quarried it is ground in
mills, and used for cement stone under the name of _trass_. It is said
to resemble the volcanic mud by which Herculaneum was overwhelmed during
the first eruption of Vesuvius, and which was produced by the torrents
of rain mixing with the ashes as they were blown out of the volcano.

Sufficient has probably now been written regarding the dormant, or
recently extinct, volcanic districts of Europe to give the reader a
clear idea regarding their nature and physical structure. Other
districts might be added, such as those of Central Germany, Hungary,
Transylvania, and Styria; but to do so would be to exceed the proposed
limits of this work; and we may therefore pass on to the consideration
of the volcanic region of Syria and Palestine, which adjoins the
Mediterranean district we have considered in a former page.

[1] Daubeny, _loc. cit._, p. 71. The geology of this region has had many
investigators, of whom the chief are Steininger, _Erloschenen Vulkane in
der Eifel_ (1820); Hibbert, _Extinct Volcanoes of the Basin of Neuwied_,
1832; Noeggerath, _Das Gebirge im Rheinland_, etc., 4 vols.; Horner, "On
the Geology of Bonn," _Transactions of the Geological Society, London_,
vol. iv.

[2] The views of Dr. Hibbert are not inconsistent with those of the late
Sir A. Ramsay, on "The Physical History of the Valley of the Rhine,"
_Quart. Jour. Geol. Soc._, vol. xxx. (1874).

[3] Von Dechen, _Geog. Beschreib. des Siebengebirges am Rhein_ (Bonn,
1852).

[4] Hibbert, _loc. cit._, p. 18.

[5] Horner, "Geology of Environs of Bonn," _Transactions of the
Geological Society_, vol. iv., new series.

[6] H. von Dechen, _Geog. Fuehrer in das Siebengebirge am Rhein_ (Bonn,
1861).

[7] _Ibid._, p. 191.

[8] Dr. Hibbert's work is illustrated by very carefully drawn and
accurate views of some of the old cones and craters of this district,
accompanied by detailed descriptions.

[9] The lava of Schorenberg, near Rieden, is interesting from the fact,
stated by Zirkel, that it contains leucite, nosean, and nephelin.--_Die
Mikros. Beschaf. d. Miner. u. Gesteine_, p. 154 (1873).

[10] Hibbert, _loc. cit._, p. 23.

[11] At the time of the author's visit the underground caverns, which
are deliciously cool in summer, were used for the storage of the
celebrated beer brewed by the Moravians of Neuwied.

[12] Hibbert, _loc. cit._, p. 129.

PART III.

DORMANT OR MORIBUND VOLCANOES OF OTHER PARTS OF THE WORLD.