182 Scientific Intelligence — Meteorology and Geology. 



tion of the cathedral ; and Ahlert, at that time master of the works, 

 chose the tracliyte of the Wolkenburg, from the quarries of Rhbn- 

 dorf. This stone, however, is no longer employed. The trachyte 

 of the Stenzelberg is used, in so far as it can be obtained, and is evi- 

 dently the best building stone of all the trachytes of the Siebenge- 

 birge, although it is diliicult to work, and its transport is expensive. 

 As the quarries of the Siebengebirge were not sufficient to afford ma- 

 terials for the building operations of the cathedral. Professor Ndg- 

 gerath, and Councillor Zwirner, master of works, suggested, in 

 1837, that the tracliyte quarry near Berkum, about five miles from 

 Mehlem, should be purchased for the purpose. This proposal was 

 adopted, and a considerable quantity of stone for the plainer parts of 

 the building is obtained from this quarry. Since the year 1834, a 

 trachytic rock from tiie Perlenkopf, near Hannebach, has also been 

 used ; and there may also be enumerated as materials occasionally 

 employed, the porous basalt, or the so-called millstone-lava of Nie- 

 dermendig and JMayen ; the Keuper sandstone of Heilbronn, on the 

 Neckar ; the coal formation sandstone of Flonheim, near Kreuznach ; 

 and the Bunter sandstone of Udelfangen, near Treves. A portion of 

 the interior of the cathedral has been constructed of a variety of volca- 

 nic tufa termed trass by geologists, and frequently called Duckstein on 

 the Rhine, which has been obtained from various quarries in the neigh- 

 bourhood of the Laacher-Sce. The figures and carved work of the 

 cathedral have been formed of Weiberstein, a volcanic tufa more ho- 

 mogeneous than trass, which is found near the village of AYcibeni, 

 about five miles from the Laacher-See. The columnar basalt of 

 Oberwinter has been partly employed for the foundation walls. The 

 mortar which is now used for the structure is obtained from the 

 Hcrgkalk of Paffrath and Gladbach, on the left bank of the Rhine. 

 (JFrom a Paper hy Professor No^fjerath in Karstcn's Archiv, vol. 

 xviii., p. 455.) 



5. Early Composition of the Atmosphere. — Professor H. D. 

 Rogers submitted to the Association of American Geologists the 

 following communication on the probable constitution of the atmo- 

 sphere at the period of the formation of coal : — He stated, that the 

 recent researches of American geologists, by informing us of the 

 true quantity of coal in North America, enables us, for the first 

 time, to estimate, with some precision, its total amount on the 

 globe, and thereby to compute the quantity of carbonic acid which 

 the ancient atmosphere must have contained, to supply this body of 

 carbon. He shewed, that the existing atmosphere contains, in its 

 carbonic acid, carbon enough to furnish, through vegetable action, 

 about 850,000,000,000 tons of coal ; and that the probable quan- 

 tity of coal in existence, all of which must have been elaborated 

 from the ancient atmosphere, is nearly 5,000,000,000,000 tons — 

 that is to say, about six times that which the present atmosphere 

 could produce. So great a reduction in the carbonic acid of the 



