THE GEOLOGIST. 



port in the south-west portion of the island, and hurrying forward 

 inland, in an easterly direction, towards the Geysirs. Passing through 

 a variety of scenery, they come out at length to a wide plateau of 

 lava,* stretching away for miles, barren and dismal, innumerable 

 boulders— relics of the glacial period— encumbering their path. At 

 length, at a distance of about five-and- thirty miles from Eeykjavik, " I 

 was arrested (says his lordship) in full career by a tremendous preci- 

 pice, or rather chasm, which suddenly gaped beneath my feet, and com- 

 pletely separated the barren plateau we had been so painfully traversing, 

 from a lovely, gay, sunlit flat, ten miles broad, that lay — sunk at a 

 lower level by a hundred feet — between us and the opposite mountains. 

 I was never so completely taken by surprise. Sigurdr's purposely 

 vague description of our halting- place was accounted for. 



We had reached the famous Almanna Gja. Like a black rampart 

 in the distance, the corresponding chasm of the Hrafna Gja, cut across 

 the lower slope of the distant hills, and between them now slept in 

 beauty and sunshine the broad verdant plain of Thingvalla. 



" Ages ago — who shall say how long — some vast commotion shook 

 the foundations of the island, and, bubbling up from sources far away 

 amid inland hills, a fiery deluge must have rushed down between their 

 ridges, until, escaping from the narrow gorges, it found space to spread 

 itself into one broad sheet of molten stone over an entire district of 

 country, reducing its varied surface to one vast blackened level. 



" One of two things then occurred — either the vitrified mass con- 

 tracting as it cooled, the centre area of fifty square miles burst asunder 

 at either side from the adjoining plateau, and, sinking down to its pre- 

 sent level, left the two parallel Gjas, or chasms, which form its lateral 

 boundaries, to mark the limits of the disruption ; or else, while the pith 

 or marrow of the lava was still in a fluid state, its upper surface became 

 solid, and formed a roof between which the molten stream flowed on 

 to lower levels, leaving a vast cavern, into which the upper crust sub- 

 sequently plumped down." 



His lordship next proceeds to a detailed description of the 

 section, as follows : — 



Trachyte, t.c, lava in which felspar predominates. 



