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recession of the earth from the sun, while in autumn the decline is in part counterbalanced by the earth approaching the sun. This would help to raise the autumn temperature. If the northern summer occurred when the earth was nearest the sun, the circumpolar area, it is believed, would be heated more strongly than it is now. The intensity of the heat might be still further increased by another modification of conditions. The present eccentricity of the earth's orbit is slight compared to what it has been in past times. At present the earth is 3,000,000 miles less than the mean distance nearer the sun in aphelion than in perihelion ; but at certain periods it has been 14,500,000 miles less than the mean nearer the sun in aphelion than in perihelion. In other words the earth when nearest the sun is now about 88,400,000 miles from the sun ; but during past epochs it has approached to within about 77,000,000 miles. The intensity of the heat is in inverse proportion to the square of the distance : so that if the Arctic Pole were exposed to this greater heat during summer, the temperature, other conditions remaining the same, would be proportionately increased. There is yet a third modifying cause which would tend to intensify the heat. The obliquity of the ecliptic is now 23° 28'; but astronomers admit that it may have been at times as much as 30°. This would imply a more extensive Arctic circle, and a higher, therefore a hotter, sun during the midsummer months. It is possible to conceive a time when the Polar regions were under the most favourable conditions as regards heat-a time when the earth was at its nearest to the sun in midsummer when the Polar region contained little or no land, and when the sun rose high in the heavens, shining for weeks or even months with noon-day power. At present the conditions are for the most part not the most favourable for warming the North Pole ; and the fact that it is less ice-encumbered than the South Pole probably arises from there being, as is supposed, little land near it. The conjectures above given as to what may have been are rendered probabilities by the character of the fossil plants which have been discovered in high latitudes. On Bear Island has been found the earliest rich land flora as yet known. Its age is assigned to the beginning of the Carboniferous epoch, or the later portion of the Devonian epoch. This flora comprises species of Calamites, Lepidodendron, Cyclostigma, and many ferns. The individual specimens are exceedingly abundant. The flora has been traced from 47° to 76° N. A flora of a somewhat similar character occurred in Parry Island
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, T'axiles, and Populus.
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.