114 SEFSTROM ON THE FURROWS WHICH TRAVERSE 
there is a circumstance which prevents its ever properly suc- 
ceeding, namely, that the boulders were surrounded by gravel 
and sand, which, along with the water, prevented their free de- 
scent, and makes all calculation impossible. 
A hope was afterwards entertained that on the eastern or 
western end of some level rock we might be able to follow a fur- 
row to a much greater distance, in order to see how much it had 
sunk in a certain length; but even this hope was disappointed ; 
and, had it succeeded, the calculation nevertheless would be al- 
ways difficult whilst the friction is unknown. 
§ 8. 
How long the Boulder-stream may have continued. Was it 
uninterrupted ? 
The hope of receiving an answer to these questions has al- 
ways been, and still continues, very feeble. Nevertheless it is 
possible to determine within what limits we are to look for the 
answer to the former question. From some phenomena we may 
ascertain thus much, that this flood was not one that quickly 
subsided, or suddenly ceased. 
The first reason for the hypothesis that it continued for a 
long period is this,—that it could crush enormous masses of hard 
rocky substances, such as gneiss and granite, to a fine sand, with 
which whole countries of Europe are covered, often to a con- 
siderable depth. Nevertheless these accumulations of sand are 
very inconsiderable in comparison with those which form the 
banks at the bottom of the sea. Besides, it is not improbable 
that the masses of sand which constitute the great deserts of 
Africa and Asia also are the produce of such a flood, which 
thus could not have quickly subsided. 
The second reason for concluding that it lasted for a long time 
is drawn from the phenomenon known by us under the name 
of Jattegrytor (giant-caldrons), or spheroidical hollows in the 
solid rocks, which are described by Thorbern Bergman in dess 
Fysiska beskrifning om Jordklotet, § 150*, and in most cases 
must be the relics of the boulder-flood ; I say, in most cases, 
for there are giant-caldrons which are made by the usual ope- 
ration of our rivers. Such are those near Avesta; and I saw 
* Bergman’s Natural History of our Globe. 
