Von Nidda on the Mineral Springs of Iceland. 225 



The spring of Buderstadt has a. temperature of 6 R. (45^ F.), 

 and in composition resembles extremely the preceding. 



The springs which are so unusually frequent in Iceland, viz. 

 those characterized by a high temperature, by their containing 

 silica in solution, and by their giving out sulphuretted hydrogen 

 gas, are entirely a wan ting in the volcanic promontory of the 

 Sneefield-Syssel. This is certainly a remarkable circumstance, 

 as we meet with this description of mineral waters everywhere 

 in those portions of the island, where volcanic activity has mani- 

 fested itself until a modern epoch by the eruptions of the vol- 

 canic chimneys. The promontory of the Sneefield-Syssel is one 

 of these districts, for it presents numerous volcanic cones, some of 

 which have been in a state of activity in modern times. The 

 fact is, that this volcanic promontory did possess hot springs which 

 contained dissolved silica. We find at many points siliceous in- 

 crustations, in the form of tuffs and sinters. The spring of 

 Lisiehuls occupies the place of one of those siliceous springs ; 

 but its present deposits are only calcareous, and are entirely dif- 

 ferent from the deeper lying siliceous incrustations. 



Are we to regard these carbonic acid mineral springs as the 

 weak remains of the more powerful displays of volcanic activity 

 of earlier periods ? 



It would lead us too far to enumerate the remaining mineral 

 springs which are dispersed over the trap district. They may 

 be the more easily omitted, as they are of insignificant magni- 

 tude, and are not in any degree to be compared with the gigantic 

 aqueous eruptions, occurring in such abundance in the trachytic 

 volcanic district. There are some isolated weak siliceous springs 

 in the deep valleys and fiords of the north coast, but in the trap 

 hills of the east coast they are entirely awanting. 



One portion only of the trap region must be instanced, from 

 its containing so large a number of springs as to entitle it in this 

 respect to be compared with the trachytic district. It is that 

 flat portion of the island traversed by several parallel valleys, 

 which is bounded on the south by the mountains of Skardsheide, 

 on the north by the chain of the Sneefield-Syssel, and on the 

 west by the Borgar-fiord. The valleys of this plain, separated 

 from one another by low rocky ridges consisting of layers of 

 trap rocks, extend in a direction from east to west, and are pa- 



