MAA.RS. 227 



most brilliant discoveries of our time, have their principal 

 seat in the volcanic Eifel, in the Rapilli, Trass strata, and 

 pumice conglomerates. Organisms with silicious shields fill 

 the valley of Brohl and the eruptive matters of Hochsim- 

 mer; sometimes, in the Trass, they are mixed with uncar- 

 bonized twigs of coniferae. According to Ehrenberg, the 

 whole of this microcosm is of fresh-water formation, and 

 marine Polythalamia* only show themselves exceptionally 

 in the uppermost deposit of the friable, yellowish loess at the 

 foot and on the declivities of the Siebengebirge (indicating 

 its former brackish coast nature). 



Is the phenomenon of Maars limited to Western Germa- 

 ny ? Count Montlosier, who was acquainted with the Eifel 

 by personal observations in 1819, and who pronounces the 

 Mosenberg to be one of the finest volcanoes that he ever saw 

 {like Rozet), regards the Gouffre de Tazenat, the Lac Pavin 

 and Lac de la Godivel, in Auvergne, as Maars or craters of 

 explosion. They are cut into very different kinds of rock 

 in granite, basalt, and domite (trachytic rock), and surround- 

 ed at the margins with scoriae and rapilli.f 



The frame-works, which are built up by a more powerful 

 eruptive activity of volcanoes, by upheaval of the soil and 

 emission of lava, appear in at least six different forms, and 

 reappear with this variety in their forms in the most distant 

 zones of the earth. Those who are born in volcanic districts, 

 among basaltic and trachytic mountains, are often genially 

 impressed in spots where the same forms greet them. Mount- 

 ain forms are among the most important determining elements 

 of the physiognomy of nature they give the district either a 



* Upon the antiquity of formation of the valley of the Khine, see 

 H. von Dechen, Geognost. Heschreibung des Siebengebirges, in the Vcr- 

 handl. des Naturhist. Vereins dcr Preuss. Rheinlande und Westphakns, 

 1852, s. 556-559. The infusoria of the Eifel are treated of by Ehren- 

 berg in the Monatsber. der Akad. der Wis's. zu Berlin, 1844, s. 337 ; 

 1845, s. 133 and 148; and 1846, s. 161-171. The Trass of Brohl, 

 which is filled with crumbs of pumice-stone containing infusoria, 

 forms hills of as much as 850 feet in height. 



f See Rozet, in the Memoires de la Societe Geologique, 2me serie, t. 

 i., p. 119. On the island of Java also, that wonderful seat of multi- 

 farious volcanic activity, there occur "craters without cones, as it were 

 flat volcanoes" (Junghuhn, Java, seine Gestalt und Pflanzendeckc, Lief, 

 vii., p. 640), between Gunung Salak and Penvakti, analogous to the 

 Maars as " craters of explosion." Destitute of any elevated margins, 

 they are situated partly in perfectly flat districts of the mountains, 

 have angular fragments of the burst rocky strata scattered around 

 them, and now only emit vapors and gases. 



