198 20 



to have been in existence only for a short lime. A little to the north of this spring, 

 and higher up on the mountain slope, there is a small group of springs, which, on 

 account of its dome-shaped deposit of silica, reminds one to some extent of the 

 hot springs at Hveravellir. 



Farther to the north, and on about the same level as the mud pool previously 

 mentioned, is a rather large group of springs consisting of mud pools and solfataras. 

 The springs are situated around a powerful steam volcano, which, with an ear- 

 splitting report, throws up a strong column of steam. From this group we look 

 two gas samples: Hengill No. 1 and Hengill No. 2. No. Î is from a spring to the 

 south of the steam volcano. The spring water, which had an acid reaction, and 

 contained sulphates to a considerable extent, but no chlorides, had a yellowish 

 tint on account of deposited particles of the same colour. No. 2 comes from a 

 little spring immediately to the north of the steam volcano. 



The nearest group of springs to the north, is situated at a much greater alti- 

 tude. The distance between these groups is presumably about 600 or 700 m. In 

 the group which is seen to the left in the picture (Plate X), there are several solfa- 

 taras and mud pools, but the most peculiar is perhaps a spring with a temperature 

 of 23.3°, which lies just to the north of the group. This spring contains a large 

 volume of water, which has deposited a yellowish-white layer, about 4 or 5 cm. 

 thick, in its bed. This layer consists chiefly of precipitated sulphur, which, it 

 follows, the spring water must contain. How this sulphur is produced cannot al 

 present be decided; at any rate it does not seem probable thai it has been occasioned 

 by the imperfect combustion of sulphuretted hydrogen in the atmosphere. John- 

 STRiip's ' theory on the formation of sulphur in Iceland cannot therefore be applied 

 to this case, even though it seems in most other places to give the most feasible 

 explanation of the formation of sulphur around the solfataras. 



In a north-eastern direction from the last-mentioned group of springs, there 

 is another large gi'oup situated directly north of a high grass bank. This group, 

 ■which is seen in the foreground lo the right of the illustration (Plate X), was on a 

 level with the site of our tent, which was, according to the elevation we took, 

 300 m. above sea-level. At this place there are two large mud volcanoes, which 

 throw up mud and water incessantly to a height of about half a metre (Plate IX, b). 

 The specimen Hengill No. 3 is taken from a little spring just lo the north of the 

 mud volcano shown in the illustration. 



Some distance north of the groups of springs already mentioned, there are 

 yet three more groups. Of these the one to the extreme south-east consists almost 

 exclusively of solfataras (Plate XI). In the middle group, which is to be seen in 

 the background of the photograph, (Plate XII), we collected the specimen Hengill 

 Nr. 4. It seems that the thermal activity around this group is increasing in extent. 

 For instance, we noticed that the grass upon a little plot which in our opinion 

 must recently have been covered with grass, had mostly been destroyed by the 



' loc. cit. 



