In his expectation that he would rebuild German meteorology and train a new generation of meteorologists, Alfred pressed forward with his plan to habilitate at the University of Hamburg, an institution that had reopened its doors in March 1918 and would offer its first full semester of courses in the fall of 1919. Writing from Großborstel in early July 1919, he requested permission from the dean of the mathematical-scientific faculty at the University of Hamburg to be allowed to transfer his habilitation from Marburg to Hamburg. He asked to be named an instructor in meteorology and geophysics and noted that he had been told that, in association with his appointment as the meteorologist of the German Marine Observatory, “there would be no obstacle to a possible instructorship at the University of Hamburg in consequence of his appointment.” He also noted that, in expectation of this appointment, he had “recently refused a call to be director of the Baden Central Bureau of Meteorology and Hydrography, which came with the promise of a teaching appointment in Meteorology at the Technical Institute in Karlsruhe.”40 It had been no great loss for Alfred to turn down the call to Baden and Karlsruhe; this state was the new southwestern borderland of postwar Germany now that Alsace had been returned to France, and it was at a disadvantage from the standpoint of observation—shielded from a full range of weather by the Jura Mountains to the southwest.
He sent this letter off at the end of almost three months of intense work, and he was anxious for a vacation. Ordinarily, in July, they would all have gone to die Hütte, but rail travel through Berlin was still a problem, and they had other resources nearby. Alfred, Kurt, and Else decided on a hiking tour in Schleswig-Holstein to the north, in an area known as the Holsteinische Schweiz, a forest and lake district very like the Ruppiner Schweiz in the Brandenburg of Alfred’s youth. Alfred and Else took their first hike together since the fall of 1918, when she had come to Sofia. Hiking along the shores of the beautiful lake known as the Plöner See, they could see the sailboats in the fresh summer breeze, and this, like the rest of the landscape, reminded them of the pleasures of their youth.41
On the trip, enjoying a freedom they had not known for the many years of war and separation, they could actually plan something besides a brief rendezvous, or a way to get more food and fuel. Over the course of several evenings, they (and Kurt) decided that they would buy a sailboat—not a small open boat like the one that Alfred and Kurt had sailed in their childhood, but a 9-meter (30-foot) boat with a full cabin and galley. There were many such boats for sale currently in Hamburg, and they could obtain one at a price they could afford to share; they would be able to sail every weekend if they wished. Hamburg, 100 kilometers (62 miles) inland from the sea, was at the narrow end of the great estuary of the Elbe River which opens to the North Sea at Cuxhaven. When the tides were right, they would be able to ride the flow all the way to the ocean and back again, catching the outgoing tide on a Saturday morning and the incoming tide the following Monday.
Returning to Hamburg from their trip, they immediately set about finding a boat, and by early August they had found a Kajütkreutzer (cabin cruiser), a 9-meter gaff-rigged ketch, in wonderful condition. It was in many respects a greatly enlarged version of the 3-meter (10-foot) boat of Alfred’s childhood, and thus familiar, but with the wonderful addition of the cabin with berths, a head, a larder, and a galley.
