Mat 25, 1883.] 



SCIENCE. 



465 



rite, and associated with proustite, argentite, native 

 silver, and other minerals. — {Col. sclent, soc; meet- 

 iwj April 2. ) [935 



PHYSICAL GEOGRAPHY. 

 Ocean currents south of Africa. — On the charts 

 publlslied by the London meteorological office (1882) 

 the following currents are shown at the meeting of 

 the Antarctic, Atlantic, and Indian oceans : first, the 

 Agulhas current, moving south-west along the eastern 

 coast of Africa, with a velocity of 51 knots a day in 

 summer (December to February), 46 in winter, and a 

 maximum of 108. It is 4-5° C. warmer than neigh- 

 boring water of the same latitude, and in summer 

 carries a temperature of 25° C. to lat. 35°, and 21° to 

 lat. 39°. As the water in Table Bay is miich colder, 

 it would seem that this current does not enter the 

 Atlantic, except temporarily, in summer time, but, 

 on meeting the Antarctic current about lat. 40°, long. 

 23° E., is turned back to the Indian Ocean in a 

 north-easterly direction. That this is not a simple 

 continuation of the Antarctic current is shown by its 

 warmtli, as well as by the rapid changes of tempera- 

 ture and the alternation of warm and cold bands 

 about lat. 40°. Second, the Antarctic current south 

 of lat. 40°, moving north-east or north-north-east. 

 This is rather independent of the prevailing winds, 

 which follow the parallels closely. As its strength and 

 northward deflection are greatest, and its temperature 

 and density are least, in summer, it is thought to be 

 strongly influenced by the melting of Antarctic ice. 

 West of long. 20° it gives off branches that flow north, 

 along the west coast of Africa. — [Ann. der hydrogr., 

 1SS3, 1, 63.) 



At least the occasional passage of the Agulhas cur- 

 rent into the Atlantic is shown by the drifting of a 

 bottle thrown overboard off the coast of Natal (lat. 

 29° 24' S., long. 33° E.) Dec. 7, 1880, and found on 

 the coast of Brazil (lat. 17° 30' S.) Aug. 11, 1882. 

 The distance traversed was probably 4,500 nautical 

 miles, or an average of over seven miles a day. — 

 (Id., 61.) w. M. D. [936 



Earthquakes on the Armenian plateau. — H. 

 Abich adds a chapter on earthquakes to bis geologi- 

 cal description of this region, which contains much 

 of importance concerning the volcanoes and other 

 jjliysical features of Ai'menia, with fine illustrations 

 in maps and views. The two chief seismic centres 

 are the Ararat volcanic group and the Palandokiin 

 near Erzerum. At the former, in 1840, a great land- 

 slide was produced by a shock, of which Abicli's pre- 

 vious description (Verh. gesell. f. erdk. Berlin, iv. 

 1845, 28) is liere reprinted. At the latter, on May 21, 

 1859, strong vertical and horizontal oscillations were 

 felt; and, in a few minutes after the first disturbance, 

 over a third of the town's eight thousand houses 

 were in ruins, and five hundred people were killed or 

 mortally wounded. It was noticed that heavily-built 

 houses suffered more than lighter ones, and that the 

 destruction was much greater in the central, higher 

 part of the city, which stood upon a rocky basis, than 

 in the lower suburbs on the alluvial plain. The 

 earthquake of Sbemaka, May 31, 1859, is described 

 in detail, and the general relation of the Armenian 

 with the Mediterranean vulcano-seismic disturbances 

 along the belt between latitude 37° and 40°, from 

 the Caspian to the Atlantic, is discussed. An ex- 

 tended list, compiled from old Armenian chronicles, 

 is added, showing fifty-two earthquakes from 350 

 to 1650 A.D., in many of which the destruction was 

 very great. — (Geol. forsch. kaukas. Idndern. ii., 

 geol. armeix. liochlandes, westhiXlfte. Vienna, 1882.) 

