October, 1913. 



KNOWLEDGE. 



385 



or bruised its activity was stimulated, and that it then 

 emitted a much greater quantity of carbon dioxide. 



DUST EXPLOSIONS. — Interesting experiments have 

 been made by Mr. W. R. Lang (Proc. Chem. Soc, 1913, 

 No. 168, 1911) to test the liability to explosion of finely 

 divided starch and coal dust when mixed with air. The fine 

 powder was allowed to fall into the upper end of a vertical 

 glass cylinder about seven feet long by four inches in 

 diameter. Through the sides of this open glass chamber, 

 about half-way down, were fused two wires connected with 

 an induction coil, so that a spark could be passed through the 

 mixture. When this was done the dust, whether of coal, 

 starch or lycopodium, ignited explosively; the combustion 

 spread throughout the length of the tube, and flames issued 

 from each open end. Analogous results were produced by 

 applying a light to the end of the tube. 



Microscopic measurements of the particles of different kinds 

 of dust used in the experiments were made, and the 

 average results calculated into the total areas of the 

 substances per one hundred grammes. In this way the 

 following results were obtained : — 



GEOGRAPHY. 



By A. Stevens, M.A., B.Sc. 



A PHYSIOGRAPHICAL STUDY IN NEW ZEALAND. 

 — In the September Geographical Journal there is an • 

 account of the physiography of the middle Clarence valley, 

 New Zealand, by Mr. C. A. Cotton. The Clarence River 

 rises near Mount Franklin, in North Canterbury, and after 

 flowing in a southerly direction for some forty miles, turns 

 sharply towards the north-west, flows for fifty miles between 

 the Seaward and (Inland) Kaikoura Ranges, and is again 

 sharply deflected to the south. The paper in question dis- 

 cusses the portion of the course which lies between the 

 Kaikouras. 



The geology of the country has not been fully worked out' 

 and, as so frequently happens in New Zealand, presents some 

 difficult and disputed questions. Generally it may be stated 

 that the underlying older rocks are of about Carboniferous 

 age. They are much contorted, and the system of folding 

 has not been described. These rocks have been extensively 

 denuded, and probably were cut down so as to present a 

 surface of low relief. Newer deposits, of age ranging from 

 Cretaceous to Pliocene, covered them; on a basal con- 

 glomerate rested soft mudstones, and the sequence passed up, 

 through resistent beds of limestone and flint and soft marls, 

 to a top layer of hard conglomerate. Earth -movements on a 

 large scale have affected the area and produced two huge 

 anticlines, or probably anticlinoria, separated by an 

 asymmetrical syncline, the north-west limb of which gave 

 way, and is represented by a reversed fault of enormous and 

 undetermined throw. The anticlines build the Kaikoura 

 Ranges, while the syncline has been occupied by the Clarence 

 River, which in its middle course is therefore a consequent 

 stream. 



In the cycle of denudation which ensued, the covering of 

 newer rocks was removed from the mountains by the streams 



of the Clarence system, a flat floor of mudstone being left in 

 the valley. This lies closer to the north-west side of the 

 valley, where it is faced by the scarp of the limestone, and the 

 want of symmetry of the valley is a direct consequence of 

 the asymmetry of the syncline. A subordinate uplift follow- 

 ing rejuvenated the stream, already at base level, and it 

 proceeded to cut a gorge in the valley floor. The courses of 

 rivers further to the north and to the south are transverse to the 

 middle Clarence, and consequently to the axis of the 

 mountains, and these, Mr. Cotton considers, are antecedents, 

 whose courses were determined by a simple regional uplift 

 earlier than the folding. By the latter movement the 

 Clarence alone was diverted, and only in its middle course, 

 where the rise of the land reached its maximum. The lower 

 Clarence follows the course of an antecedent stream. The 

 valley slopes and floor of the middle Clarence are trenched 

 by streams antecedent, consequent, and subsequent, some 

 graded, some still cutting. The limestone ridge is dissected 

 by superposed consequents from the Kaikoura Range which 

 often join twos or threes just before clearing the ridge, and so 

 cut out pyramidal hills of limestone rather lower than the 

 adjacent part of the scarp. The fault-plane gives rise in 

 places to noticeable topographical features. It facets spurs 

 from the Kaikouras (long spurs from the Seaward Kaikouras 

 are also faceted — but by the stream), while in the lower part 

 of the valley it is marked by a bench, some twenty feet wide, 

 which represents an earthquake fissure. Evidences of 

 glaciation are wanting in the area, though it has been held 

 that the valley is deeply ice-worn. Mr. Cotton believes that 

 glaciers have always been absent, as they are now, for the 

 steepness of the slopes prevents the accumulation of reservoirs 

 of snow. 



OCEANOGRAPHY OF THE MEDITERRANEAN.— An 

 article in Nature, for September 4th, draws attention to the 

 report of the Danish Oceanographical Expeditions of 1908-10, 

 to the Mediterranean and the adjacent seas. It is found that 

 the Mediterranean is divided into two basins by a submarine 

 ridge four hundred metres below sea-level at the deepest 

 points, which continues the line of Italy and Sicily to the 

 north coast of Africa. Of these basins the western is, for the 

 most part, two thousand to three thousand metres deep, the 

 eastern generally deeper, soundings of more than four 

 thousand metres having been made. The main interest 

 centres in the movements of the water. The rainfall balances 

 less than one quarter of the loss by evaporation, and the 

 water-level is maintained by an inward current from the 

 Atlantic which runs from one to three knots. As a direct 

 consequence the pressure inside is increased, and a stream 

 sets out towards the ocean at a speed which varies between 

 one half and five knots. Although the temperature is uniformly 

 so high as thirteen degrees at the depth of one thousand 

 metres, the unusual salinity, due to excessive evaporation, 

 raises the density of the water so much that the outgoing 

 current is a deep one. These currents are, of course, affected 

 by the tides, and the warm outward current is made by the 

 rotation of the earth to swing to the north and east in the 

 lower strata of the Atlantic. This may explain the occasional 

 high salinity in enclosed seas on the British coasts. Again, 

 the high precipitation in the area which feeds the Black Sea 

 and the Sea of Marmora makes these waters remarkably poor 

 in salts, and conditions exactly opposite obtain. But the 

 threshold of the Black Sea is so shallow that the deeper layers 

 of the water are stagnant, and the dissolved gas is hydrogen 

 sulphide ; hence only some forms of bacteria people the sea. 

 The water-circulation within the Mediterranean is complex 

 and incompletely described. It varies at different depths and 

 in different areas. 



STUDIES IN GLACIERS.— From data, more or less 

 complete, covering a period of some dozen years, one might 

 conclude that at present there is a general tendency to retreat 

 of the ice-fronts of the glaciers of the world. From several 

 parts reports come in of the extension of the length of 

 glaciers, but the figures require careful scrutiny (Hans Hess, 

 Petermanns Mittcilungen, April), and when circumstances 