The purchase of the sailboat led to another idea. They had planned to go and see Alfred’s mother, Anna, at the end of August, in the break between the summer and fall semesters, and immediately prior to Alfred taking up his position as successor to Wladimir Köppen at the observatory. They decided that it would be fun to take Anna sailing. She had been largely housebound for years and was increasingly lonely and isolated after Richard’s death. Still partially paralyzed from the stroke she had suffered in the summer of 1913, she was nevertheless alert. Between 27 August and 6 September they sailed with her through the chain of lakes in Brandenburg which Alfred and Kurt had sailed more than a decade earlier. Else kept a charming record of this voyage, with observations about the weather, the sights, and their passage through the locks. They had taken along Hilde, who was old enough to be a companion to her grandmother and could be trusted not to launch herself out of the boat at an inconvenient moment. The sailing trip turned out to be bittersweet, as Anna died within a few weeks of returning home; it was the last time they saw her alive.42
Hamburg University
The death of Alfred’s mother in late September 1919 gave a sense of finality to the shift in professional plans and domestic arrangements signaled by the move to Hamburg. Die Hütte was now his no longer; it belonged to Tony. They were (of course) always welcome there, but as guests. Alfred’s home and his work were now in Hamburg. He took up his duties officially on 14 September, becoming the head of the meteorological work of the observatory and in charge of all its official correspondence, which was extensive and burdensome. Two weeks later, on 27 September, he received the expected appointment as instructor in the University of Hamburg, with his subject area defined as “Geophysics, especially Meteorology.”43
Wegener had been excused the necessity of a Habilitationschrift, but he still had to give his inaugural lecture (Antrittsvorlesung). In keeping with his new title and his academic appointment, he elected to give a lecture entitled “Meteorological Problems in Polar Research,” which required little in the way of new preparation and could be expected to be of interest to a broad audience, especially when illustrated amply with lantern slides. He gave his lecture on 11 October, and as there was another lecture scheduled immediately after his—by a recently appointed botanist, Edgar Irmscher (1887–1968)—Alfred and Else decided to stay on, as a courtesy to their new colleague.
As Alfred and Else took their seats in the lecture hall to await the lecture by the young botanist, Else looked up at the front of the room, where an assistant was hanging a series of maps. She elbowed her husband to look at them: they were maps of continental positions in different periods of Earth history, from the standpoint of Wegener’s theory of continental displacements.44 The young botanist, Irmscher, strode to the podium and announced his lecture topic: “The Origin of Continents in Relation to the Diffusion of Plants.”45 The lecture, to Alfred’s intense surprise and pleasure, was a full and detailed defense of the displacement theory as the most reasonable hypothesis for explaining the diffusion and distribution of plants on different continents. Irmscher posed the problem as a contest between the hypothesis of continental permanence, in exactly the form it had been given by Soergel, and Wegener’s hypothesis of continental displacement.
Moving from map to map over the course of an hour, Irmscher explained that the distribution of certain families of vascular plants required unhindered communication, which had previously been explained by the land bridge theory—Irmscher referred to this theory alternately as the Brückentheorie (bridge theory) and Permanenztheorie (permanence theory). He gave a detailed exposition of the bridge theory of Soergel as outlined in the 1917 book in which the latter had repeatedly attacked Wegener. Irmscher went on to assert that whatever the utility of the bridge theory to geologists, it was clearly a geophysical impossibility because of isostasy. Soergel was simply wrong. He concluded, “The acceptance of polar wandering, and the associated displacement of climate zones is, in any case, essential for the understanding of plant diffusion. Of the views that have been put forth concerning our picture of the origin of the largest features of the earth, the displacement theory of Wegener accords better than any of the others with what we know about the distribution of vascular plants. This material [the distribution of plants] may be considered to offer support for this theory.”46
Irmscher had no idea that Wegener was even in Hamburg, let alone that they were prospective colleagues at the same university, and Wegener had no idea that he had garnered support and even allegiance from botanists and plant geographers. Heretofore he had mostly employed paleontological data gathered by men hostile to his own theory, with the sole exception
of Edgar Dacqué, and yet here was a young botanist and paleobotanist willing not just to consider his displacement theory as a reasonable hypothesis but to judge it the sole adequate candidate proposed to date to explain the distribution of vascular plants. Moreover, this support had come from a man who was soon to head the Institute of General Botany at the University of Hamburg and could provide counterweight to Hamburg zoologist Georg Pfeffer’s woolly dismissiveness. The contrast between the botanist and the zoologist confirmed in Wegener’s mind his intuition that a generational shift was necessary for a change in opinion: Pfeffer was sixty-five; Irmscher was thirty-two.
