, Schuchert redrew his map and removed those arrows (Fig. 36). One might suppose that he removed the arrows because they could still not be explained. But in fact, he knew that they now had been explained, by the theory of continental drift. (Fig. 37). When he plotted the distribution of continental ice sheets on this map, the isolated glacial deposits fit together in a single ice cap of ...

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... for his second textook, Schuchert redrew his map and removed those arrows (Fig. 36). One might suppose that he removed the arrows because they could still not be explained. But in fact, he knew that they now had been explained, by the theory of continental drift. (Fig. 37). When he plotted the distribution of continental ice sheets on this map, the isolated glacial deposits fit together in a single ice cap of reasonable size. The directions of ice movement made a meaningful pattern, with ice flowing more or less away from the center, in India, Australia and also South America. Du Toitʼs discussion of the ...

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... cited Du Toitʼs paper and used parts of it. It seems that he started to put more detail on his world map by drawing Du Toitʼs new arrows in South Africa instead of his previous ones (see Fig. 36). But he did not add the new arrows to South America. And he removed the northward-pointing arrows in India and Australia. He had no reason to doubt those data. He must have removed the arrows so that students using this textbook would not be distracted by those ice-flow directions and the new ideas of continental ...

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... presented a map of Permian or Carboniferous Glaciation (Fig. 38). On this map he plotted the data in such a way that glaciation is mostly limited by the same line of latitude. But his written text explained that the Permo-Carboniferous glacial ice actually extended far beyond that limit, toward the ...

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... showed a map of world glaciation in Pleistocene time, where ice-free Alaska and Siberia are clearly visible (Fig. 39). Canada and Scandinavia had been heavily glaciated in the Pleistocene. If they had been at the same latitude in the PermoCarboniferous, why had they not been glaciated then? And why was southern Africa heavily glaciated in the Permo-Carboniferous but not at all in the Pleistocene? Coleman had no answers to these questions, but did not ...

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... paper had few sketch maps and geologic profiles, but they were intriguing. One map showed the close fit of continents in Gondwana, and the huge area of shallow marine sediments that would be shortened and compressed to form the Himalayas (Fig. 43, area c). And the profiles showed how mountain ranges formed by continental collisions (Fig. 44). But his paper must have been a disappointment. For some reason, his large colored map was not included and was totally unavailable to readers. This publication consisted largely of discussion of the rock patterns and the various folds of an ...

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... works (Fig. 53) were not readily avalable to American readers; only his 1922-book was actually translated in his lifetime. His publications on displacement theory were far too similar. His first two papers, in 1912, had the title Entstehung der Kontinente, and his first book-title was nearly the same: Entstehung der Kontinente und Ozeane. Although he ...

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... in fold mountain ranges? Willis avoided putting any numbers on it. But most geologists, even fixists, were forced to accept that continental material had moved hundreds of miles to form the Alps and the Himalayas. That is why Wegener and Argand showed ancient India as being incredibly long in this maps of Pangaea (see Fig. 32) and Gondwana (see Fig. 43). India was presumably shortened by horizontal compression to form the ...

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... for continental drift was extensive. And he accepted that convection currents in the mantle must be the underlying mechanism. But he did not understand convection processes as well as Holmes had done. In Du Toitʼs version, the oceans were not involved in the convection, and the convection cells were flat, with almost no vertical component (Fig. 63). To function properly, convection must be driven by vertical density differences, and could not be mainly horizontal as his figure shows. The North American scientist who understood convection currents best was David Griggs , a geophysicist at Harvard. He published a paper in the American Journal of Science in 1939 that employed theory ...

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... of the main questions at present discussed by geologists is: Do continents drift? To this no definite answer can be given, but it will be possible in the sequel to indicate the sort of evidence that suggests the possibility that, for instance, South Africa and South America once lay side by side (Fig. 307) [Fig. 64]. Perhaps the matter may be settled by measurement, for a succession of longitude observations taken at a particular site in Greenland makes it appear possible that Greenland is nowadays drifting at an appreciable rate towards America. Bailey 1939, p. 19. We have in these few instances noted that Britain formerly enjoyed much warmer ...

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... the glaciated localities extend somewhat beyond the limits of a single hemisphere, it would appear that the earth's crust has not migrated as a whole, but that in late Carboniferous times Gondwanaland was a fairly compact unit clustered about the South Pole, and that its constituent parts have since drifted asunder into their present positions (Fig. ...

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... explained his paleogeographic interpretations even more fully than Schuchert had done, giving more of the details of fossils and stratigraphy. He expanded the discussion of Cambrian faunal provinces (Fig. 73), which I find quite fascinating. These provinces became key evidence for later recognition of the Iapetus Ocean in plate tectonics. Grabau 1921, p. 227-231. Separate Faunal Provinces -In the study of Cambrian faunas it becomes apparent that there are distinct faunal provinces, and that the organisms of one have little or nothing in ...

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... clouds were finally gone from the Atlantic coast on all three maps of Late Cretaceous time (Fig. 83). By then, Pangaea had broken up and the Atlantic Ocean had opened. For the three maps of Cenozoic time, no clouds were shown anywhere on the maps (Fig. 84). When Dunbar wrote that the clouds were "a device to hide critical areas" we can understand this as meaning a device to hide the ocean, which did not yet exist east of North ...