956 



SCIENCE. 



[N. S. Vol. XI. No. 285. 



rather than the Hann, or driven, theory, best 

 explains the facts discovered. 



Anales de la Oficina Meteorologica Argentina, 

 por su Director, Gualterio G. Davis. Tomo 

 XII. Climas de Asuncion del Paraguay y Bosario 

 de Santa Fe. Segunda Parte : Discusion de las 

 Observaeiones hechas en Asuncion y Rosario. 4to. 

 Buenos Aires. 1898. Pp.297. This is one of 

 the valuable series of publications on the cli- 

 mate of the Argentine Republic which is being 

 issued by Mr. Walter G. Davis, the Chief of 

 the Argentine Meteorological Service. 



R. Dec. Ward. 

 Haevaed Univhesity. 



CUBBENT NOTES ON PHYSIOGBAPHY. 

 PHYSIOGEAPHY of MARYLAND. 



' A General Report on the Physiography of 

 Maryland,' a dissertation by Cleveland Abbe, 

 Jr., for the degree of doctor of philosophy at 

 Johns Hopkins University (Maryland State 

 Weather Service, i, 1899, 41-216), stands with 

 the account of Missouri by Marbut, of New 

 Jersey by Salisbury, and of New York by Tarr 

 as one of the few thorough studies of State 

 geography that have yet appeared in this coun- 

 try. Many items of interest might be abstracted 

 from it. For example, those concerning the 

 lower courses of the ' falls ' or young cascading 

 streams in the narrow gorges by which the Pied- 

 mont plateau is dissected for eight or ten miles 

 inland from the fall-line, and the upper courses 

 of the same streams which flow quietly through 

 shallow open upland valleys where the effects 

 of the elevation of the region are not yet felt. 

 Again, those concerning the Hagerstown (Ap- 

 palachian) valley, a well-finished and evenly 

 uplifted peneplain, now rather sharply dissected 

 by young streams in narrow meandering gorges, 

 from which it is inferred that the streams mean- 

 dered upon the valley floor before uplift of the 

 region to its present altitude (500 feet in the 

 neighborhood of the Potomac). A chapter on 

 the development of the streams of the Pied- 

 mont plateau bears evidence of the greatest pro- 

 portion of original study ; it leads to the conclu- 

 sion that the streams east of Parr's ridge (which 

 represents a low swell surmounting the former 

 lowland of the Schooley peneplain) have been 

 superposed through a cover of coastal plain 



strata that once extended further inland than 

 now. 



An introductory account of 'Physiographic 

 Processes' contains a paragraph which may 

 mislead by stating that the ridges of the Appa- 

 lachian province have been 'formed by the 

 folding and faulting of the paleozoic strata of 

 that district. ' A learner might thus be tempted 

 to compare them with the young unsculptured 

 mountain blocks of southern Oregon ; yet, as 

 indeed appears from other pages of the Report, 

 the Appalachian ridges of to-day are as truly 

 forms of circumdenudation as are the low hills 

 of the coastal plain or the high hills of the 

 Allegheny plateau. 



THORODDSEN ON ICELAND. 



Thoroddsen has prepared a most interesting 

 summary of his eighteen years of exploration 

 in Iceland (ffeo^rr. Journ., xiii, 1899,251-274, 

 480-513). The island, 40,450 square miles in 

 area, is the dissected remnant of a basaltic 

 plateau, averaging 2000 feet in altitude, and 

 for the most part barren and uninhabitable. 

 Non-marine tertiary strata are intercalated 

 within the basalt sheets, and a ' pelagonite brec- 

 cia '* overlies them on a third of the surface. 

 Deep valleys and fiords have been eroded in 

 the margin of the plateau, where coast clifis 

 rise 2000 or 3000 feet ; but in the interior the 

 relief is less pronounced. Relatively modern 

 lavas have been poured out abundantly on the 

 plateau, building mountains, filling valleys, 

 displacing rivers and altering the coast line. Of 

 107 volcanoes counted in a certain district, 8 

 were large lava and ash cones of the Vesuvian 

 type, 16 were large flat domes of the Mauna 

 Loa type, and the remainder were small ash 

 cones arranged in chains along fissures. The 

 summits of the domes, 2000 or 3000 feet in 

 height over the plateau, are broken by large 

 craters (calderas ?) containing frozen lava lakes ; 

 many lava tunnels are found on the slopes of 

 the domes, whose inclination is seldom more 

 than 7'^ or 8°, and may be much less. The 

 small ash cones may be as steep as 30° and oc- 

 casionally 40° or even 50° : one chain contains 



* This formation has lately been interpreted as of 

 ancient glacial origin by H. Pjetersaon. Scot. Geogr. 

 Mag., xvi, 1900, 265-293. 



