Geology. 323 



by Palache, and the interesting fact is brought out that in five 

 recurrent periods of eruption the sequence has invariably been, 

 andesite, basalt, rhyolite in each period. This is harmonious 

 in principle, if not in exact detail, with the general laws regard- 

 ing the succession of eruptive magmas as observed in other areas. 



l. v. p. 



6. Gesteine der EcuatorianischenOst-Cordillere, Der-Cotopaxi 

 and die umgebenden Vidkanberge ; von A. Young. (Reiss <fc 

 Sttibel : Reisen in Siid Amerika. Hochgebirge der Repub. Ecua- 

 dor II Petro. Untersuch. 2 Ost. Cord. Berlin, 1902, 4°, pp. 275, 

 4 pi.). — This work, offered as an inaugural dissertation for the 

 doctor's degree, is a further continuation of the series of investi- 

 gations being carried on in the mineralogical-petrographical 

 department of the University of Berlin, under the supervision of 

 Prof. Klein, upon the material brought back by Reiss and Sttibel. 



The first half of the work contains a detailed account of the 

 topography and physiography of the well known volcano of 

 Cotopaxi. Its history, its varied outbreaks, its geological rela- 

 tions, the effect of erosion and its glaciers and glaciation are 

 fully treated. This part is by W. Reiss. 



The petrographical portion, by Young, consists of a detailed 

 and careful study of the various lavas, rock types, which are all 

 comprised under the heads of dacites, andesites of various kinds 

 and basalts. The descriptions are accompanied by a number of 

 analyses. While the rocks described are of well known types, 

 the work is, on the whole, a decided addition to our knowledge of 

 the Andean rooks. l. v. p. 



7. Der grosse Staubfall vom 9. bis 12. Marz, 1901, in Norda- 

 frik, Sud- und Mitteleuropa ; von G. Hellmann und W. Mein- 

 ardus. Abhandl. k. pr. Meteorol. Instituts., Bd. II, No, 1. 

 Berlin, 1901. — Some years ago, Ehrenberg maintained that the 

 dust falls of Europe were derived from South America. This 

 idea never gained general acceptance, and it is now completely 

 disproved for the remarkable dustfall of March 9-12, 1901, con- 

 cerning which the above cited memoir presents abundant and 

 convincing data. Dust storms were observed in the Algerian 

 Sahara during the days immediately preceding the dustfall in 

 Europe, and a stormy sirocco prevailed over the Mediterranean ; 

 North of the Alps, direct observation at mountain observatories 

 and the computed gradients at a level of 2500 met. indicated the 

 prevalence of a southerly current moving at a rate of 70 kilom. 

 an hour; and this rate agrees with that of the extension of the 

 area over which dust spread. In the south, the dust fell from 

 the dry sirocco ; in the north it came down with rain and snow. 

 The composition of the dust, prevailingly quartz, was such as the 

 Sahara might furnish. Larger and heavier grains were collected 

 in the south than in the north. In north Germany the quartz 

 grains averaged 1 : 3,200,000,000 gram in weight. The total 

 quantity of dust imported on this occasion from the Sahara is 

 estimated at about 2,000,000 tons. w. m. d. 



