TT. G. Locke — Volcanic History of Iceland. 213 



from a rift in a subterranean channel connected with the volcano, 

 at a spot distant therefrom twenty-five miles. I compute the bulk 

 of the lava-flood that then issued at 36,000 of millions of cubic feet, 

 the bed being between twelve and thirteen miles in length, from one 

 to three in breadth, and varying in thickness from 300 to 37 feet. 



It may be remembered that Mr. Wm. Lord Watts was the first 

 Englishman, and indeed the first stranger, to visit AsJga, and that he 

 was so fortunate as to do so during the 1875 eruption. Upon his 

 return he gave a short, but very imperfect, description of the 

 volcano in a paper read before the Eoyal Geographical Society, 

 likewise in a little work entitled " Across the Vatna Jokull." Mr. 

 Watts's imperfect description is not to be wondered at, exploration 

 being next to impossible at the time of his visit, immense masses 

 of the mountain breaking away beneath his very feet. However, 

 notwithstanding that five years have elapsed, it is the only account 

 of the volcano that has been published in this country. 



Mr. Watts speaks of AsJcJa being inclosed with "sections of 

 mountains," and Herra Thoroddsen writes that the Dyngjufjoll are 

 "a complex of mountain-peaks rising up to 4500 feet high, inclosing 

 the circularly formed valley called Askja." 



This description does not convey a correct idea of these mountains, 

 and Ashja. The Dyngjufjoll {fjoll plural oi fjall = to the 'Norsk fjeld) 

 is the name given to a large mountain, whose outer circumference, at 

 an altitude of 3500 feet (where it rises somewhat abru]3tly from a 

 gentle slope formed of a succession of lava-flows which welled forth, 

 in all probability, from Ashja before the higher part of the moun- 

 tain, which now incloses that crater, was built up by the upheaval of 

 the masses of tuff" and basaltic-lavas of which it is composed), exceeds 

 twenty-four English miles, and a number of comparatively small 

 semi-detached peaks stretching northward for several miles from 

 the chief of the gi'oup. Within this large mountain lies Ashja, 

 which is unmistakably a crater ; if being the outlet of a volcanic 

 vent whence lava-flood after lava-flood has issued, both before and 

 since the higher parts of the mountain were built up around the 

 outlet, entitles such a place to that name. 



The present floor of the crater consists of rugged beds of lava 

 that have forced their way through earlier and more evenly deposited 

 ones, and lies somewhat over 2200 feet above the level of the plain, 

 1500 feet, in which the mountain stands =3700 feet above sea-level ; 

 and the crater's encircling mountain-wall is bi'oken by gaps to the 

 level of the surface lava in Aslc/a in tioo places only ; there is 

 nowhere a gap or break in the mountain from the floor of Ashja to 

 the level of the plain of the 0' darSahraun to divide it into sections, 

 therefore it is really a mountain, not a compound of mountains, and 

 is indeed so shown upon the Danish map of Iceland published 

 last year. The crater's encircling mountain-wall rises abruptly 

 from the surface lava to heights varying from 800 to 1500 feet,= 

 4500 to 5200 feet above sea-level. 



The " ' dip ' in tlie earth 750 feet ' down ' " in the south-eastern 

 part of Ashja is an oval basin-like hollow formed by the subsidence 



