Imágenes de páginas
PDF
EPUB

INTRODUCTORY CHAPTER.

37

and Spitzbergen at a somewhat later period, represented by the mountain limestone. Further research will probably indicate its occurrence in other northern countries. The bearing which these facts have on climate is thus expressed by Professor Heer: “Moreover the climate of Bear Island must have been as favourable to the growth of plants as that of Ireland or the Vosges, although that island lies 26° farther north ; for the corresponding species are as large and quite as luxuriantly developed, and have even produced more considerable coal strata than those of lower latitudes in the same period. Warmth, therefore, must at that time have been more equally distributed over the earth, whilst already in the Miocene time a great difference had begun to arise, which has increased immensely up to the present time. The climate must have been not only more equable but warmer, as is shown by the coral banks which were formed at that time in Spitzbergen, as well as by the enormous tree-like cryptogams, and the large-leaved ferns which Bear Island produced.” In Greenland fossil plants belonging to several periods have been discovered. Those from Angiarsuit and Kassok are very old, but the age has not been determined. They however seem to be similar in character with those from the lower cretaceous beds at -Korne. At this place these beds represent terrestrial conditions, there being an entire absence of marine fossils. This flora is characterized by numerous ferns, especially Gleicheniæ; by a remarkable cycad (Zamites archea); by numerous conifers, belonging to the genera Pinus, Sequoia, &c.; and by the absence of dicotyledons. The upper cretaceous beds are developed between Atanekerdluk and Atane. They comprise thick strata of coal, and the fossils are terrestrial ; the marine being absent. The flora comprise cycads, ferns in abundance, Sequoia, and numerous dicotyledonous leaves. The great bulk of the strata on and around Disco Island are of Miocene age. Plants have been collected from three distinct horizons representing periods separated by considerable intervals of time. The lowest horizon occurs at Atanekerdluk. The beds are remarkably rich in impressions of plants, and in carbonized trunks of trees. These trunks are in places so abundant that the Greenlanders collect them for fuel. The second horizon contains beds of coal, and impressions of leaves, cones, seeds, &c., as also carbonized and silicified tree-stems at Netluarsuk, Ifsorisok, and Assakak. At Sinnifik and at Perilosok an upper Miocene flora occurs, represented by fragments belonging to such trees as Salix Platanus, Cratægus, Sequoia, Taxiles, and Populus.

INTRODUCTORY CHAPTER.

These localities are on or near 70° N. Spitzbergen also has yielded a rich Miocene flora. These floras indicate a climate as warm as the temperate, or perhaps even the temperate parts of Europe at the present time. Professor Heer believes that extensive forests were spread over all the North Polar lands during the Miocene period. Dr. Hooker infers from the present remarkable distribution of the Arctic plants that they migrated across the Polar region at a time when the warmth was much greater than now. An examination of the plants of the Polar lands, discovered and undiscovered, present and past, would enable botanists to found their conclusions on a broader and safer basis than they can now. The work that has already been done * is a strong inducement to continue the research and render this region one of the most interesting and instructive in the world.

Another branch of science which would be greatly advanced by Polar research is terrestrial magnetism. The magnetic needle, as is well known, points to the magnetic North, or Pole, which Pole lies considerably to the south of the earth's Pole. In 1830 Sir James Ross discovered it in 70° 5' 17" N., and 96° 46' 45". It is also constantly shifting its position from E. to W. and from W. to E., within certain limits, and

* See list of miocene flora and fauna given in the body of the present work.

O

probably on or near the same parallel of latitude. In 1663 it was due north of Paris : it then advanced westwardly till about 1819, when it returned eastwardly, in which direction it is still moving, and Bond supposes that the eastern limit will be reached in about 2140. There are so many resemblances and analogies between the secular and local distribution of the elements of terrestrial magnetism and heat that many persons are convinced that there is an intimate connection between them. The magnetic Pole lies near the region of greatest mean cold, and its course appears to be along the zone of lowest mean temperature. Auroras are believed to be essentially the results of magnetic disturbance, and originate, or at any rate are most abundant and energetic along a zone situated on and near the latitude of the magnetic Pole, which is probably that of greatest cold. It is inferred that no auroras are produced north of about 80°; in other words, that a person at the Pole would see the auroras on the southern sky. The alternate heating and cooling of the Polar area, together with the great difference of temperature between the zone of greatest cold and the tropic of the northern hemisphere, would seem an adequate and probable cause for the generation of magnetic currents and storms. The auroras are observed to occur in cycles of varying

INTRODUCTORY CHAPTER.

intensity and frequency, lasting about eleven years ; and these variations seem to coincide with the variations in the number and importance of the spots on the sun, which also run through cycles of about eleven years. According to Mr. Meldrum the cyclones of the Indian Ocean also occur in eleven yearly cycles, during which their frequency and strength coincide with the condition of the solar spots. He also infers, from a careful examination of the meteorological reports of various places, that in the countries surrounding the Indian Ocean, such as Ceylon, Mauritius, Adelaide, &c., the rainfall periodicity corresponds with the cyclone periodicity; and that the years of maximum rainfall correspond with the years of maximum sun-spot frequency, while the years of minimum sun-spot frequency are those of minimum rainfall. These remarks suggest that the observation of the climatic and telluro-magnetic elements in Polar regions would lead to results of the highest scientific importance, which would also be of great practical benefit. This object alone should be a sufficient answer to those who want to know what use there may be in Polar research. The scientific man knows that no well-conducted inquiry is useless; and that the electric telegraph, the steam-engine, the galvanic battery, and numerous other inventions of unques

« AnteriorContinuar »