[70 
a row from the S.W. corner of Vatnajskull for a distance of about 
30 km. These were caused by the eruption of 1783, the one which 
holds the record of being the greatest and the most destructive out- 
break ever witnessed in Iceland. 
CAVES 
Surtshellir and Vidgelmir. These two caves lie some 8 km. apart 
(see p. 174) and are very similar in size. Each being more than 1500 
m. long, over 10 m. high and some 12 m. wide on an average. As to 
the formation of stalactites and stalagmites, pillars of ice etc. Vidgelmir 
will probably be found the most interesting of the two. 
HOT SPRINGS 
The hot springs in Iceland, or fountains, both of boiling and warm 
water, are quite innumerable and are found at every possible altitude 
up to 1500 metres above sea level, among the icefields and down 
on the coast, where some of them are visible only at low-tide. They 
are, practically speaking, spread all over the island; at some places 
there may be seen a solitary spring issuing its vapours, but at other 
places a whole group, consisting of no less than fifty. 
At some of the hot springs there are found fairly extensive sulphur 
deposits, but all such places are situated at a great distance from any 
good harbour. 
Neither Great Gepsir nor Strokkur have been active for several 
years now, but a small geysir called Smidur, lying close by, can al- 
most invariably be made active if baited with soap, each spout reach- 
ing the height of 6 to 8 m. Blesi is the name of one of the springs 
in the Great Geysir group. It is a big twin pool almost boiling and 
always brimful of transparent blue water of great depth. 
The hot springs at Repkir, Olfus, are very varied as to form, colour 
and size, and present quite an interesting sight. Of the geysirs there, 
the one called Gryla is the most powerful, and spouts occasionally to 
the height of several metres. 
RIVERS 
Several of the Iceland rivers rank among the very best in Europe 
for salmon fishing. Some of them are also fairly good for char and 
trout fishing, but many of the lakes are particularly good for these 
last two. (See Angling pp. 174—176). 
According to the latest calculations the total amount of water power