Continental Displacements, 1919–1920
Whether Irmscher’s lecture was the inspiration or simply a spur to drive him on, in the fall of 1919 Wegener decided to proceed with an updated and revised edition of his 1915 book Die Entstehung der Kontinente und Ozeane. As preparation for this revision, he sent to a bookbinder a copy of that book, to be rebound with blank sheets between each pair of printed pages. On these blank pages he meticulously copied out passages from any work that had appeared between 1916 and 1919 which referred to, or had any import for, his displacement theory; these references and sources he placed directly opposite those points in the book to which they referred.47
In the autumn of 1919, now with access to the observatory’s extensive library and periodical collections and to his father-in-law’s personal library of several thousand volumes, Alfred was able to work his way systematically through this material and to think through the comments and criticisms. He recorded (in his newly rebound version of his 1915 book) those emendations that seemed most apposite and addressed those misunderstandings (and errors) that most needed amplification and correction.
More important for this effort than his proximity to the library and reference materials was his proximity to Köppen himself. In 1911, and again in 1915, Wegener had made major changes to a book manuscript after its last review by Köppen; in each case these changes and additions had been magnets for the criticism of his reviewers: from Exner in the case of his 1911 book on thermodynamics, and from Diener, Semper, and Soergel in the case of his book on continents and oceans. Alfred had written to Köppen in late 1915, admitting his disastrous penchant for being deflected by side issues and his inability to keep himself focused on the main line of argument.
In their correspondence in the spring of 1918, Köppen had repeatedly pressed Wegener to explain isostasy, “mass defects,” “negative gravity anomalies,” and other aspects of his geophysical argument. Köppen had indeed at first misunderstood these ideas, but in the main the fault lay not with Köppen’s intellect but with Wegener’s tortured exposition. The proof of this is that on 6 March 1918 Köppen had given a lecture before the Hamburg Natural History Society, on the subject of “Isostasy and the Origin of the Continents.”48 A page-and-a-half summary of this lecture which appeared in the society’s proceedings gave a clearer picture of isostasy, of the difference in gravity over the continents and over the oceans, and of the density difference between the Sal and Sima than Wegener had been able to produce in the first four chapters of his 1915 book.
Köppen, talking to a nonspecialist audience in March 1918, kept it simple and made it clear: the rocks of the continents are less dense than those of the ocean. Somewhere 40–50 kilometers (25–31 miles) below the surface there is a “Lava Sea,” in which the continents, 100 kilometers thick, float. These continents can no more sink further into the material below them than icebergs can sink in the ocean. This is true, he continued, whether one accepts the notion that continents move laterally or the notion that continents are permanent in place. If one wants to believe that former continents were connected by broad land bridges, that is one thing; but to imagine that such continental land bridges can sink when no longer needed is contrary to the known facts.49
Georg Pfeffer was in attendance at the lecture, and one may suspect that Köppen was delivering it as a response to Pfeffer’s lecture in December 1917 attacking Wegener’s hypothesis. Köppen’s lecture drew a strong response from Pfeffer: the secretary of the society noted drily in the minutes of the meeting that “Prof. Pfeffer turned the discussion after the lecture into a long oration against the principles underlying Prof. Wegener’s views, attempting to invalidate them, using facts from the realms of paleontology and the zoogeography.”50
What Pfeffer missed is that Köppen did not defend that theory but merely proposed it as an alternative to the theory of permanent continents and oceans. In fact, in 1918 Köppen was not yet convinced that his son-in-law was correct; what he had finally understood was that the contraction theory in its current form—that is, the Brückentheorie of broad intercontinental connections via now-sunken land bridges—was impossible, and that this impossibility extended to all paleogeographic theories that depended on the existence of such sunken land bridges. It was as if Köppen had grasped for the first time Wegener’s formulation in 1912: extensive evidence exists of former connections between the continents. The geophysical theory (the contraction theory) that explained these former connections and their later interruption (with its sunken land bridges) had been shown to be impossible. Only a few choices were available: reject the paleontology, reject the geophysics, or find a way to reconcile the paleontology and the geophysics. What was not possible was what Diener, Semper, Soergel, and Pfeffer wanted: to make this all go away. That was the sole point of Köppen’s lecture: that everyone who knew anything about geophysics accepted the principle of isostasy; it was not negotiable, and it would not go away.