 ■w. M. D. [937 



The north German plain. — From the Straits of 

 Dover eastward, between the flanks of the Eifel, 

 Harz-, Erz-, and Riesengebirge on the south, and the 

 shore of the North Sea and the Baltic on the north, 

 the country is low and generally flat. Westward 

 from the Elbe, the plain is hardly more than 20 met. 

 above sea-level, except on the Luneberg heath, which 

 rises to 80 met. Eastward from the Elbe, the high- 

 est ground is found in lake-plateaus {seenplatte) of 

 Meclvlenburg (about lOOmet. ),Pommerania (100), and 

 Prussia (110), with plains of much less elevation and 

 more level surface, both north and south. The grad- 

 ual rise from the sea is also shown by the low levels 

 of the Rhine (36 met. ) at Cologne, 130 miles from 

 the coast; the Weser (40 met.) at Minden, 100 miles 

 inland; the Elbe (45 met.) at Magdeburg, 150 miles; 

 the Oder (20 met.) at Frankfurt, 125 miles; and the 

 Weichsel (41 met.) at Thorn, 110 miles. This flat 

 surface does not end at the shore, but continues under 

 tlie Baltic and the North Sea. In addition to the 

 stratified sands and clays whicli cover a great part of 

 this plain, it contains many large erratic bowlders 

 and unstratified deposits, which have heretofore been 

 generally considered the results of a great flood, or of 

 iceberg transport; but recently these deposits have 

 been closely examined, and witliin the past flve years 

 a large number of German geologists have found 

 reason to believe that their low northern country was 

 invaded in post-tertiary time by an ice-sheet extend- 

 ing outward from Scandinavia. Bernhardi (1832) 

 was the first to make such a supposition, but looked 

 to the polar regions for the source of the ice. After 

 him came Agassiz and Naumann (1844); but their 

 observations were overlooked, initil, in late years, 

 Berendt, Credner, Helland, Penck, and others, all 

 denied the importation of erratics by floods or by ice- 

 bergs, and contended for the action of land-ice. Their 

 results are summarized by Th. H. Schunke, briefly 

 as follows: the unconsolidated deposits of north Ger- 

 many consist, in part, of stratified sands and clays, 

 with land, fresh and marine fossils, for which no 

 explanation has been generally accepted, except that 

 it was accumulated under water; and, in part, of 

 compact, unstratified sheets of drift containing nu- 

 merous subangular stones, 90 fc of which are foreign 

 (from Scandinavia, etc.), 80 % are scratched, and, 

 many are of great size. Stones of local origin are 

 carried against the jiresent direction of river-flow, 

 and sometimes to a higher level than their source. 

 Several of the few rock ledges appearing through this 

 drift-covering have been found rounded and striated; 

 and the clayey strata that often underlie the unstrati- 

 fied drift are discovered greatly disturbed, com- 

 pressed and folded. Pot-holes are very common. 

 All this is best explained by glacial action, perhaps 

 alternating with open water and floating ice. No 

 terminal deposits are yet found, clearly marking the 

 farthest advance of the ice; but the lake-plateaus, 

 a little way inland from the Baltic coast, have all the 

 characteristics of terminal moraines. Elsewhere the 

 surface is lower and more even, being generally lev- 

 elled off with a sheet of stratified sand, or covered 

 with still more recent moors. The rivers are mod- 

 erately depressed below the general surface. It has 

 been suggested that the Weichsel and Oder were dis- 

 placed from tlieir lower courses when the ice-sheet 

 reached the ' seenplatte,' and then turned westward, 

 near Bromberg and Frankfurt, to join the Elbe above 

 Wittenberg, their old east-to-west channel being 

 much larger than the streams which now occupy it. 

 Although the action of land-ice is thus generally ad- 

 mitted, many questions are by no means settled; 

 notably, the character of tiie water-basins in which 



