86 
LETTERS FROM HIGH LATITUDES. 
vast cavern into which the upper crust subsequently 
plumped down. 1 
The enclosed section will perhaps help you a little 
to comprehend what I am afraid my description will 
have failed to bring before you. 
1 Gjas„ 2 Lava deluge. 3 Original surface, 
4 Tliingvalla sunk to a lower level. 5 Astonished traveller. 
1 I feel it is very presumptuous in me to hazard a conjecture on a 
subject with which my want of geological knowledge renders me 
quite incompetent to deal; but however incorrect either of the above 
suppositions may be justly considered by the philosophers, they will 
perhaps serve to convey to the unlearned reader, for whose amuse¬ 
ment (not instruction) these letters are intended, the impression 
conveyed to my mind by what I saw, and so help out the picture 
I am trying to fill in for him. 
