DR BOUE' ON THE GEOGNOSY OF GEllMANY. 103 
lous rocks, which, notwithstanding that they pass into sand-, 
stones, have so little of their appearance, that they receive 
other names, Claystone Tuff, Lydian-stoue, Jasper, &c. ; 
and indeed their varieties are so numerous, that there is no 
nomenclature large enough for them. 
These porphyries of the red sandstone and coal forma- 
tion are associated with many trap-rocks, which are dis- 
tinctly pyroxenic or basaltic, although the trap-rocks 
which accompany the crystalline deposits in the grey- 
wacke appear sometimes to be much more difficultly 
recognised as such. Yet, near Prague, I have seen in 
transition-slate, beds or masses of well-marked dolerite, 
having the common igneous accidents in their upper and 
under part. The same appearance I had also the pleasure 
of observing in the valley of Triebisch, near Freyberg, in 
transition clay-slate. 
The trap-rocks form in the Floetz Period, as in the 
Transition, more commonly veins, with, or without, small 
coulees^ or a kind of beds, than hills. The accidents of 
the neighbouring rocks are various. I shall only mention 
here, that, at Planitz, I observed sandstone- slate, or 
slate-clay, much indurated under the amygdaloid, and be- 
sides the amygdaloid contained an immense quantity of 
pieces of the old red sandstone, so that the whole had pretty 
nearly the appearance of an extent of mica^slate, with gra- 
nitic veins, like those of Garviemore. Besides, I have ob- 
served there, that a part of the amygdaloid was only an 
altered sandstone ; and, for this reason, many of the amyg- 
daloid s do not give pyroxene by the analysis. How such a 
change can be produced, I do not know ; but such is the 
fact, and every body may see it. I am only astonished 
that it has not been recorded. Indeed, I can assert, that 
the Erzgebirge contains many interesting facts, and distinct 
