132 SEFSTROM ON THE FURROWS WHICH TRAVERSE 
situated for such observations, being isolated on a large level 
plain. It bears undoubted traces, which are not to be mistaken, 
of the violent course of the boulder-flood from north to south ; 
but the stratum, composed of siliceous slate, is in part so hard 
that it could not be furrowed by the boulders of gneiss, trap, 
sandstone, and clay-slate, passing over it, more especially as 
clay-slate forms the greatest part of these boulders; it is in 
part also fractured in such a manner, that one cannot imme- 
diately discern in which direction the resisting and lee-sides lie. 
The probability is, that the flood had from ten to fifteen degrees’ 
variation to the south-west. Around Prague, as well as on the 
road to that place, we meet with boulders evidently of a 
northern origin. The most remarkable among them are a spe- 
cies which are met with between Tabor and Neuhaus, and which 
consist almost entirely of pure quartz, from the size of a grain 
of sand to that of a man’s head. Every place is full of them, 
and this district is on both sides pretty clearly defined. The 
original situation of this quartz is in the northernmost point of 
Bohemia, around Friedland, where the high mountain Jeschen, 
south-west of Reichenberg, consists almost wholly of such quartz; 
and these boulders extend still further southward, east of Bud- 
weis, in the district of Béhmisch-Grazen, where several glass- 
houses are situated, on account of the easy access to this quartz. 
Linz in Upper Austria, 26th June, 18386. 
Since I last had the honour of addressing you, I have had an 
opportunity, between Vienna and Steyer, whilst on a journey to 
the mines in Lower Austria and Styria, of making some obser- 
vations on the furrows and their course in the alpine districts of 
Austria, which I wish to have added to those which I before have 
had the honour to communicate on this subject. 
As is well known, these Alps are composed principally of the 
peculiar kind of limestone, which at one time was called Alpine 
limestone, but has latterly begun to be considered as corre- 
sponding to the lowest part of the Jura limestone. From what 
I recollected of my former visit to these Alps, and my impres- 
sion that they consisted of a collection of pyramidal mountain 
masses, with steeply inclined or often perpendicular precipices, 
I had little or no hope of finding furrows here. It is also known 
from geological works, that boulders do not occur here. But 
al 
even at a short distance from Vienna, you find not only — 
