192 14 



dome, which are now both fewer and less prominent lliaii in IScSS. On the lower 

 dome tlie thermal activity has also on the whole declined. There are, however, 

 some exceptions, the most conspicuous being Oskurholl, which has now resumed 

 ils resonant exhalations of vapour, well-known from Oi.afsson's and Henderson's 

 descriptions. Amongst other springs which seems to have increased in force since 

 1888, Nos. 16, 23 and 24 are noteworthy. It would of course be premature to con- 

 clude from the preceding observations, that the thermal activity at Hveravellir is 

 in a continual state of decline. Many of the changes noted can be traced to more 

 accidental grounds. Precipitation and other meteorological conditions have doubt- 

 less great influence on the springs, and that is at least the most plausible explana- 

 tion of Öskurhöll's changeability. 



Hut the matter presents another aspect, when one compares the springs on 

 the lower and upper domes of silicious sinter; for one must then suppose that the 

 question of meteorological influences is essentially eliminated. The accompanying 

 observations show with considerable certainty that the activity of the springs on 

 the upper dome has decreased appreciably more than on the lower dome. This 

 is in agreement with previous observations from other places, and shows that in 

 general hot springs have a tendency to find the lowest level, — a result which 

 would be reached on purely physical considerations. 



In the lava-lield Kjalhraun to the south-east of the above-mentioned springs, 

 there are considerable thermal exhalations. These exhalations are chiefly grouped 

 about an imaginary line from Hveravellir, in a southerly direction, about 43° to 

 the east. Curiously enough, Kerlingarfjöll lies in the same line, if it be produced. 

 We examined in two places the gases which thus streamed out through rifts in the 

 lava. Of these, Kjalhraun No. 1 was takeii about 110 m. south-east of the most 

 south-easterly dome of silicious sinter. The exhalations, of which the temperature 

 was 87 , produced a whistling sound as they were emitted from the holes in 

 the lava. 



Kjalhraun No. 2 was taken up in the lava about 1 kilometre south-east of 

 Hveravellir. The temperature of the exhalations was 88°. 



Our visit to Hveravellir extended over 4 days. On the 26th. July, we left 

 Hveravellir, and pitched our tent at Grànunes, whence we made excursions^ to the 

 springs at Kerlingarfjöll. It was originally our intention to camp west of Askarf)s- 

 fjall, just to the north of Kerlingarfjöll, but as the early part of the summer of 

 1906 was unusually cold in Iceland, there was not sufficient pasture at that place 

 for the horses during our stay. We were compelled therefore to choose Granuncs 

 as our camping-ground, although it was at least three limes as far away from the 

 springs. The double journey between Grànunes and the springs took more than 

 6 hours, and moreover we had to make a difficult crossing over the river Jökulkuisl. 

 We stayed at Grànunes for 6 days, but on account of unfavourable weather we could 

 only make two excursions to Kerlingarfjöll, viz. on the 28th. and 31sl. July 1906. 