Köppen completed a revised and expanded version of this lecture in May 1918 and offered it to the Geographische Zeitschrift. In this article he demonstrated that the principle of isostasy was not some geophysical oddity useful to a hypothesis about floating continents, but absolutely essential to understanding the postglacial surfaces of northern Europe and Scandinavia. He showed a map of a postglacial lake running the length of Norway and Sweden, long since vanished but with its shorelines still existing, noting that only the deep depression of the rock by the weight of ice in central Scandinavia could have created a basin large enough to hold this amount of water; the documented uplift of Scandinavia would explain the lake’s disappearance. He also employed Wegener’s map of the reconstructed North Atlantic continent before the separation of North America and Greenland from Europe, showing that Wegener’s calculated pole position allowed the farthest extent of the ice in both North America and Europe to occur exactly on the 60° north latitude circle, which matched the disposition of ice age glacial remains (especially the moraines) in the present.51
Köppen’s choice of a geographical journal was no accident. From the beginning Wegener’s hypothesis had been of most use to geographers, paleontologists, and paleogeographers who could employ it to explain puzzling distributions of plants and animals in the fossil record. While this could be done for most of the history of the Northern Hemisphere merely by moving the pole of Earth, it could not be done for the Southern Hemisphere by pole motions alone. Köppen understood the need to find support where it could be found. Wegener’s original statement of the hypothesis had, after all, been accepted to a geographical journal; Wegener’s early champion Dacqué was a pioneer of paleogeography. Wegener’s initial plan to have the hypothesis tested by telegraphic time signals had been endorsed by senior geodesists and geographers such as Carl Albrecht and Albrecht Penck. Köppen used his article in Geographische Zeitschrift to keep the terms of the argument in front of this audience.
Köppen’s figures showing the extent of a former postglacial lake covering most of Sweden, verified by shorelines, which had disappeared by isostatic uplift (left), and his use of one of Wegener’s figures of a reassembled Northern Hemisphere continent to show how it made sense of the extent of the ice during the Pleistocene glaciations (right). From W[ladimir] Köppen, “Über Isostaise und die Entstehung der Kontinente,” Geographische Zeitschrift 25 (1918); see note 51.
Now, eighteen
months later, Köppen still needed to be convinced, not so much of the scientific plausibility of his son-in-law’s hypothesis, but rather of its accuracy with regard to all classes of existing data. This was an important point. The adequacy of a global hypothesis of any kind must be a compromise between its scope (how many things it gathers within its ambit) and its precision (how many things it can explain in detail). This is particularly difficult in combining the data of geology and paleontology on one hand and the data of geophysics on the other into a hypothesis of the “whole of Earth.”
Once Wegener began the revisions for the second edition, in October 1919, Köppen and Wegener discussed the book almost every day, though the time for this joint work and these conversations was severely limited. Throughout the fall of 1919, Alfred was extremely busy at the Marine Observatory, putting into place the new protocols for gathering weather data. He was also teaching a course at the University of Hamburg that autumn, entitled “Aerology,” aimed at training a new generation of German meteorologists from among the many veterans enrolled.52 The choice of this course was tactical with regard to his time, as the subject matter could best be taught at the kite station near Großborstel, rather than in the city. This saved a few hours of travel each week, but the time pressure was still intense and the commutes long.
The work on continents and oceans was thus restricted to the late afternoon after Alfred returned from the observatory (conversations with Köppen) and the later evening after the children had gone to bed (the actual writing and revision). In spite of Alfred’s desire for a separate workroom, lamp oil was in short supply, and there was only enough for one lamp each evening, and thus no illumination in Alfred’s study while family life was under way in the main room of their lodgings. Once the children were asleep, Else worked at her sewing, sharing the lamplight with Alfred as he worked at his desk, and in this way it was much as it had been in Marburg in the early years of their marriage.53
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