February 13, 1891.] 



SCIENCE. 



93 



SCIENTIFIC RESULTS OF HANSEN'S JOURNEY ACROSS 

 GREENLAND. 



Dk. Feidtjof Nansen, at a meeting of the Geographical 

 Society of Berlin, Nov. 8, 1890, read a paper on his journey across 

 Greenland, with special reference to the scientific results of the 

 same. By this expedition it is shown (" Pi-oceedings of the Royal 

 Geographical Society," London) that the whole of Greenland south 

 of about 75'^ north latitude is covered by an immense unbroken 

 coating of inland ice. How far this covering extends over northern 

 Greenlaud is not yet accurately known. That it must go beyond 75° 

 is evident from the mighty glaciers which project into the sea along 

 the whole of the west coast of Greenland. Of these, the immense 

 glacier at Upernivik shows a movement of as much as 99 feet in 

 24 houi-s. Such glaciers must of necessity be fed by an unbroken 

 ice-covei'ing in the interior, because otherwise they would not 

 have sufficient material for their enormous production. Although 

 under 80° north latitude there are large glaciers, like the Hum- 

 boldt glacier, still the latter appears to have no important motion; 

 and, inasmuch as Grinnell Land also is not completely covered 

 with ice, it is quite possible that the extreme north of Greenland, 

 in consequence of the atmospheric precipitation being too insig- 

 nificant, is no longer wholly overlaid with this ice-covering. 



The highest point reached by the expedition exceeded 8,915 

 feet, and lies about 112 miles from the east coast and 168 miles 

 from the west coast. But the highest part of the ice does not lie 

 so near to the east coast as might appear from the foregoing: for", 

 in the first place, the route of the expedition was not at right 

 angles to the coast, but inclined to the longitudinal axis of the 

 country, the direction being first north-west and then west-south- 

 west ; and, secondly, the land in the interior rises from the south 

 to the north. Consequently the highest point of the ice lies, in 

 fact, nearer the middle of the country than would appear from 

 the route. The periphery of the ice-covering corresponds pretty 

 much to the segment of a circle of about (5,450 miles diameter. 

 The Jensen journey into the interior gives a circulaf periphery 

 with a radius of 5,560 miles; and Nordenski old's jom'ney, one 

 with a radius of 14,530 miles. It follows that the upper side of 

 the inland ice forms a remarkably regular cylindrical surface 

 from one coast to the other, although the radii of this cylinder 

 increase considerably from south to north. The underlying land 

 is certainly, as the numerous fiords prove, just as mountainous as 

 Norway. But the fact that the stirface of the ice is so regular is 

 due to the pressure of the plastic ice-masses, and the surface of 

 the ice reaches its highest level just where the resistance to this 

 force is greatest. The watershed of the underlying land lies 

 nearer to the east coast than to the west ; then the resistance to 

 the pressure of the masses of ice will also be greater on this side 

 than on the west coast, and the high ridges of the ice-covering 

 wiU also be found to lie between the middle axis of Greenland 

 and the water-divide of the land buried beneath the ice. 



The thickness of the Greenland ice, Nansen estimates at from 

 5,000 to 6,000 feet over the valleys of the underlying land. The 

 pressure of a glacier 6,000 feet high upon its base would amount 

 to at least 160 atmospheres : the ice-masses must therefore exercise 

 a strong moulding influence uijon the land. The inland ice at a 

 short distance from the coast is composed of fine dry snow, on 

 the top of which the sun in summer only is powerful enough to 

 form a thin melting crust. The ice-poles six feet long could be 

 driven into these masses without striking firm ice. 



