ion, without folding, has raised these Pliocene
deposits to a considerable height--in some cases over 3000 ft. and they
now lie almost undisturbed upon the older folded beds. This last
elevation led to the formation of numerous lakes which are now filled up
by Pleistocene deposits. Both volcanic eruptions and movements of
elevation and depression continue to the present day on the shores of
the Tyrrhenian Sea. In the northern Apennines the elevation of the sea
floor appears to have begun at an earlier period, for the Upper
Cretaceous of that part of the chain consists largely of sandstones and
conglomerates. In Calabria the chain consists chiefly of crystalline and
schistose rocks; it is the Mesozoic and Tertiary zone which has here
been sunk beneath the sea. Similar rocks are found beneath the Trias
farther north, in some of the valleys of Basilicata. Glaciers no longer
exist in the Apennines, but Post-Pliocene moraines have been observed in
Basilicata.

REFERENCES.--G. de Lorenzo, "Studi di geologia nell' Appennino
Meridionale," _Atti d. R. Accad. d. Sci, Fis. e Mat._, Napoli, ser. 2,
vol. viii., no. 7 (1896); F. Sacco, "L' Appennino settentrionale,"
_Boll. Soc. geol. Ital._ (1893-1899). (P. La.)

FOOTNOTES:

[1] The ancient Via Aemilia, built in 109 B.C., led over this pass,
but originally turned east to Dertona (mod. _Tortona_).

[2] There are two separate lines from Sampierdarena to Ronco.

[3] This pass was also traversed by a nameless Roman road.

[4] This river (anc. Aesis) was the boundary of Italy proper in the
3rd and 2nd centuries B.C.

[5] The Monte Conero, to the south of Ancona, was originally an
island of the Pliocene sea.

APENRADE, a town of Germany in the Prussian province of Schleswig,
beautifully situated on the Apenrade Fjord, an arm of the Little Belt,
38 m. N. of the town of Schleswig. Pop. (1900) 5952. It is connected by
a branch line with the main railway of Schleswig, and possesses a good
harbour, which affords shelter for a large carrying trade. Fishing,
shipbuilding and various small factories provide occupation for the
population. The town is a bathing resort, as is Elisenlund close by.

APERTURE (from Lat. _aperire_, to open), an opening. In optics, it is
that portion of the diameter of an object-glass or mirror through which
light can pass free from obstruction. It is equal to the actual diameter
of the cylinder of rays admitted by