124 SEFSTROM ON THE FURROWS WHICH TRAVERSE 
wise level piece of ice, will give rise to a large snow-drift of the 
most remarkable form. There are, besides, banks of sand and 
gravel of inexplicable shapes continually forming, even under 
our eyes, in streams and by great floods. 
§ 13. 
Of the Force which caused the Boulder-flood. 
The ultimate cause of this force will probably for ever be 
concealed from our researches. This knowledge belongs alone 
to Him who shaped the world, and whose causes are always 
proportioned to the object to be effected; these we can generally 
afterwards see, but for this a long time is requisite. In this 
manner we now discover, that however destructive it might ap- 
pear to us mortals for such a flood to have passed over the 
earth, yet we find that if this had not occurred, if it had not 
reduced a great part of the surface of the earth to gravel, sand, 
and mould, it would have consisted only of crags on which 
nothing could exist; being incapable of sustaining vegetation, 
neither animals nor man could have resided upon it. 
But if it is not permitted for us to see the first cause of this 
force, we need not nevertheless give up the hope of being able 
to find out its nature. 
When we see that the boulders have been in motion against 
the fast rocky surface of the mountains, and that the former 
have struck with a considerable force against the latter, two 
probable suppositions offer themselves as to the manner in 
which this manifestation of force might have arisen: either, that 
the boulders were thus, by some exterior force, set in motion 
towards the surface of the earth, which in relation to them was 
at rest; or else, that the earth was moved in a direction accord- 
ing to which the boulders were relatively at rest. 
The arguments in favour of the hypothesis of a change in the 
position of the earth’s axis and velocity of rotation, and the 
consequent effect on the precession of the equinoxes, as well 
as the opposing arguments, are sufficiently well known, but are 
not of such a nature as to offer any encouragement to our 
adding this hypothesis to the number of existing theories. 
We will therefore limit ourselves to this question only,— 
whether any indication is to be found which will show whether 