The daily variation in the temperature amounted, in the month 

 of September, to from 36'^ to 45*^ F. The annual variation must 

 be enormous. The moisture of the air is very great : with few 

 exceptions, it amounted to between 90 and 100 per cent. The 

 number of days of atmospheric precipitation is also large. Of the 

 forty days occupied by the expedition in crossing the ice, four 

 were rainy, snow fell on eleven, and hail on one. Inasmuch as 

 there is now no melting of the ice in the interior of Greenland, 

 and evaporation also is almost niJ, the chief factor in preventing 

 the further increase of the ice-masses, apart from the great part 

 which is played by the movement of the ice-masses in the direc- 

 tion of the coast, is apparently to be found in the " terrestrial 

 heat."^ Given^the mean annual temperature on the surface of the 



inland ice at —22 F. , and the geo-thermic scale of depth of the 

 ice at about 55i feet per 1° F., the temperature of the ice would, 

 even at 3,000 feet, stand at melting-point. In any case, an active 

 melting process goes on at the bottom of the ice, and rivers pour 

 forth into the sea from under the ice in winter as well as in sum- 

 mer. Nansen himself had the opportunity of observing this 

 during the most rigorous vrinter. These streams, which must flow 

 under the enormous pressure of the ice-masses, are powerful 

 eroding agents. The formation of the " asar " in Sweden, and of 

 the "kames" in Scotland, England, and Ireland, are apparently 

 to be accounted for in this way. 



LETTERS TO THE EDITOR. 

 *** Correspondents are requested to be as brief as possible. Tlte writer^s name 

 is in all cases required as proof of good faith. 



The editor loill be glad to publish any queries consonant with the character 

 of the journal. 



On request, twenty copies of the number containing his communication mill 

 be furnished free to any correspondent. 



What caused the Obliquity of the Ecliptic. 



It is difficult to bring the mind to believe that there ever was a 

 time when there were no seasons, — spring, summer, autumn, and 

 winter, — as now. In attempting to account for natural phenom- 

 ena, we have nearly always assumed that the axis of the earth 

 was orignally inclined to the plane of the ecliptic at an angle of 

 23J°, as we now find it, and of course we in consequence have 

 formed in our minds the idea of the annual recurrence of the 

 seasons through all geological time; hut the elimination of the 

 seasons from the early history of the earth has been forced upon 

 us by the accumulation of facts from the geological record. 

 There is abundant evidence to prove the existence of tropical or 

 sub-tropical animals and plants in Arctic latitudes as late as the 

 tertiary. In Professor Dana's " Manual of Geology " (third edi- 

 tion, p. 352) that author says, "If we draw any conclusion from 

 the facts, it must be that the temperature of the Arctic zone dif- 

 fered little from that of Europe and America. Through the 

 whole hemisphere, and we may say world, there was a genial at- 

 mosphere for one uniform type of vegetables, and there were 

 genial waters for corals and brachiopods." Scarcely any one 

 now, who is conversant with the facts, will deny that the early 

 history of the earth was marked with a uniform, or nearly uni- 

 form, temperature, in all latitudes, prior to and including most 

 of the tertiary. The main difference of opinion existing now 

 among scientific men is how to account for such uniform, world 

 climate. 



So of the glacial period. Every one admits that the great array 

 of facts justifies the conclusion that the poles of the earth were, 

 since the tertiary, covered with great ice caps or sheets several 

 thousand feet thick, and reaching down to the 40th parallel of 

 latitude, constituting the great glacial epoch. There is a wide 

 divergence of opinion, hovvever, as to the origin or cause of this 

 glacial cold. Mr. Croll, in his " Climate and Time," has formu- 

 lated a theory, derived from the secular changes in the eccen- 

 tricity of the earth's orbit, through which he finds a place for the 

 glacial period; but this theory, if true, must provide for alterna- 

 tion of warm and cold periods at the poles throughout all 

 geological time. Professor James Geikie of Scotland, in his 

 " Great Ice Age," indorses this theory, and attempts to find evi- 

 dences of former glacial action, not only in the tertiary, but also 

 in mesozoic and paleozoic times. But the weight of the evidence 

 seems to be against this theory, and Mr. Geikie himself admits 

 that much of his " evidence" is " not very convincing." 



The best and most satisfactory explanation of the warm and 

 cold periods at the poles has been made by Professor C. B. War- 

 ring, in a paper read by him before the New York Academy of 

 Science, and published in the Poindar Science Monthly for July, 

 1886. This paper merits a much more extended notice than it 

 has apparently received, for its author has very strongly fortified 

 his several propositions. Briefly, his argument is this: The exist- 

 ence of tropical vegetables in Arctic latitudes cannot be supported 

 upon the theory of a warm temperature only. Light was as 

 necessary as heat; and this light must [also have been |imiform 



