VAUX VOLCANIC ROCKS OF ICELAND. 



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1. Gjas. 2. Lava deluge. 3. Original surface. 4. Thing\ alla sunk, to a lower level. 



1, 1 " are the two chasms, called respectively Almanna Gja, or Main 

 Gja, and Hrafna Gja, or Kaven's Gja. In the act of disruption the 

 sinking mass fell in, as it were, upon itself, so that one side of the Gja 

 slopes a good deal back as it ascends ; the other side is perfectly per- 

 pendicular, and, at the spot I saw it, upwards of a hundred feet high. 

 In the lapse of years, the bottom of the Almanna Gja has become gra- 

 dually filled up to an even surface, covered with the most beautiful 

 turf, except where a river, leaping from the higher plateau over the 

 precipice, has chosen it for a bed. You must not suppose, however, 

 that the disruption and land-slip of Thingvalla took place quite in the 

 spick and span manner the section might lead you to imagine ; in some 

 places the rock has split asunder very unevenly, and the Hrafna Gja 

 is altogether a very untidy rent, the sides having fallen in in many 

 places, and almost filled up the ravine with ruins. On the other hand, 

 in the Almanna Gja, you can easily distinguish on the face marks and 

 formations exactly corresponding, though at a different level, with 

 those on the face opposite, so cleanly were they separated. 



" 2 " is the sea of lava now lying on the top of the original surface. 

 Its depths I had no means of ascertaining. 



" 3 " is the level of the surface first formed when the lava was still 

 hot. 



" 4 " is the plain Thingvalla, eight miles broad ; its surface shattered 

 into a network of innumerable crevices and fissures, fifty or sixty feet 

 deep, and each wide enough to have swallowed the whole company of 

 Corah. At the foot of the plain lies a vast lake, into which indeed it 

 may be said to slope, with a gradual inclination from the north, the 

 imprisoned waters having burst up through the lava strata as it sub- 

 sided beneath them. Gazing down through their emerald depths, you 



