Ill 



KNOWLEDGE. 



April, 1915. 



meandering, and two meandei are laterally cutting towards 

 each other, thej have not yet joined on the surface, 



the intervening rock, which is limestone, has been undercut 



b .in i mi ut ili.it .1 tunnel has been formed from t ho 



mi. mi to the other. In the third case, the junction 



oi two stn n moved one and three-quarter 



miles upstream 1>\ intercision, due to the cutting through 



"( .1 ridge of chert winch formerly eparated two meanders. 



SHAl'l I'l Mil \M\KtTIi i oXTINENT.— Prob- 

 ably the most discussed point in Antarctic physiography has 

 been the que tion as to whether there is one continent or 

 two; that is, whethei there is a continuous range from 

 Graham land to South \ ictoria Land, or whether, as sug- 



I by Mawson, Graham Land is united to King Edward 

 \ II I and, and separated by a faulted trough or rift valley 



\ ii toria Land. The evidence has been discussed by 

 i .i lllith . Taylor (Gcog. Join .. ( fctobei , November, December, 

 1914), who reviews both the geological and physiographic 

 data. The rocks of Prince Leopold Land arc like those of 

 South Victoria Land. Further, a comparison with the 

 Australian coastal type points to the conclusion that the 

 West Antarctic cordillera continues to King Edward VII 

 I ind, with an intermediate broad belt of lowland — the 

 ner— corresponding to the Tasman Sea between 

 Australia and New Zealand. Another point in favour of 

 tins idea is that the Victoria Land mountains belong to the 

 " Atlantic. " or " subsidence " type, whereas Graham Land 

 belongs to the " Pacific " type, which may be continued 

 from the Andes by the South Georgian loop. The Royal 

 Society Range is probably caused by a late Tertiary- fault, 

 while the foothills seem to be a typical " Scnkungsfeld " 

 area. 



ANTARCTIC GLACIER TYPES.— In the same paper 

 an elaborate account is given oi the ice-fields of the Antarctic 

 continent. Several types of glacier occur in close juxta- 

 position. Of those with large alimentation the great ice- 

 i i p. which is between two thousand and three thousand 

 ei I thick, has been shown to have but little movement. 

 There are several piedmonts, the largest being the Wilson 

 and Putter Point glaciers, which are probably residual 

 from a former glaciation. There are also the large outlet 

 glaciers and numerous small col and dendritic or tributary 

 ones. All the forms of glacial action are well shown by one 

 or other of these types. Thus, the action of the ice-cap 

 and of the piedmont lobes is mainly protective. Glacial 

 erosion, as commonly understood, is evidenced by the 

 outlet glaciers, while " sapping " action, or cirque erosion, 

 generally occurs on the steep slopes of the Royal Society 

 range. An account is also given of the various stages of 

 cirque formation and of glacial deposition. One interesting 

 deduction is that the present conditions in South Antarctica 

 are very unfavourable for glacier erosion, as well as for 

 cirque erosion, which requires rapid alternations of freezing 

 and thawing. 



THE GULF STREAM. — In the same journal, Commander 

 Hepworth discusses the origin and course of the Gulf Stream. 

 Most ocean currents have a close connection with atmo- 

 spheric currents, though the Earth's rotation is also a power- 

 ful factor. The north-east and south-east trade winds give 

 rise to a drift current, which develops into the north and 

 south equatorial currents. The Gulf Stream is primarily 

 due to components of those which find their way into the 

 Caribbean Sea; thence past Yucatan into the Gulf of 

 Mexico, and finally through the Gulf of Florida. The other 

 hypotheses as to its origin, based on temperature differences, 

 on the silt brought by the Mississippi, and so on, are shown 

 (o be untenable. One interesting fact is the daily and 

 monthly variation in the velocity, which has been correlated 

 with the variation in the heights of the tides. While it has 

 been maintained that the Gulf Stream disappears when it 

 comes into contact with the Labrador current, it is more 



probable that it can be traced as far north-cast as Spitz- 

 bergen and the Barents Sea. This is borne out by the 

 evidence of the plankton and also by the occurrence, in 

 these regions, oi warm water oi high salinity, such as is 

 typically found in the Cull Stream. The results of a series 

 of investigations of the relations between sea temperature 

 and air temperature, extending over the last ten years, 

 indicate that no important temperature changes have 

 occurred in the North Atlantic within historical times. 



GEOLOGY. 



By G. W. Tyrrlll, A.R.C.Sc, F.G.S. 



THE ORIGIN OF THE BRIGHT AND DULL 

 LAMINAE OF COAL.— In the December number of The 

 Journal of Geology Mr. T. E. Savage discusses the origin 

 of the bright and dull laminae which make up the mass of 

 an ordinary coal, with especial reference to the coals of 

 Illinois. Any theory of origin has to explain the extreme 

 regularity and wide horizontal extent of these laminae 

 (over several hundred square miles in Illinois) ; the alter- 

 nation of the bright and dull layers ; the predominance of 

 mineral charcoal and of plant spores in the dull laminae ; 

 and the numerous pinnae and pinnules of ferns in the midst 

 of mineral charcoal fragments. Mr. Savage's views on the 

 accumulation of coal-beds may be summarised as follows : 

 (1) The vegetable accumulation began in very shallow 

 swamps. (2) That, as the swamps deepened gradually, the 

 accumulation kept pace with the increasing depth. (3) In 

 oft-recurring cycles of drought, successive levels of the 

 vegetable mass were exposed to the air, and were so modified 

 by partial atmospheric decay as to result in the formation 

 of the dull laminae with their mineral charcoal. The bright 

 laminae would thus be formed by decomposition out of 

 contact with air. Quoting Mr. Savage in the above- 

 mentioned paper : " The dull laminae and mineral charcoal 

 partings of the coal-beds are the records of repeated inter- 

 ruptions of accumulation, during which the surface of the 

 vegetable material in the swamp was above water and 

 exposed to atmospheric decay, resulting in the destruction 

 of the softer parts of the plant tissues, leaving them in an 

 indurated and more or less skeletonised and fibrous con- 

 dition. On resubmergence these residual portions of the 

 vegetable materials were not so readily impregnated with 

 the fundamental matter of the bog as were those parts of 

 the mass that had not suffered partial atmospheric decay, 

 and hence are of dull appearance. Such periods of arrested 

 accumulation of the plant material, due to the exposure of 

 the surface of the vegetable matter of the bog, would be 

 favourable for the accumulation on such a surface of a 

 relatively larger proportion of spores than would be mingled 

 with the vegetable mass during periods of submergence and 

 of normal vegetable growth in the bog, and the resistant 

 nature of the spore cases would permit their better pre- 

 servation than the ordinary plant tissues during such times 

 of exposure. These conditions would explain the greater 

 abundance of spores in the dull than in the bright laminae 

 of the coal-beds. The variation in thickness of the dull 

 laminae would be due to the unevenness of the surface 

 of the exposed vegetable matter in the bog." These con- 

 ditions also explain the alternation of the bright and dull 

 layers, and their wide extent, since they were coterminous 

 with the boundaries of the swamp itself. 



METEOROLOGY. 



By William Marriott, F.R.Met.Soc. 



THE WEATHER OF APRIL— Although April is the 

 mid-spring month, when some warm and genial weather 

 may reasonably be expected, yet there is perhaps no other 

 month in which we are exposed to such great and sudden 

 changes of temperature. The increasing power of the sun's 

 rays and drying north-easterly winds cause excessive 

 evaporation. Some days may be warm and genial, while. 



