76 



SCIENCE. 



Vol. XXll. No. H9 



was first proposed by Sir John Evans in 1866, has there- 

 fore lately attracted the favorable consideration of some 

 American giacialists, and in Europe has been championed 

 by Nansen in his very interesting work, "The First Cross- 

 ing of Greenland." This theory supposes that within so 

 late a part of the earth's history as the Ice age, the north 

 pole may have moved to the region of southern Green- 

 land and returned, giving in the period of its digression 

 glacial conditions for all the lands adjoining the North 

 Atlantic Ocean, and the same for the antipodal, then south 

 polar, portion of the globe. A small observed variation of 

 latitude, discovered several years ago by German and 

 Kussian astronomers, seemed to give a foundation for this 

 view, but within the past two years the brilliant investi- 

 gations of Dr. S. C. Chandler, showing that these varia- 

 tions are of very small amoujit and in two short periods, 

 one of fourteen and another of twelve months, while no 

 appreciable secular change of latitude can be recognized, 

 leave to us no basis for this theory of the cause of accu- 

 mulation and disappearance of ice-sheets. 



The third theory, which the writer believes to be ap- 

 plicable, sufficient and acceptable for all the observed 

 facts of the Glacial period, attributing the ice-sheets to 

 high altitude of the drift-bearing countries, has also been 

 long under consideration, having been first suggested in 

 1855 by Dana, but failed until recently to receive ade- 

 quate ajspreciation on account of the supposed geologic 

 improbability of sufficiently high uplifts of so extensive 

 portions of the earth's surface. During the past few 

 years, however, this neglected theory has received full at- 

 testation by independent evidence, apart from the facts of 

 giaciation, that these countries, and also other parts of 

 the terrestrial coast, have been, in the same late geologic 

 era which includes the Ice age, raised thousands of feet 

 above their present height, to altitudes doubtless having 

 so cool climate as to bring snowfall during nearly the en- 

 tire 3'ear, the most favorable condition for the formation 

 of ice-sheets. This evidence consists chiefly in the very 

 great dejith found by soundings in fjords and the sub- 

 marine continuations of river valleys, where streams 

 flowed formerly and eroded their valleys, showing these 

 lands to have then stood far higher than now. 



The Hudson Biver channel is traced somewhat more 

 than a hundi'ed miles out to sea, to a maximum depth of 

 2,844 feet. Similar depths are known by the United 

 States Coast Survey and British Admiralty soundings, as 

 Prof. J: W. Spencer has jiointed out, for the former 

 continuation of the Mississippi and St. Lawrence rivers 

 and in the entrance of the Gulf of Maine, between Cajse 

 Cod and Nova Scotia. All about our northern and Ai'ctic 

 shores, from Maine around to Puget Sound, abundant 

 fjords prove the land to have been formerly much ele- 

 vated. On the coast of California, submarine valleys dis- 

 covered by Professor George Davidson, of the U. S. 

 Coast Survey, reach to depths of 2,000 to 3,120 feet; and 

 Professor LeConte has shown that they are of late Ter- 

 tiary and Quaternary age, probably contemporaneous 

 with the submerged valleys of our Atlantic coast, and 

 closely associated with the Glacial i^eriod. In the fluvial 

 deposits of the Mississippi Biver, laid down while the ice- 

 sheet was being formed, Professor E. W. Hilgard finds 

 evidence that the interior of our continent northward, 

 about the sources of the Mississippi, was then uplifted not 

 less than 3,000 feet above its present height. Likewise 

 the fjords of Scotland and its adja^cent island groups, and 

 especially the much deejjer fjords of Scandinavia, prove 

 for that glaciated region an altitude thousands of feet 

 higher than now, the maximum dejjth of the Sogne fjord, 

 the longest in Norway, being stated by Jamieson as 4,080 

 feet. In the same way. New Zealand and Patagonia, for- 

 merly glaciated, are remarkable for their abundant, long 



and branching fjords. But the most surprising known 

 submerged continuation of any river valley is that of the 

 Congo, which, according to Mr. J. Y. Buchanan, is deter- 

 mined, by soundings for a cable to connect commercial 

 stations on the west African coast, to be about eighty 

 miles long, descending to the profound depth of 6,000 feet 

 below the sea level. 



The Congo valley, only about four hundred miles south 

 of the equator, proves that the epeirogenic uplifts, caus- 

 ing giaciation, were not limited to drift-bearing regions. 

 Where the uplifted areas were in so high latitudes, both 

 north and south, that their precipitation of moisture gave 

 snowfall during all, or nearly all, the year, they began to be 

 covered by snow, which became consolidated below into 

 ice and grew in depth to hundreds and thousands of feet. 



Why the earth during the Glacial period was extraor- 

 dinarily deformed for comparatively short periods by 

 great epeirogenic movements of elevation and correlative 

 depression of other tracts, is a more fundamental and not 

 less difficult question, for which I have attempted an an- 

 swer in an appendix of Wright's "Ice Age in North Amer- 

 ica," ascribing these movements to stress stored up previ- 

 ous to its relief by the folding, overthrust and upheaval 

 of mountain ranges. This exjalanation, although diverg- 

 ing widely from formerly assumed conditions of conti- 

 nental stabilitj', seems yet well consistent with Dana's 

 doctrine of the general j)ermanence of the continents and 

 oceanic basins. 



NOTES ON THE DISTRIBUTION OF SOME OF THE 

 CONIFERS OF NORTH-AATESTEBN CANADA. 



BY J. B. TYRKELL, OF THE GEOLOaiCAL SUKVEY OP CANADA.. 



The following observations on the limits of some forest 

 trees were made while conducting geological surveys in 

 the interior of northwestern Canada, in the country ex- 

 tending from Lake Winnipeg northwestward to the 

 Athabasca River. 



White SjDruce (Picea alba) is the most important 

 timber tree of this whole region. It occurs through- 

 out the heavily wooded districts from Riding and 

 Duck Mountains, in northern Manitoba, northwestward'to 

 the great forest region between the Saskatchewan and 

 Churchill rivers, and thence westward beyond the 

 Athabasca. North of the upper part of Churchill Riv- 

 er it extends into the rocky granite country for a short 

 distance and then disappears, so that its general northern 

 limit is here reached at, or south of, the height of land; 

 but while the writer was travelling across Little Hatchet 

 Lake, in north. latitude 58°40 and west longitude 103°45, 

 a high sandy island was found on which was a small grove 

 of tall white spruce, some trees with a diameter of fifteen 

 inches. None others were seen anywhere in the vicinity. 

 This grove, therefore, forms a little outher in the sur- 

 rounding scattered forest of smaU. black spruce and 

 Banksian pine, the hill of warm dry sand furnishing it 

 with a sufiicently congenial home. Extending in from the 

 west the white spiruce occurs on and around the shores of 

 Lake Athabasca, but it does not apjjear to grow at any 

 great distance back from the lake. Black Sj)ruce {Picea 

 nigra) is usually a smaller tree than the last, and is scat- 

 tered on the low lands everywhere thoughout the forest 

 regions of the Province of Manitoba, and the District of 

 Saskatchewan, but north of the Churchill River, and south- 

 east of Lake Athabasca it often ascends to the higher 

 lands. Its northern limit for this region has not yet been 

 traced. Balsam Fir [Ahies balmmea) grows to a large size 

 among the white sjsruce on the toj) and sides of the Duck 

 Mountain in Manitoba, and bet'sveen the Saskatchewan 

 and Churchill rivers in the District of Saskatchewan. It 



