July 29, 1897] 



NA TURE 



303 



line as far as the Lena, then spread southward into the Amur 

 Valley ; it thus reached the sea of Okhotsh, whence one coast 

 ran southward across Japan, and the other eastward to Alaska. 

 From many Arctic localities these Triassic rocks are rich in 

 fossils ; but the fauna of the Triassic Arctic Ocean is so different 

 from that of the contemporary Mediterranean Sea, that it is 

 doubtful whether there was any direct connection between them. 



After the close of the Trias there is a considerable gap in 

 the annals of the Arctic Ocean. When the record is resumed 

 in the middle and upper parts of the Jurassic period, we 

 find that the sea has either again grown very considerably, or 

 has materially shifted its position. Thus the sea, instead of 

 ending near Spitsbergen, has encroached to Greenland on the 

 west, and extended southward to the Lofoten Islands, to southern 

 Sweden and to England, France and Germany; and further east 

 I series of gulfs ran southward up the valleys of the Pelchora, 

 Obi, Venesei, and the Lena. The Jurassic Arctic Ocean, there- 

 fore, appears to have been connected with whatever sea there 

 may then have been in the North Atlantic ; but, unlike its 

 Triassic predecessor, it was separated from the Pacific by a 

 broad belt of land. 



In the succeeding Cretaceous period we get the last geological 

 proof of an Arctic Ocean before that of the existing period. 

 The sea had receded in the Old World, but it had gained con- 



seas by the elevation and depression of parts of the bands of 

 sediments, which surround the Archean blocks. The blocks 

 themselves are of great geological antiquity, and the successive 

 earth movements have been moulded upon them. As the main 

 nuclei of the great land masses of the Arctic regions are there- 

 fore of vast antiquity, it may be thought only reasonable to 

 assume an equally great age for the central ocean basin. But 

 if we look at a map of the Polar regions showing the strike of 

 the rocks and the trend of the mountain chains, we see that these 

 all run north and south, and end abruptly on the margin of the 

 Polar Basin. This meridianal trend occurs in the branch of 

 the Rocky Mountains that forms the western boundary of the 

 Mackenzie River, in the Archean axes of Boothia and Melville 

 Peninsula, in the strike of the rocks of Northern Greenland and 

 Western Spitzbergen. In Asia it is particularly well shown by 

 the Ural and Verkhanoysk Mountains and their respective 

 geological continuations, Nova Zemlya and the New Siberian 

 Islands, and by the parallel chains between the Lena and 

 Behring Straits. 



Analogy with similar truncated mountain lines elsewhere 

 renders it probable that all the mountain ranges, having what 

 von Tol calls a "Ural orientation," once extended further to 

 the north. If they did so, they would have effectually broken 

 up the existing Polar Basin. At the present time our know- 

 ledge is insufficient for a final conclusion. 

 But the evidence of the historical geology, 

 physical structure and earth movements of 

 Arctic lands are all consistent with the 

 origin of the Arctic Basin as a great arqa 

 of subsidence (a " senkungsfeld " of Suess) 

 later than the deposition of the lower 

 Tertiary plant beds. The geological facts 

 attest such great geographical changes in 

 that region, that geologists are not at pre- 

 sent bound to abandon helpful explana- 

 tions, which are in themselves probable 

 and are in harmony with the geological 

 evidence, simply because they may be 

 inconsistent with the permanence of the 

 Arctic Basin. J. W. Gregory. 



^=U 



Fig. V— The Northern Seas in the Trias (cross-hatched) and Upper Jurassic (lined tint). 

 [In Eastern Asia, the lined area should not come south of the broken line in !at. 75°.] 



SCIENTIFIC INVESTIGA TIONS 

 OF THE SCOTTISH FISHER V 

 BOARD. 



'T'HE third part of the Fifteenth Annual 

 -*• Report of the Fishery Board for 

 Scotland, dealing with the principal 

 scientific investigations conducted under 

 the auspices of the Board in 1896, has just 

 been published. The work done may be 

 judged from the subjoined summary, 

 which is abridged from the general 

 statement prefixed to the detailed reports 

 on the investigations carried out. 



siderably in America; for marine Cretaceous deposits occur in 

 Central British North America, and the sea seems to have 

 entered that area by the Mackenzie River depression. In the 

 Tertiary era ail the positive evidence relates to land conditions, 

 excepting some obscure fossils in one or two localities, and some 

 patches of Miocene shell-beds bordering the Pacific, as on the 

 shores of the sea of Okhotsh. The Arctic Ocean therefore 

 appears to have shrunk very considerably, and the land areas to 

 have once again broken up the basin of the northern sea. 



.A general summary, therefore, of the facts of Arctic geology 

 show that the Arctic Ocean has varied greatly, both in position 

 and size. The Arctic Basin is at the present time bounded by 

 a rim of land which is supported by five great blocks of Archean 

 rocks; these blocks form, respectively, Scandinavia and North- 

 western Russia ; Labrador and North-eastern British America ; 

 Greenland ; Alaska and North-eastern A.sia ; and the Archean 

 block of Central Siberia. These Archean blocks were each 

 more or less completely surrounded by bands of sedimentary 

 rocks. At least two of them have never been below sea-level ; 

 and there is no satisfactory evidence to prove that the other 

 blocks have been submerged, at least, since Middle Paleozoic 

 times. In fact, the geological history of the Arctic Basin is the 

 record of the alternate enlargement and diminution of the Arctic 



NO. 1448, VOL. 56] 



In the course of the year, the investigations which were carried 

 on under the supervision of the Scientific Superintendent, Dr. 

 Wemyss Fulton, were prosecuted on the same general lines as 

 in previous years, and have resulted in further extensions of 

 knowledge respecting the life-history and habits of the food 

 fishes, and by the physical conditions and changes in the sea 

 which bear upon fishery problems. Special attention was 

 given to certain hydrographical questions concerning the cir- 

 culation of the water in the North Sea and the adjacent parts of 

 the North Atlantic. In addition to such inquiries, the hatching 

 and artificial propagation of some of the important food fishes 

 have been continued at the Board's Marine Hatchery at 

 Dunbar. 



One of the most important results of the work has been to 

 show that the food fishes which form the basis of the fishing 

 industry — such as plaice, cod, haddock, ling, turbot, &c. — do 

 not spawn on the east coast within the three-mile limit, as was 

 previously supposed. On the other hand, it is not known at 

 what distances from the shore or in what precise localities the 

 spawning areas are chiefly situated. It would obviously be of 

 great advantage to obtain accurate information on this subject, 

 and to be able to map out on a chart the regions where the 

 various species of the food fishes spawn. 



