parts of the Dee. This _détour_ having taken up more time than I
expected, I reached Brohl, late, but in time for the supper at the
rustic Gasthoff, which, with a flask of Rhenish wine, and the company of
an agreeable German tourist who was staying there, made ample amends for
the fatigues of the day.

In setting out from Brohl by the stream of the same name, which runs
down from the Lake of Laach, where I was struck with the pieces of
pumice-stone, and the charred remains of herbs and stalks of trees
scattered over the marshes. I soon came to the valley, the sides of
which are composed of what is called, in the language of geology,
_tufa_, and in that of the country, _dukstein_, or _trass_. It is a
stone, or a hard clay, of a dull blueish colour, and when dry, it
assumes a shade of light gray. An immense quantity is quarried
throughout the valley, and is sent down the Rhine to Holland, where it
is in great request for building. The village of Nippes owes its origin
to the trade in trass, having been founded by a Dutchman, who settled
there about a century ago for the convenience of exportation. The lower
part of the mass is the hardest and most compact, and is therefore
preferred by the quarrymen; as it rises, the upper part becomes loose
and sandy, and unfit for use. You must not suppose the stream to be
clear like the Aar, for it is as thick as pea-soup, and about the same
colour, being in fact a river of trass in solution. The banks, however,
are picturesque and well wooded, particularly at Schweppenbourg, an old
castle of peculiar architecture, built on an elevated rock, and formerly
belonging to the family of Metternich, (God save the mark!) The tower is
surrounded with caverns and halls, hollowed out of the trass stone, and
profusely ornamented with fine oaks, pines, and spreading beech trees.
You may almost fancy yourself on magic ground, and looking on a fairy
castle, so peculiar is the effect. I next reached Burgbrohl and