906 



SCIENCE. 



[N. S. Vol. XV. No. 388. 



ures continuity of strata can be established, 

 while even in the independent synclinal trough 

 of the Georges Creek basin there is found the 

 same sequence of strata and fossils. Numer- 

 ous detailed measvired sections were described 

 in substantiation of these conclusions. 



'A Reconnaissance of Mt. Hood and Mt. 

 Adams,' by H. F. Reid. 



These mountains belong to the group of 

 volcanic cones built up mainly in Tertiary 

 times along the line of the Cascade Rainge. 

 Though probably extinct, steam and gases 

 still issue in small quantities from cracks 

 near the summits. The mountains consist 

 of massive lava and lapilli, the latter being 

 more abundant on Mt. Hood and the former 

 on Mt. Adams. Some of the later lava-flows 

 are probably not more than a few hundred 

 years old. A number of parasitic cones are 

 found on the flanks of Mt. Adams, two, at 

 least, with well-marked craters, while none 

 occur on Mt. Hood. About one half of the 

 original crater wall of Hood still remains, 

 the southern half having disappeared. The 

 summit of Adams is long and broad. The 

 stratification seen in the cliffs on the sides of 

 the mountain suggest that there were several 

 craters which may have been active at the 

 same time or successively. 



Many interesting glaciers lie on the slopes 

 of both mountains; but they do not descend 

 into the valleys. In several cases the depres- 

 sions outside the lateral moraines are appar- 

 ently quite as deep as the bed of the glaciers, 

 and the canons formed below the ends of the 

 ice are deeply eroded, in strong contrast to ice- 

 covered parts of the mountains. The main 

 erosion has been effected by water, and the 

 ice and snow, by preventing the concentra- 

 tion of the water, have protected the under- 

 lying rock. 



There is little indication of a much greater 

 extension of the glaciers of Hood in former 

 times, but on Adams glacial scratches abound 

 in positions not now reached by the ice. 



'Recent Work in the Piedmont Area of 

 Northern Maryland,' by Edward B. Mathews. 



Areal mapping of the Piedmont Plateau in 

 northeastern Maryland has been carried on 

 during the last three years by the speaker, 



Miss F. Bascom and Mr. A. Johannsen. The 

 formations present an intricate interming- 

 ling of igneous and metamorphic rocks com- 

 prising monzonites, gabbros, metarhyolites, 

 and serpentines among the igneous rocks ; and 

 gneisses, quartz-schists, phyllites and slates 

 among the metamorphosed sedimentary rocks. 



The sequence of eruptions in the region is 

 believed to include two periods, represent- 

 ing differentiated portions of an original 

 magma of medium acidity. One formed 

 the monzonites and was itself somewhat dif- 

 ferentiated during the period of consolidation, 

 monzonite; the second formed the gabbros, 

 with the accompanying quartz-gabbros, no- 

 rites and peridotites produced by secondary 

 differentiation. 



All of these have been intruded into the 

 mica-gneiss which is either of early Paleozoic 

 or pre-Cambrian age. 



'The Miocene Formation of Maryland,' 

 by G. B. Shattuck. 



In the differentiation of the Chesapeake 

 group, three well-defined formations are rec- 

 ognized, which are described from below up- 

 ward under the names of Calvert, Choptank, 

 and St. Mary's formations. An unconform- 

 ity occurs between the Calvert and the Chop- 

 tank. Well defined lithologic features mark 

 the several formations, which have been 

 mapped in great detail throughout southern 

 and eastern Maryland. Each formation has 

 its clearly defined fauna. 



'The Pleistocene Problem in Maryland,' 

 by G. B. Shattuck. 



The gravel deposits of the North Atlantic 

 Coastal Plain are divisible into five forma- 

 tions, which are known, beginning with the 

 oldest, as the Lafayette, Sunderland, Wico- 

 mico, Talbot and Recent. The Lafayette has 

 been doubtfully referred to the Pliocene; the 

 Sunderland, Wicomico and Talbot are be- 

 lieved to be Pleistocene. 



Each of these formations is developed in a 

 distinct terrace which is separated from . the 

 adjacent terraces both above and below by 

 well-defined scarps. These terraces lie one 

 above the other, the oldest occupying the 

 top of the series, and the youngest the bottom. 



The agencies which have been instrumental 



